91Èȱ¬

I've been investigating news emerging from Denmark of a case of resistance to the antiviral Tamiflu - the main weapon against H1N1 swine flu.

If a resistant strain of H1N1 swine flu starts circulating it would be a concern. Britain has invested a huge amount in its stockpile of Tamiflu and will eventually have enough to treat eight in 10 of the population.

If it doesn't work in many people that would be a setback, but remember that the vast majority of people who've been infected with H1N1 swine flu have had a self-limiting illness and have overcome it without antivirals.

If resistance emerges it would also mean that the virus is mutating (as all flu viruses do) and there may be questions about what other surprises it might have in store in the months ahead.

So what actually happened in Denmark?

David Reddy, Roche's pandemic taskforce leader, said although Tamiflu-resistant isolates had been obtained from a patient it looks as though this was drug-induced.

This means that the virus developed resistance while the patient was taking Tamiflu. There were other patients in the same cluster outbreak and no resistance to Tamiflu was found in any of them.

The phenomenon of drug-induced resistance is quite different from having a Tamiflu-resistant strain in circulation. By contrast there has been a Tamiflu-resistant strain of H1N1 seasonal flu in circulation since 2008.

"There is no sign yet of a Tamiflu resistant strain (of H1N1 swine flu) circulating" said Mr Reddy. "We fully expect to see more cases where the virus may begin to develop resistance while people are taking the drug."

This is the statement that Roche has put out:

Roche is providing comment on the report of an oseltamivir resistant isolate of an influenza A(H1N1) obtained from a single patient in Denmark. Roche reiterates that such resistant isolates in people on the drug is to be expected, as resistance at a rate of 0.4% and 4% was observed in adult and paediatric populations respectively in the phase III studies.[1]

It is therefore expected that in some patients receiving antiviral medication, resistant virus will emerge. However, it is important to note that this does not mean that the currently circulating pandemic influenza A(H1N1) virus is resistant. Ongoing testing shows that other currently circulating pandemic virus remains susceptible to Tamiflu.

Communications from Denmark indicated that this was not unexpected and was not a reason to change recommendations on the use of Tamiflu. WHO recommendations remain unaltered.

In addition to monitoring by government agencies, WHO and other public institutions, Roche recently initiated the global Influenza Resistance Information Study (IRIS), which will include 1,200 patients per influenza season from 2008-2011 and will assess the clinical impact of naturally-occurring and drug-induced resistance to antiviral drugs.

Roche also continues to support the activities of the Neuraminidase Inhibitor Susceptibility Network.

[1] Aoki FY, Boyvin G and Roberts N. Influenza virus susceptibility and resistance to oseltamivir. Antivir Ther 2007; 12:603-616

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The sun has been shining, the temperature rising, and it really does feels like summer. So it's not the traditional time one would expect a flu virus to flourish.

UV light cooks the viral goose pretty quickly, and people are outside more, rather than being huddled together swapping germs (let's not spoil this theory by mentioning air conditioning or public transport).

But the H1N1 swine flu virus is not like seasonal flu.

It's sufficiently novel and contagious that it is continuing to spread despite the warmer weather. Let's look at what's happening in the UK and USA.

The number of cases of swine flu in the UK has doubled in a week. Laboratory confirmed cases stand at 4,322. today with 535 new cases, most of them coming because of a surge in London and the west Midlands.

Both areas now have more cases than the whole of Scotland, where the virus continues to flourish in the Glasgow area.

With the virus now very firmly established in London, it's likely that further big increases will follow. And remember that many cases are going unreported.

Does that mean a peak in cases - a full-blown national epidemic - will come earlier than expected, perhaps in late August or September? Possibly, but the expectation is that once the school holidays begin, there could be a pause with a peak coming from autumn onwards.

Then we could see tens of thousands of cases a week and every part of the UK will be affected. At present, in Wales, north-east and north-west England, there's still hardly any flu at all, so the virus is still not fully embedded here.

Now to the United States. has given another of its very helpful briefings to journalists.

Dr Anne Schuchat set out the situation there: 27,717 laboratory-defined cases with more than 3000 hospitalisations and 127 fatalities.

"This virus is not going away," she said, "and the reported cases are the tip of the iceberg. We are estimating there have been at least one million cases in the United States - not perfectly accurate but a ball-park figure."

That estimate is based on some telephone polls asking people whether they'd had flu-like symptoms in the past three weeks (not the most accurate way of estimating illness) and some community surveys which suggested 6% of people in hot-spot regions may have had the virus.

While not terribly accurate, the CDC appears confident that at least one million Americans have been infected.

If so, that is very reassuring news because it means the fatality rate is really very low. North America is about a month or so ahead of the UK with its outbreak so what happens there is a good guide to what may happen here.

So who is getting H1N1 swine flu in the US? Dr Schuchat said the virus was affecting mainly younger people rather than the elderly and made these points:

(1) nearly 80% of those hospitalised have been under 50;
(2) average age for hospitalisation is 19;
(3) average age for those who've died is higher, at 37;
(4) about 75% of those who have died have had underlying health conditions ;
(5) there have been very few cases in people over 65, so they are very unlikely to be infected - but when they do get it, elderly people have a higher risk of complications and death.

So how mild is mild and what sort of symptoms do people have? Dr Schuchat said that most had a fever and respiratory symptoms, a cough, a cold, with some having diarrhoea. People may be miserable in bed for a few days, but the illness clears up on its own.

The US, unlike the UK, has restricted antivirals to those at most risk of complications, so comparatively few doses of Tamiflu have been handed out.

The CDC can't say yet how many people are asymptomatic - that is, the number of people that have such mild illness they don't even realise they've had swine flu - but with a million plus Americans thought to have had swine flu, it must be a pretty sizeable number.

A minority can have a much tougher time, according to Dr Schuchat:

"It's important for everyone to be aware of the virus, and especially for those with underlying health conditions, asthma, diabetes, chronic lung disease, and pregnant women: these people need to be especially concerned if they develop a fever and respiratory illness."

, and especially the morbidly obese (those with a Body Mass Index, or BMI, above 40) often have chronic lung disease, and that's why they were at risk of complications. Being obese on its own does not seem to be a risk factor.

To sum up: swine flu is here to stay. For the vast majority it is nothing to worry about. For a small minority, it can cause serious illness. It should neither be dismissed out of hand nor should it be a reason for panic.

Scientists must continue to monitor the virus to see whether it mutates or becomes more virulent or becomes resistant to antivirals; thankfully, there's no sign of those at present.

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A briefing by the chief medical officer for England Sir Liam Donaldson and the new Health Secretary Andy Burnham yielded some interesting new thinking on H1N1 swine flu.

Let's start with antivirals. At present, everyone in the UK who is suspected of having H1N1 swine flu is offered them. But the virus is proving so mild that it has got health officials wondering whether this really is a sensible policy.

The Department of Health, like global health bodies, was expecting the next pandemic to be a more aggressive virus with a higher mortality rate.

There are plenty of antivirals to go round - enough Tamiflu (and the lesser-known Relenza) for half the population, and eventually for eight in ten people in the UK. Sir Liam Donaldson said that he'd asked scientists to look into the issue. "People with seasonal flu don't get antivirals," he said. "Should we be treating only those who are at higher risk of complications?"

It would represent a big shift in policy on Tamiflu. Already, some of those offered the drug are turning it down because they don't see the point in taking it when they have only mild symptoms or are simply a close contact of someone infected, or because they want to avoid possible side-effects like nausea.

But before people say that the whole pandemic issue has been a lot of fuss over very little, a word of caution. Sir Liam pointed out that they were working on the basis of three potential scenarios for this autumn and winter:

(1) the virus is largely unchanged and remains mild;
(2) it changes and becomes more severe (bear in mind that all flu viruses mutate, which is why we need a new seasonal flu vaccine each winter);
(3) (and the least likely option, says Donaldson) it combines with another virus subtype and a new strain emerges.

If (2) or (3) occurs, then the pandemic would become more serious.

Another topic that came up was vaccines. Sir Liam said the government hoped to get the first doses of H1N1 vaccine in August.

By the end of the year, we were told, there might be 60 million doses, enough for about half the population, based on the assumption that each person would need two jabs.

Sir Liam said there was a "cookery book element" to vaccine production, which I took to mean that the yield and dosing strategy varied from year to year. As a result, we can't yet be sure when we will get all the vaccine. Another issue, not discussed, is that the UK is just one of many countries which has contracts for vaccine, and there will be pressure from all governments to get their doses first.

Another issue that the government must grapple with is who to vaccinate first.

Sir Liam said that they had to strike a balance between protecting people at higher risk and targeting the vacine to slow the spread of the virus. The latter could be done by vaccinating everyone in outbreak areas. But Sir Liam indicated it was more likely that at-risk groups would be protected first. Nothing was said about front-line health workers, but I would expect this group to be among the first to be immunised. Andy Burnham said that, as with all such issues, they would be "led by the science".

Mr Burnham pointed out that the vaccine contracts would eventually supply 130 million doses. But officials can't yet say when all the jabs will arrive. It's quite possible that millions of Britons will encounter the virus before they are offered a vaccine - it all depends on what happens this autumn.

But Sir Liam pointed out that the vaccine will be useful even after this autumn: "In all previous pandemics, excess mortality has occured for three years after the virus appeared".

Finally, how do you know what will happen if you, your child or a friend feels ill with suspected swine flu?

The answer is: it depends entirely on where you live.

In parts of London, the west Midlands and east Berkshire (all swine flu "hot spots"), there is a shift away from containment towards "outbreak management" because there are so many cases in the community. I will set out the three phases involved in managing the outbreak in the UK:

• Containment phase: this is still be used in many areas where there are few cases. Contacts of infected people are traced and offered antivirals, schools may be closed and all those suspected of infection are tested via nasal and throat swabs, to produce a laboratory diagnosis. In this phase, it is the Health Protection Agency that takes the lead.

• Outbreak management phase: this is the policy in hotspots. Only a small proportion of suspected cases will be swabbed (so that the HPA can keep tabs on the spread of the disease) and instead, GPs will do clinical diagnosis. Schools are unlikely to close. Contacts are not traced and Tamiflu might be restricted only to those with suspected infection. Areas will change to this policy once the virus is spreading widely in their community. Each area might adapt the policy to suit their local circumstances - "flexibility" is the buzzword.

• Treatment phase: this will be a UK-wide policy, according to Sir Liam. He suggested it would be triggered when there were "west Midlands-style outbreaks in five parts of the country". The NHS takes the lead instead of the HPA and it's treated a bit like a large outbreak of seasonal flu. But the aim would be to take pressure off GPs and to encourage people to use a telephone line to report symptoms. Those who are thought to have the virus will get a unique number which will allow a "flu friend" to collect antivirals from a collection point - which may not be a traditional pharmacy. The HPA willl keep tabs on the virus and check if it is changing or developing resistance to antivirals.

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The huge increase in cases of H1N1 swine flu in the west Midlands has led to a sudden rush of the "worried well" to casualty.

The , which runs three big hospitals, says it has had to set up sectioned-off areas in casualty to deal with people who fear they have the H1N1 virus.

At Heartlands Hospital in Birmingham, up to 100 extra people a day are turning up at casualty, which is something like a 25% increase as compared to usual.

The hospital is having to tie up medical staff to assess the influx of supposed swine flu cases. Anyone who does not have a fever - a temperature of over 38 degrees - plus two other symptoms (such as cough, headache or diarrhoea) is being sent home.

Many simply have a cough, a cold, or are feeling a bit "under the weather".

For a minority with obvious symptoms of the virus, the staff performs swab tests, and then sends those patients home as well. Dr Tony Bleetman, a consultant in the emergency department, says that if you do have the virus, you shouldn't be going to hospital, where you may spread the disease:

"Even if they have swine flu, it's mostly behaving like the common cold and we wouldn't expect people to come to hospital with that."

If you have concerns, the advice is to . But Dr Bleetman says that many of those turning up have done that:

"The problem is that significant numbers are being sent to us after consultation with NHS Direct and we think that NHS Direct are too quick to send people to hospital."

The problem began last week as the number of cases in the west Midlands began to soar. (as they phrase it) to stay away.

I've mentioned the problem of the worried-well before. It is a real concern of the WHO that the anxious should not clog up hospital emergency rooms during a pandemic. Imagine if what's happening in the west Midlands gets repeated at hospitals across the UK as the virus spreads.

What's interesting is that the worried well have not been a problem in Scotland, where there was a peak in swine flu cases a few weeks ago. The which covers a region of two dozen hospitals, told me that they had not noticed any sudden influx at casualty. Bear in mind that Scotland has had the only death from swine flu.

Maybe the public health messages have been more effective there. Or perhaps there are simply more "worried well" (or, as harsher observers term them, ) south of the border. Discuss.

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A sharp increase in the global number of cases and deaths can been seen in . The total now stands at 52,160 laboratory-confirmed cases including 231 deaths in around 100 countries and territories.

Beware any attempt to derive a "death rate" from such figures (which, by my reckoning, would come out as four deaths in every 1,000 people infected). As has been repeatedly pointed out, the vast majority of cases go unrecorded, so the figure of 52,160 is a huge underestimate of the actual numbers. Work is clearly needed to get a more accurate figure for the mortality and morbidity (ill-health) associated with the virus.

England has also seen a series of big daily increases in lab-confirmed cases in recent days. There were ; the total number in England has doubled in just five days, with the West Midlands accounting for half of all infections. The vast majority of those infected have experienced mild flu-like symptoms and fully recovered. There have been no deaths in England and one in Scotland.

The graphs below will show you the figures for the six countries worldwide with the biggest case-loads, in descending order: United States, Mexico, Canada, Chile, UK, Australia.

USA cases

Mexico cases

Canada cases

Chile cases

UK cases

Australia cases

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has held another useful briefing on the progress of H1N1 swine flu in the United States. Since the US is the global centre of the outbreak with far more cases than anywhere else, though fewer deaths than in Mexico, we can learn from that experience about how the virus is behaving now and what may happen in the coming months.

Dr Daniel Jernigan, Deputy Director of the Influenza Division at the Centers for Disease Control and Prevention made :

"The U.S. will likely continue to see influenza activity through the summer, and at this point we're anticipating that we will see the novel H1N1 continue with activity probably all the way into our flu season in the fall and winter. The amount of activity we expect to be low, and then pick up later. In terms of the numbers of infections that have been laboratory confirmed as H1N1, there are now more than 17,800 of those in the United States, including around 1,600 that have been hospitalized and 44 that have died. As we have been saying all along, these numbers are likely an underestimate of the number of cases that are out there. There are some surveys that indicate that the amount of disease in the areas that are having activity with H1N1 is perhaps around 7% of the population reporting symptoms due to influenza-like illness. The virus continues to impact mostly younger people. So far it is not causing significant illness and death in the elderly like we would see with seasonal influenza. And the symptoms that are being reported are consistent with influenza, that being predominantly fever, cough, some shortness of breath, fatigue and chills. There is some vomiting and diarrhea that have been associated with cases of this infection. Everyone needs to be alert to the symptoms of the illness, and especially if you have underlying conditions, such as asthma, diabetes and heart disease."

"Jon Cohen: Dr. Jernigan, you said there might be as many as 100,000 Americans infected. With the finding that 7% had influenza-like illness in affected communities, that extrapolates to 20 million Americans. Could you give an estimate that's more up to date than the 100,000?
"Dan Jernigan: "Well, the 100,000, as you know, is a rough generalization to try to give a sense of the magnitude of infections that might be there relative to the numbers of laboratory confirmed that we actually had. And so as you can see, in some areas, where there have been a lot of transmissions, like New York City, they're finding maybe around 7% of the community was infected, or had influenza-like illness. There's some other parts of the U.S. where some of our preliminary data suggests the same thing. I think it would be inaccurate to try and take an attack rate of 7% or an area that's highly affected and apply that to the U.S. population. Because as we all know, the amount of disease is different in different parts of the U.S. And so clearly there are hundreds of thousands of cases that have occurred in the U.S. We are working to get a very good estimate of that. But at this point, it would be incorrect to take that percent and apply it to the U.S."

So the CDC clearly doesn't yet have a clear idea of the true number of cases in the US beyond saying that there have clearly been hundreds of thousands. One final quote from Dr Jernigan on those who are most at risk of complications responding to a question from Emma Hitt at MedScape:

"Dan Jernigan: Your question is, what numbers of individuals that are hospitalized have underlying diseases, and about 70% have some kind of underlying disease. The most predominant of that is asthma. The second being diabetes. Immunocompromised status, either through cancer chemotherapy or other compromising conditions is about 13%. And chronic underlying heart disease. The things that we see normally as underlying diseases that are associated with increased influenza risk are the same that we're seeing with H1N1."

Cases seem to be declining in New York, one of the worst affected areas. For those interested in the impact on health and hospitalisations in the city, there is more detail available from the

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A further sign of the spread of H1N1 swine flu in the UK has come with news that many patients in Birmingham who exhibit symptoms will no longer have laboratory tests to confirm the disease.

Instead, doctors will rely on clinical diagnosis (in other words, a simple physical examination). The west Midlands has just over half of all the confirmed cases of swine flu in England.

Furthermore, in the areas of significant community spread in Birmingham, antivirals will be restricted to high risk and immediate contacts and household members, rather than everyone that an infected person may have been in contact with.

This is exactly what was announced last week in Scotland regarding the outbreaks in Glasgow and Paisley.

It's entirely unsurprising, and a common-sense response once there are significant levels of transmission.

One hundred and ten further patients under investigation in England were confirmed as having swine flu through laboratory testing today, together with 22 in Scotland. This brings the official total since April to 1,784.

The real figure will be significantly higher. The vast majority have had a mild illness with no complications. There are currently six people in hospital in Scotland who have the virus.

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Your eyes may glaze over at the thought of graphs. But if, like me, you find them useful, then read on. I'm indebted to my colleague Kate Merriam from 91Èȱ¬ Research for collating these figures from the World Health Organization website, from the HPA in England and from Health Protection in Scotland.

Before the numbers, here are some points to bear in mind.

First, health officials have been charting the spread of H1N1 swine flu for around seven weeks now. Most of the cases mentioned will now be virus-free and healthy.

Second, the WHO figures lag behind the real total by a couple of days. For example, the death toll for the US is quite a bit below the current figures from the CDC. But the WHO figures, while out of date, are reliable.

Third, all the graphs vastly underestimate the actual number of cases. The CDC has said that perhaps 19 out of 20 cases go unrecorded, and the state of Victoria in Australia has stopped laboratory testing of uncomplex community cases. Given those caveats, I think the figures are useful.

Global H1N1 swine flu cases

First, . As of 1700 BST on 15 June 2009, 76 countries have officially reported 35,928 cases of influenza A(H1N1) infection, including 163 deaths.

Now let's look at some individual countries.

UK cases

First, the UK. Figures are from and Health Protection Scotland.

The number of confirmed cases in the UK now stands at 1,562. There has been one death, that of 38-year-old Jacqueline Fleming, a mother who gave birth prematurely after contracting the virus. Yesterday, . He did not have the virus.

A further 141 patients were confirmed with H1N1 swine flu in England today (I think this is a record number for one day in England), bringing the total to 952 cases.

Of the new cases in England, 124 appeared in the west Midlands, where 512 people have been affected by the virus. There was one new case in Northern Ireland, bringing the total to nine.

Three cases have been recorded in Wales. Health Protection Scotland said there had been 10 new laboratory-confirmed cases today, taking the total to 508, with 414 possible cases under investigation.

USA cases

17,855 cases and 45 deaths at 15 June. This represents a rise of 4,638 cases and 18 deaths since the last report on 12 June.

Mexico cases

6,241 cases and 108 deaths with no cases reported in the last three days. This can surely only mean that the figures were not forthcoming or that the authorities are not testing in the community. I will try to investigate further.

Yesterday, the said that the US Centers for Disease Control and Prevention (CDC) had lifted the recommendation that American citizens avoid all non-essential travel to Mexico.

Australia cases

1,823 cases and no deaths, with 221 new cases.

China cases

318 cases and no deaths, with 100 new cases.

Japan cases

605 cases and no deaths, with 56 new cases.

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I'm going to talk here about the risks associated with getting H1N1 swine flu during pregnancy. Although it's not been officially confirmed, it's understood that the first person with H1N1 swine flu to die in Britain was a 38-year-old mother who had given birth prematurely.

The patient, who has not yet been named, was admitted to hospital with swine flu and . The child was born at 29 weeks gestation.

Few details have yet been confirmed by the Scottish authorities; they have so far said only that the patient had "underlying health conditions". Her death is very sad news, and everyone's thoughts must be with her family, friends and the medical staff who cared for her.

Before I go on to discuss the elevated risks of swine flu associated with pregnancy, it's important to stress, as I do repeatedly, that the vast majority of people who contract this virus have a mild disease which lasts a few days. Many will have no symptoms at all.

The official figure for the UK is 1,261 cases and this is the first death. But there will have been hundreds - maybe many thousands - of cases which have gone unrecorded. So instead of being one death in 1,261 cases, it is undoubtedly a lot less than that.

With around 700,000 babies born in the UK each year, I know that many women and their partners will be concerned. So please be reassured that the vast majority of pregnant women who get infected will be okay, as will their unborn children.

Having put all those caveats in place, it is true that pregnancy is a risk factor for swine flu.

The director general of the World Health Organization, Margaret Chan, had this to say about pregnancy last week, :

"Without question, pregnant women are at increased risk of complications. This heightened risk takes on added importance for a virus, like this one, that preferentially infects younger age groups."

When a vaccine for H1N1 swine flu becomes available in the autumn, pregnant women may well be among the first "at risk" groups offered the jab.

What about antiviral drugs and pregnancy? During pregnancy, the concern with any drug is that it may pass through the placenta and affect the baby. There is a risk factor especially during the first trimester.

Oseltamivir (currently best known as the brand name Tamiflu) is not usually recommended for pregnant women because the are unknown. But the lesser-known inhaled drug Relenza (a brand name for zanamivir) can be prescribed on medical advice, according to the Department of Health.

:

"An expert group reviewed the risk of antiviral treatment in pregnancy, which is extremely small - much smaller than the risk posed by the symptoms of swine flu."

There are more details on pregnancy and swine flu on .

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The death of a woman suffering from H1N1 swine flu in Scotland is a sad reminder that this is not always a mild infection. This is not only the first confirmed death in Britain, but the first outside of the Americas.

But it is not a signal that the virus is getting more virulent or that people are at any greater threat. The vast majority of the 1,200-plus people who have had the virus in the UK have experienced mild symptoms and then fully recovered.

Throughout the world, swine flu does present a slightly higher risk to those with existing respiratory illness, asthma, cardiovascular disease and obesity. It's worth remembering that seasonal flu kills several thousand people in the UK each winter. The difference with H1N1 swine flu is that the virus is almost exclusively targeting people under 65.

It is likely that cases in the northern hemisphere may tail off in the summer months, with a much bigger outbreak in the autumn. The virus can't be stopped altogether, but everyone can help to slow its spread by observing simple hygiene measures, and by staying home if they get the virus.

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Do you want to avoid catching H1N1 swine flu?

You could find a remote, uninhabited island until a vaccine is created. I think that's going a bit far. But the best defence is age.

So far, the over-65s has been the group least likely to catch the infection. This has led to me receiving cheery comments from retired people saying that it's the first time in some while that they've felt glad to be old.

So why aren't they falling ill? The likeliest explanation is that they have built up immunity over years of exposure to other H1N1 flu viruses. That might also help to explain why most other people get a mild infection.

But I'm still puzzled as to why 30- to 50-year-olds are suffering a disproportionate amount of severe illness. In fact, I'm a bit puzzled as to exactly which age groups - under the age of 65 - are most at risk of severe illness.

In , Margaret Chan, the WHO director-general, had this to say:

"We know that the novel H1N1 virus preferentially infects younger people. In nearly all areas with large and sustained outbreaks, the majority of cases have occurred in people under the age of 25 years.
"In some of these countries, around 2% of cases have developed severe illness, often with very rapid progression to life-threatening pneumonia. Most cases of severe and fatal infections have been in adults between the ages of 30 and 50 years. This pattern is significantly different from that seen during epidemics of seasonal influenza, when most deaths occur in frail elderly people. Many, though not all, severe cases have occurred in people with underlying chronic conditions.
"Based on limited, preliminary data, conditions most frequently seen include respiratory diseases, notably asthma, cardiovascular disease, diabetes, autoimmune disorders, and obesity.
"At the same time, it is important to note that around one third to half of the severe and fatal infections are occurring in previously healthy young and middle-aged people. Without question, pregnant women are at increased risk of complications. This heightened risk takes on added importance for a virus, like this one, that preferentially infects younger age groups."

This was very similar - up to a point - to in Atlanta. You'll notice the same emphasis on younger age groups, pregnant women and those with underlying health problems. This is what Dr Anne Schuchat had to say about the US experience of H1N1 swine flu:

"It is a very new virus. 57% of the cases that we're having reported to us occur in people five to 24 years of age, and 41% of the hospitalisations are in that same age group - the older children and young adults. But I also want to tell you about the rates, the cases per 100,000 population, and let you know that the highest rates of hospitalization are actually in children under five. And the next highest rates are in those people 5 to 24. So it looks like this is a virus that's disproportionately affecting younger people but there are still lots of infections and hospitalizations in older persons.
"According to the US statistics, 71% of the hospitalized patients have occurred in people who have an underlying condition - respiratory illness like asthma or conic obstructive pulmonary disease, immune deficiencies, and so forth. As we have noted, there's been a disproportionate amount of pregnant women among those who have had infection."

Did you spot the difference? Dr Schuchat made no direct mention of the 30-50 age group, although she did mention that there were lots of people over 24 who are taken to hospital. If the 30-50 year group is especially at risk, it would be good to know. I'm still just in that age group myself, so maybe it's self-interest at work here. No doubt all will become clearer in the months ahead. When it does, I will let you know.

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Flu pandemics are an .

There were three in the 20th Century. The worst, , killed perhaps 50 to 100 million people - but that was before the antibiotic era.

The pandemics of and killed one to two million. Even that sounds alarming, but bear in mind that normal seasonal flu contributes to up half a million deaths per year.

And H1N1 flu is currently so mild that, in terms of deaths, it might not be much worse than a bad normal winter of flu.

But it is different in the groups it targets. Very few elderly people are catching H1N1 flu, probably because they have immunity due to exposure to similar flu viruses.

Instead, the peak groups are children and young adults aged 5-24, followed by children under five, and then adults under 50. Most of those who fall seriously ill, with complications like pneumonia, have underlying health problems.

But of the 140 or so deaths so far worldwide, about half have been in previously-healthy people. That is what prompted the World Health Organization to .

People will want to know when they are likely to be exposed to H1N1. That's impossible to say with any accuracy, but the summer months may suppress the virus somewhat in Britain, and it may be the late autumn or beyond before we see a full-scale epidemic in every community.

suggest that perhaps a third of the population could get infected, causing huge rates of absenteeism from work, and extra pressure on the health service.

There is concern that the virus might mutate in the southern hemisphere over its winter and become more virulent, but there's no sign of that yet.

A pandemic vaccine is in early development; it will be autumn before the first doses are ready; they will be earmarked for front-line health workers and those with health problems.

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Hours before the is , I've been seeking expert comment from two of the worst affected countries outside North America - Scotland and Australia.

Along with Chile and Japan, these are the countries which are forcing the move to Phase 6, a global epidemic or pandemic.

Dr Ian Barr is the Deputy Director of the .

He's based in Melbourne, which is the centre of the flu outbreak there.

The state of Victoria has had more than 1,000 confirmed cases of swine flu and Dr Barr said that the government was now changing the way it managed the outbreak.

"If someone is ill then we will continue to ask that they stay at home and don't go out and risk infecting anyone. But there won't be a recommendation for quarantining whole families as has happened.
"Unless someone falls quite ill they won't be given antiviral treatment like Tamiflu and we won't trace their contacts. We won't close schools if there's a single case, so it's a much more relaxed approach than we've had prior to this phase."

But Dr Barr said that the virus was not causing serious problems:

"We've had just a handful of cases admitted to hospital and no deaths.
"There've been very mild symptoms among the 1,000 laboratory confirmed cases and probably thousands more that have not been tested."

With the southern hemisphere moving into its peak winter flu season, it will be vital to keep a close watch on what happens there in the months ahead.

Scotland, by contrast, is heading into summer. That did not stop , the highest number for a single day. It takes the total to 311.

Ten people are in hospital. Dr Harry Burns, the , said that there was no doubt that they were seeing community transmission well beyond the confirmed cases.

"The last figures I saw there were between 30 and 40 cases where there was no known source for the infection - it did not seem to be travel-related or connected to a particular outbreak. But sometimes people don't always remember their contacts".

Dr Burns said that there was also no doubt that there were plenty of cases going untested and unmeasured, just as was happening in other countries.

I asked him whether it was time for a change in approach as is happening in Australia, with fewer school closures and so on.

"We are getting close to a change in strategy, but quite how and when it is rolled out we can't say yet. We will continue to take scientific advice.
"If you have a new travel-related case in a rural part of Scotland where there have been no cases, then you may look for contacts. That might be less so in other areas where there have been lots of cases."

He has no doubt that the virus is here to stay and he hoped that it would remain a largely mild infection.

"But it's worth preparing for the worst. The nightmare scenario a few years ago was that H5N1 avian flu would reassort with a human flu virus in pigs.
"If H1N1 reassorted with H5N1, it would be important to have some initial protection against the H1N1 strain. That's why it's worth creating a vaccine."

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So it's now just a question of timing. Within a day or so the World Health Organisation will officially declare a pandemic of H1N1 swine flu.

The move to pandemic Phase 6 will be official confirmation that the H1N1 virus is here to stay and that it will continue to spread globally. It must be hoped that the world does not over-react.

It will probably be months before most of us come into contact with the virus, and when we do, the vast majority will experience mild flu symptoms. It is not an indication that the virus is becoming more virulent. If those messages can be effectively communicated to the public, it could prevent a lot of unnecessary alarm.

A key decision concerns vaccines. Several manufacturers now have an H1N1 seed virus strain, and will be doing safety and efficacy testing in the coming months. We don't know how well the virus will grow or how many doses people will need to be protected.

Given the moderate nature of H1N1 it would be inconceivable for the WHO to ask manufacturers to switch completely from production of seasonal flu to a pandemic vaccine.

More likely is that companies will try to do a bit of both. Several countries, including the UK, have contracts to provide enough doses to immunise their entire populations. But despite upscaling in production in recent years, there won't be enough jabs to go round globally.

The first bulk doses might be ready in the late autumn and would be earmarked for frontline emergency staff and those with chronic respiratory problems. It's possible that by the time an H1N1 vaccine is ready, the virus will already be spreading rapidly in the northern hemisphere. We will learn a lot from what happens in Australia and other southern hemisphere countries in the months ahead.

So are we over-reacting to swine flu? I don't believe so. Even a pandemic of mostly mild illness will still cause huge disruption to business and society during its peak because it mostly affects those of working and school age.

Although the vast majority of those infected get mild symptoms, a few get seriously ill. The WHO estimates that about half the 140 deaths so far have been in young people who were previously healthy.

We must also watch out for genetic reassortment - or drift - in the DNA of the virus which might make it more virulent in future. There's no sign of that yet but it's another reason why we should all take the pandemic seriously, without the need for panic.

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When is a pandemic not a pandemic?

When the World Health Organization says so. With the virus spreading in Australia, where there's been a four-fold increase in cases in a week, it might seem surprising that global health officials have not yet moved from the current Phase 5 to 6, which would mean that a pandemic had been declared.

Predictions are a mug's game - but, on 91Èȱ¬ TV and radio this evening, I stuck my neck out and said that a pandemic declaration was likely within days, or possibly weeks at the outside.

The reason for this was that listening to the WHO's assistant director general Dr Keiji Fukuda in the weekly media briefing, it seemed to me that the WHO was holding back from declaring a pandemic for political reasons.

I'm not suggesting anything underhand, but simply that member states and scientists have advised the WHO that it must prepare the ground before making the move to Level 6. The WHO can't ignore the surge in cases in Australia, and, to a lesser extent, the leap in cases in the UK and Chile.

Dr Fukuda said that he feared "a blossoming of anxiety" - in other words, panic - if they suddenly declare a pandemic. It's true that the word "pandemic" sounds scary. But it simply means a global epidemic of an infectious disease.

It is not a signal that the virus is getting more virulent; it has nothing to do with severity; rather, it is a measure of geographical spread. And we must remember that the vast majority of people who get H1N1 swine flu have a mild illness.

Dr Fukuda said that it was fair to say that we are "really getting close" to declaring a pandemic, but that the WHO wanted to avoid or reduce the sort adverse actions that had happened when it last raised the threat level, such as the culling of pigs, unnecessary concerns over pork, trade embargoes, travel restrictions and concerns about travellers from certain areas.

"These are the kinds of potential adverse effects you can have if you go out without making sure that people understand the situation as well as possible.
"In earlier pandemics, we have often seen that people who are worried, but not particularly sick, have over-run hospitals and led to a dsyfunction in the health system because so many are going to emergency rooms, adversely affecting people who really require emergency care. We'd like to minimise the risks of that."

Governments, too, have a big role to play, ensuring that their pandemic plans are in place. And businesses must prepare for the coming of a virus which, even if it is mild, will cause huge numbers of absences from work.

Remember, though, that when a pandemic is declared, it won't make any difference to most of us. Different countries will experience local epidemics at different times. What matters is when H1N1 begins to spread rapidly within your community, way beyond schools and unrelated to travel.

Only then might the virus make a tangible difference to your daily life.

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Two experts on infectious disease in Australia say a flu pandemic has effectively already started because of the widespread number of cases there.
, professor of Child Health at the University of Sydney in New South Wales, urged the World Health Organisation to take action regarding a shift from the current alert phase 5 to the top level, phase 6: "The WHO can't keep scratching their heads, they have to make a decision," he said.

Professor Booy, who works at the Children's Hospital, Westmead, said the H1N1 virus was "unstoppable" and would continue to spread around the world. He expressed surprise that the WHO had not already declared a pandemic - a global epidemic of a new flu strain - because the H1N1 virus "fulfilled the criteria of community spread".

As yesterday's post made clear, the WHO has said once we have "community level outbreaks" in another region outside the Americas, then a pandemic will be declared. This means that the virus must be spreading widely, beyond schools and unrelated to travel.

Professor Booy said his neighbouring state of Victoria now had so many cases they would no longer be testing people with flu symptoms in the community, but rather limiting the test to those who needed hospital treatment. "We have community transmission in Victoria," he said.

Victoria has by far the bulk of Australia's swine flu cases. The Australian government said that of , 1,011 had been reported in Victoria.

The number of cases in Australia have risen four-fold in a week. Professor Booy said this was unsurprising. "The cycle of infection is about two days. For every one person with the virus, another 1.5 people get infected, so that gets you to a four-fold rise in six to seven days".

Professor Booy said thankfully the virus was causing mostly mild symptoms. "We have had some hospitalisations, and one person in intensive care, but all are doing well," he said. Fewer than 10 of the flu cases nationwide have required hospital admission. There have been no deaths.

Raina MacIntyre, professor of Infectious Diseases Epidemiology at the , said according to the , "we are in Phase 6; technically we are there already."

But she added, "it's just a guideline, and when the definitions were devised they didn't factor in severity. I think the WHO approach is reasonable given that there would be widespread economic, tourism and trade implications if a pandemic was declared".

Professor MacIntyre explained that the traditional thinking was that a pandemic would be caused by a new . This is one of the surface proteins on the flu virus, and is responsible for it binding to infected cells.

"We thought it would be caused by an H5 or an H9 type, rather than H1 which is not really new. When you look at the immunological response of the various age groups, people over 65 have a good level of protection, and only people under 18 have no immunity while many young adults have little immunity."

Professor Booy, who helped draw up Australia's pandemic flu plan said "We had many assumptions and one was that a new flu virus would cause high mortality caused by something really novel. The H1 gene has been with us for centuries."

But he warned that the virus could mutate or "drift" in the coming months. "We already know of cases where people have got double infections - both H1N1 and seasonal flu - and that's what you need for viruses to reassort."

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Apologies for constantly updating the figures, but I feel it's necessary at the moment: first, because the virus is continuing to spread; second, because of the dramatic surge in cases in the southern hemisphere.

The World Health Organization's latest figures show that 73 countries have officially reported 25,288 of influenza A(H1N1) infection (more commonly known as swine flu) including 139 deaths. It's worth comparing that with , when there were 17,410 cases in 62 countries and 115 deaths.

It's interesting to see the surge in cases over the past week in the southern hemisphere, which is entering its winter flu season. Australia's cases have leapt from 297 to 1051. Chile's cases have jumped from 250 to 411, with one death.

The UK has also seen a big increase. A week ago, the WHO reported 229 cases; today it had 557 (and remember that the WHO figures always lag behind national statistics by a few days).

If you are keeping track of what's happening in the UK, the more up-to-date figures are these:
• in Scotland, , bringing the total there to 232;
• in England, ;
• add four cases in Northern Ireland and two in Wales for a total of 664 - please forgive me if my arithmetic fails me at any point.

10 of the confirmed cases in Scotland are in hospital, including three in intensive care. Seven health care workers are now also among the confirmed cases. It's worth stressing yet again that the vast majority of people who have contracted swine flu have got mild symptoms.

So with 664 confirmed cases in the UK and more than a thousand in Australia, will a pandemic be declared by the WHO - and if so, when? :

"Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way."

You might argue that we are already there. But the WHO is looking for what it calls "sustained disease outbreaks" in the community. We have plenty of these in North America, and are .

, Director of Public Health Strategy at the Health Protecgtion Agency, we are not there yet: "The number of sporadic cases remains under twenty. These are confirmed cases of infection, but where there's no obvious link with travel or a known case".

Professor Kessel said that "we would need to have a significant number of people where you really don't know how they have got it, for it to be classified as sustained community transmission. We are getting closer to that, but are not there yet."

Finally, a quick update on anti-virals and potential side-effects, which some have asked me about. Professor Kessel said that Tamiflu has so far been used mostly for children in the UK because of the outbreaks in schools.

"There have been reports of some side-effects," he said. "The most common have been nausea and stomach pain, which is in line with the manufacturers' written warnings. At the HPA, we have reiterated the advice that it's best taken with food, as this seems to help."

Professor Kessel said that when anti-virals were prescribed, the HPA was very clear that this was advisory: "It's up to parents and their children together to decide whether or not to take Tamiflu - there is no obligation to comply."

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It's understandable that H1N1 swine flu has made fewer appearances on radio and television bulletins in recent weeks.

There was massive coverage when the virus first emerged and when the WHO raised the pandemic threat level to five, one short of six when a pandemic is declared.

But just because swine flu is not getting so much publicity, it does not mean it has gone away. Nor does it mean that the risk of a pandemic - a global epidemic of flu - has abated.

A few figures just released show how cases of swine flu continue to rise.

has confirmed 22 new cases. This includes two doctors at the Royal Alexandra Hospital in Paisley, who are thought to have caught it from patients being treated there. It brings the Scottish total to 141 including four patients who are in a critical but stable condition.

The has confirmed 27 new cases, bringing the total to 363. Northern Ireland and Wales have two cases each. It brings the UK total to 508.

In the United States the (CDC) has also put out new data which it says it will now update only weekly, on Fridays. It has 13,217 confirmed and probable cases and 27 deaths. At present the number of confirmed US cases is rising by about 1,000 per day.

The (WHO) released a new global update earlier today. Although it lags behind national statistics, it is still the gold standard for assessing the spread of H1N1 swine flu. It reports 21,940 cases in 69 countries including 125 deaths - 103 of these in Mexico.

Australia has 876 confirmed cases according to the WHO, up from 501 in two days. It now has the highest case-load outside North America. July and August will be the peak season for flu in Australia and there are signs that the virus is taking hold there very quickly.

If widespread community outbreaks are reported in Australia (or the United Kingdom, Chile or Japan in the coming weeks it will be a signal for the because the virus will have been shown to be spreading widely in two WHO regions of the world.

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Some interesting figures have emerged from the United States about the progress there of H1N1 swine flu.

Dr Anne Schuchat, gave a media update at a CDC press briefing.

The US has far more cases of H1N1 swine flu than anywhere else so they are beginning to get some more robust statistics which may help in our understanding of how this virus will affect the world. Dr Schuchat said there was evidence that flu activity was declining in the nation as a whole, with the start of the summer in North America.

Young children together with young and middle age adults were those most affected by H1N1 flu. Unlike seasonal flu, the virus seems to be sparing the elderly. Here are the statistics - the US has:

• 11,468 probable and confirmed cases of H1N1 swine flu (it's worth remembering that laboratory confirmed cases in the US represent only a small fraction of the real total)
• 770 people have been hospitalised
• 19 known fatalities
• 60% of all cases are among people aged 5-24 years
• 42% hospitalisations are among people aged 5-24 years
• Next highest group are children under 5
• Very low rates of cases and hospitalisations in people over 65

Dr Schuchat said that the CDC had provided several manufacturers with candidate vaccine virus strains. This will enable them to produce pilot lots of vaccine which can be tested for safety and efficacy. That will probably take a couple of months. At that point, the WHO and CDC will have to make the difficult decision about whether to ask manufacturers to bulk produce an H1N1 pandemic vaccine.

It's a difficult call because it would mean reducing the amount of seasonal flu vaccine production. Given that manufacturers are mid-way through the production of seasonal flu vaccine for the northern hemisphere this autumn, those stocks are unlikely to be affected. It is next year's immunisation in the southern hemisphere which would probably feel the first impact of any switch to pandemic flu vaccine production.

Dr Schuchat pointed out that seasonal flu caused around 200,000 hospitalisations in the US each year and about 36,000 deaths, so this was a disease they took very seriously. Worst affected are people over 65. She said the CDC would be recommending that the usual at-risk groups get immunised.

In the US this includes children aged 6 months to 18 years (a group not targeted in the UK), pregnant women, the elderly, those with serious health problems, and anyone who wants to reduce their risk of getting flu. I think it's a safe prediction that there will be a record uptake for the jab later this year.

So no decision has been made yet about whether to push the button on creating a mass stockpile of H1N1 vaccine in the US, or indeed the world. Dr Schuchat said they would await the outcome of test vaccine studies and carefully monitor the epidemiology of the virus. A decision, she said, would be made in the early autumn.

One encouraging fact is that tests of virus samples from around the world have not shown any variations; in other words, it doesn't look like there has been any mutation or drift in its genetic structure.

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How many people in the UK have swine flu? Do you want the official or the unofficial figure?

The number of laboratory-confirmed cases stood last night at 404. But there are undoubtedly some cases which have gone undetected. How many?

, a virologist at Queen Mary School of Medicine, University of London, has come up with a figure. Speaking this morning on 5 Live Breakfast, he speculated that there could be 20,000 infected people in the UK.

His theory goes that most of them have had such mild illness, it's gone undetected. I spoke to him afterwards and he stressed that this is a pure "guesstimate" rather than a scientific analysis of the figures. He stressed that the number was not meant to be alarming - and that quite the contrary, it shows that the virus causes mild symptoms in the vast majority of cases.

, Director of Public Health Strategy at the Health Protection Agency agreed that there are some undetected cases out there, but he didn't think that it was tens of thousands. He said that the UK had among the best flu surveillance systems in the world and doubted there could be that many cases.

That may leave you none the wiser. We may get a better idea by looking at what's happening in the United States.

There, the says that there have now been 11,054 confirmed and probable cases. But it has also repeatedly stated that possibly 19 out of 20 cases are going undetected. As I said in a post on Tuesday, this could mean that there are 200,000 or more people in the United States who have been infected.

So can you simply multiply the current official UK figure of 404 by 20, giving us around 8,000 cases here? It's quite a lot less than Professor Oxford's guesstimate, though still a lot.

But there are two differences I can think of between the UK and the US which may make that figure lower.

First, the virus is not as well established here as it is in North America. We are seeing cases pop up out of the blue, but most are linked to current outbreaks.

Second, the UK does have a very well organised flu surveillance service, one of the features of our GP network set within a national health service. Contrast that with the fragmented healthcare on offer in the US and it's little wonder that surveillance here is likely to be better.

All that probably means that fewer cases are going undetected here than in the US. Whether it's a few hundred or many thousands though, it's impossible to say.

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A nurse in Scotland has become the first health worker in the UK to catch swine flu.

The 26-year-old, who works at a Glasgow hospital, had been treating a patient who is now in intensive care with the virus. The details were . The nurse is now recovering at home.

There are now four people, critical but stable with swine flu, in hospitals in Glasgow and Paisley. A 23-year-old woman from Paisley was admitted today. Initially, it was thought that she had no underlying health problems, but Greater Glasgow and Clyde Health Board later ascertained that this is not the case.

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It was only a matter of time before Africa recorded its first case of H1N1 swine flu.

that a 12-year-old girl who'd travelled from the United States has been confirmed as Egypt's first case of swine flu. A government statement said that no other passengers on the flight showed signs of infection.

Egypt has also had sporadic cases of H5N1 avian influenza, .

Of the 78 cases of H5N1 reported, 27 have been fatal. Thankfully, H5N1 is very hard to catch and almost always requires direct contact with infected poultry. It is not an infectious human disease like H1N1. What the world is most anxious to avoid is the two viruses mixing.

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I've just finished listening to the now-weekly press briefing on H1N1 swine flu given by the in Geneva and here are some of the main points.

Dr Keiji Fukuda, WHO's Assistant Director-General, said that the virus had now reached 64 countries with 18,965 laboratory-confirmed cases and 117 deaths.

"We are getting closer to phase six," said Dr Fukuda, which would mean that a pandemic had occurred. He divided the global outbreak into three types:

• countries in North America where virus spread is advanced - Mexico, the United States and Canada;
• the group of countries - which he described as being "in transition", some in Europe, some in Asia, also Australia - where a larger number of cases is occurring, many linked to institutions;
• countries where there is no real evidence of spread into communities and cases are largely travel-related.

Dr Fukuda said that the countries in transition are moving towards community-type spread and include the UK, Spain, Japan, Chile and Australia. "But we are still waiting for evidence of widespread community activity, so that's why we are not in phase six yet".

He went on to say that the WHO was choosing not to describe the outbreak as mild. "This infection can be fatal - in those who have underlying medical conditions, pregnant women and in some people who were otherwise healthy."

And he said that we don't know what will happen in the southern hemisphere in the coming months, or in the northern hemisphere later in the year. The severity of the outbreaks, he said, would vary from location to location, according to the vulnerability of populations and their preparedness.

I asked Dr Fukuda which age groups were most likely to catch the virus and to die from it. "The majority of people who have got infected are under 60 years of age, although some people over 60 have also got infected," he said.

"Those who have got severely ill - with complications such as severe pneumonia and those who have died - have tended to be younger to middle age adults aged 20-40 or so, but not exclusively."

That ties in with the pattern one might expect from a . Normal seasonal flu tends to hit the elderly most severely; in pandemics, it is often young adults who are worst affected.

Also today, . A 45-year-old man and a 38-year-old woman are being treated in intensive care at the Royal Alexandra Hospital in Paisley. The Scottish government said that .

As yet, neither person has any known links to other cases, to travel or to each other. The man is believed to be the first person in Britain to be taken critically ill, suffering only from swine flu. The woman is said to have underlying health problems as does a third patient, a 38-year-old man, who was admitted to intensive care at a hospital in Glasgow last week.

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If you ask most people where you are most likely to catch H1N1 swine flu, my guess is they would answer, Mexico. That was the case initially, but has not been for some time.

Although most deaths from the virus have been in Mexico, it's the United States which has been the centre of the global outbreak for several weeks now.

The Centers for Disease Control and Prevention (CDC) CDC H1N1 Flu website has reported 10,053 probable or confirmed cases of swine flu, up from nearly 9,000 on Friday and 17 deaths. Furthermore, the virus has spread to all 50 states.

. If that is the case then it would suggest there could be 200,000 people in the US who have contracted the virus.

In one sense that would be worrying, as it would indicate that H1N1 is well and truly here to stay and that a pandemic is almost certain. But it would also confirm that the virus is causing mostly very mild illness, and mean that the death toll from a pandemic might be no worse than with seasonal flu.

Remember though that scientists are still learning about the virus and are unsure how any pandemic might

the global number of confirmed cases of H1N1 is 17,410 in 62 countries, including 115 deaths. Since then, Bulgaria and Luxembourg have confirmed their first cases of the disease.

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One of the UK's leading flu experts has predicted that a pandemic of swine flu is likely to strike Britain in the autumn. , an expert on virology at Queen Mary School of Medicine, University of London, says that children going back to school, universities reopening and people going back to work after the summer break would give swine flu the "opportunity" that it needs to spread.

Another fifteen cases of swine flu were , bringing the UK total to 244. One of the cases was in Wales and is believed to be the first there.

But Professor Oxford thinks that many cases are going undetected:

"Already, sporadic cases in the UK have been shown that are not linked with cases that have travelled. That does suggest that the virus is silently spreading around."

However, he said that people should behave as usual, as far as possible, if a pandemic strikes. "What we don't want is people stopping at home and not going to work, because then you have an economic problem on top of a pandemic," he said. "The best advice is to carry on as normal but to be sensible about it. "This includes a bit of social distancing and shielding people from coughs by coughing into the crux of your arm."

Professor Oxford said that in the next few months, global health officials will be keeping a close eye on what happens to the H1N1 swine flu virus in countries like Australia and South Africa. The southern hemisphere is entering its winter and the peak period for flu. On Friday, reported that Australia has had 147 confirmed cases; Argentina has had 37; and none so far in South Africa.

What happens in the southern hemisphere in the coming months will be a good indicator of how the virus will behave in Europe and North America later this year. There would be particular concern if H1N1 mutated substantially to become a more virulent illness. Thankfully, there are no signs of that yet.

The is an excellent resource for anyone wanting to know what experts are thinking about the spread of the virus there. The has lots of reliable specialist comments on flu and a host of other issues.

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