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The return of swine flu

Fergus Walsh | 16:50 UK time, Wednesday, 15 December 2010



It should be no surprise that swine flu is back. In recent days there has been a spate of headlines speaking of "shocked" doctors, alarmed by the return of "deadly" swine flu. What should we make of this, and should we be worried?

First off, the H1N1 virus, which sparked a pandemic last year, never really went away. Influenza is a largely seasonal phenomenon, with peaks every winter and very low background levels at other times. Flu pandemics are the exception, and as last year showed, they can begin in any season.

Anyone can get flu, at any age. For most, influenza causes an unpleasant but self-limiting illness which lasts several days. If you got a mild dose of flu last year then you may wonder what all the fuss is about. But for a small minority flu can be serious, even fatal. Last year, those under 65 were especially at risk from the complications of H1N1 and that pattern is continuing this winter.

The Health Protection Agency said last week that there have been 10 deaths due to H1N1 flu in the past three months. Most of those who died had underlying health conditions. The Royal College of GPs said today that there has been a "substantial increase" in all respiratory diagnoses in the past week, especially in the 5-14 and 15-44 age groups.

So swine flu is "out there", but so many people caught it last year that there is a reasonable level of immunity in many communities. The 10 recent fatalities can be compared with 474 confirmed swine flu deaths in the UK in the first 12 months of the virus circulating (up to mid-April 2010). It would be wrong to suggest that virus is somehow more deadly or more serious than previously. Around one in five of those who died from swine flu last year had no underlying medical problems, among them pregnant women and children.

In recent weeks several people have needed specialist emergency treatment due to lung failure, using machines which pump oxygen into the blood outside the body (ECMO). Pregnant women, and those with underlying health conditions are among those most vulnerable to the complications of H1N1.

It is worth stressing that flu is a vaccine-preventable illness. The Health Protection Agency has urged people in at-risk groups to get immunised. The seasonal flu vaccine is always trivalent - so it protects against the three most likely circulating strains of flu. This year the vaccine contains antigens against the influenza type A strains H1N1 and H3N2 and against flu B which mainly affects young children.

From this year all pregnant women are being offered the trivalent seasonal flu jab (last year they were offered the monovalent (single antigen) H1N1 vaccine due to the pandemic). Other groups offered the flu jab are those aged 65 and over, people with breathing problems, heart, kidney or liver disease, diabetes and those who have a suppressed immune system. NHS Choices has a full list of those eligible for a free flu jab.

So far this flu season two thirds of people in England over 65 have been immunised. Four in ten people under 65 in an at-risk group have received the jab. Flu viruses alter every year, which is why people are offered an annual jab. So if you got a flu vaccine last year (seasonal or pandemic), it does not mean you are definitely protected now.

By the way, you may have missed it, but the swine flu pandemic is over. The term "pandemic" is a largely bureaucratic one in relation to influenza. It was in August that the World Health Organization declared the pandemic over because the H1N1 virus had "largely run its course".

This was not meant to indicate that the virus was on the way out, rather, that it was now acting alongside other flu strains.

The WHO director general Margaret Chan gave this warning in relation to swine flu:

"It is likely that the virus will continue to cause serious disease in younger age groups, at least in the immediate post-pandemic period. Groups identified during the pandemic as at higher risk of severe or fatal illness will probably remain at heightened risk, though hopefully the number of such cases will diminish.

In addition, a small proportion of people infected during the pandemic, including young and healthy people, developed a severe form of primary viral pneumonia that is not typically seen during seasonal epidemics and is especially difficult and demanding to treat. It is not known whether this pattern will change during the post-pandemic period, further emphasising the need for vigilance."

So swine flu is back and we can expect H1N1 to be a dominant strain for many years, until the next flu pandemic arises.


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