Youngest likeliest to be infected, swine flu study confirms

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Youngest likeliest to be infected, swine flu study confirms

Wed Nov 11, 7:10 pm ET

PARIS (AFP) – New data from Mexico, the epicentre of the swine flu pandemic, has

confirmed that young people are most at risk of catching the A(H1N1) virus but

elderly patients are most at risk of dying from it.

The study bolsters the belief that the pathogen is not as virulent as first

feared but also stresses the need for caution, as a mutation into a more lethal

form cannot be ruled out.

Epidemiologists led by Victor Borja-Aburto of the Mexican Institute for Social

Security looked at data for 63,479 people who had been treated for flu-like

symptoms in public clinics from the start of the scare in April until the end of

July.

Of the 6,945 cases confirmed by tests as H1N1, 56 percent occurred among people

between 10 and 39 years, an age group with a high risk of contact through social

interaction.

There were far fewer cases among older patients, which suggests that people in

this age group were exposed in the past to a cousin to swine flu and may have

gained some immunity, the author say.

But when analysed for mortality, a " J-shaped curve " revealed a preponderance of

deaths among the elderly.

Among patients aged between 60 and 69, the death rate was 5.7 percent, compared

with only 0.9 percent among patients aged between 20 and 29 years.

The study adds to several previous analyses which suggest vaccination against

seasonal flu provides a partial shield.

It also strengthens warnings that people with chronic underlying disease are

especially vulnerable. Individuals in this category increased their risk of

death sixfold.

As of November, 1, more than 199 countries had reported lab-confirmed cases of

swine flu, according to a toll published by the World Health Organisation (WHO)

last Friday. There have been more than 482,300 notified cases and at least 6,071

deaths.

But the real number of swine flu infections is likely to be very much higher as

many countries have stopped counting individual cases, says the WHO.

In addition, the count does not include people who have only mild symptoms -- or

no symptoms at all -- and thus do not bother seeing a doctor.

The mortality rate from swine flu has been variously estimated at between 0.2

and 1.23 percent, according to the country or region or social group that is

analysed.

At its lower range, this estimate is akin to the death toll from ordinary,

so-called seasonal flu, of around 0.1 percent.

But even the highest figure is still only half of that for the 1918 Spanish flu,

where the mortality rate is estimated to have been at least 2.5 percent. Tens of

millions of people were killed in that event.

" Some researchers believe, with the information available up to now, that the

present H1N1 influenza virus will not cause a pandemic on the scale of those

during the 20th century, " said the new study, published online on Thursday by

The Lancet.

" This pandemic might not be the one we expected; however, the virus is evolving

and the threat continues. "

http://news./s/afp/20091112/hl_afp/healthflu_20091112001018