LIKE THE SPANISH FLU, AVIAN INFLUENZA KILLS MORE YOUNG THAN OLD

HUMAN FATALITIES HAVE TRIPLED IN 2006

The World Health Organisation has studied the detail of more than 200 human infections of avian influenzea and uncovered a remarkable link with the fatalities of the 1919 Spanish Flu pandemic.

H5N1 has a higher human mortality rate in the young than the middle aged or elderly. Also, deaths from avian influenza tend to surge during the winter months. Even if the virus doesn't mutate into a form more likely to spread one human to another, a rise in human deaths is still expected this year.

A WHO report, written up by the New York Times here, claims the risk of the virus growing in strength and its ability to infect more and more humans remains high this year, "because of the widespread distribution of the H5N1 virus in poultry and the continued exposure of humans."

The median age of victims with confirmed cases was 20 years, the report said. The highest death rate — 73 percent — was among patients ages 10 to 19, while the overall fatality rate was 56 percent. This pattern has been noted before, but the new analysis takes in more cases; the typical age is drifting downward.

A high death rate among young adults echoes the pattern found in the 1918-1919 epidemic, said Dr. Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

Scientists contend that year's H1N1 virus was also an avian flu that mutated until it spread easily among humans; although it was fatal to only about 2 percent of those who caught it, that was enough to kill between 40 million and 100 million people worldwide.

Unpublished W.H.O. data from blood sampling around recent outbreaks, Dr. Osterholm noted, shows that few people carry antibodies to the virus, so there is not a huge pool of survivors of mild avian flu.

Evidence suggests that many young people in 1918 and quite a few in this outbreak are killed by a "cytokine storm" — the body's own immune reaction, which floods the lungs with fluid. Young adults generally have strong immune systems.

The W.H.O. is tracking changes in the virus, trying to predict if it will mutate into a more infectious form and hoping to build vaccines against it in time to head off a pandemic.

Fatalities from the virus have almost tripled this year compared with last year.

The typical avian flu victim is sick enough to be hospitalized four days after falling ill, and dies five days later, the report said. People over 50 have the lowest death rate, but it is still 18 percent, which is a huge impact compared with seasonal flu.

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