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Bird flu kills younger people, copying 1918 pandemic, WHO says

Bird flu tends to kill younger people, mirroring the pattern of the 1918 Spanish flu pandemic, and the risk of the virus causing a worldwide outbreak in humans remains high, a World Health Organization study said. The median age of confirmed cases of the H5N1 avian flu strain was 20 years, the WHO said in a report published today in the Weekly Epidemiological Record. The death rate among patients aged 10 to 19 years was 73%, the highest of any age group, it said. Overall, the fatality rate was 56%. “The differences in the age-related case-fatality distribution among H5N1 cases are reminiscent of those observed during previous influenza pandemics, particularly in 1918, where case-fatality rates were higher among young adults,'' the study said. Disease trackers are monitoring the H5N1 virus in the event it evolves into a pandemic form capable of killing millions of people. Since late 2003, H5N1 is known to have infected at least 228 people, mainly in Asia, killing 130 of them, according to the Geneva-based WHO. Seasonal influenza kills between 250,000 and 500,000 people each year. Most fatalities occur in people over 65, according to the WHO. The study in the Epidemiological Record analyzed data on all 205 laboratory-confirmed H5N1 cases officially reported to the WHO between December 2003 and April 30 of this year. Monitoring changes in the epidemiology of human cases and the severity and characteristics of the disease may help to identify changes in the virus's ability to pass from human to human or cause different patterns of illness, the report said. “As the virus is now considered endemic in poultry in some parts of the world and continuing to spread to birds in new areas, sporadic human cases will continue to occur,'' the study said.

A severe pandemic such as the one that killed 50 million people in 1918 may take 70 million lives and cause global economic losses of as much as $2 trillion, a World Bank official said. Fatalities from H5N1 have almost tripled this year as it spread in wild birds and domestic poultry across Asia, Europe and Africa. Almost all human cases have been linked to close contact with sick or dead birds, such as children playing with them or adults butchering them or plucking feathers. Since January, at least 54 people have died from the virus in Azerbaijan, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq and Turkey, according to the WHO. That compares with 19 fatalities in Vietnam and Cambodia in the first six months of 2005. “The widespread distribution of the H5N1 virus in poultry and the continued exposure of humans suggest that the risk of virus evolving into a more transmissible agent in humans remains high,'' the report said. Half of the cases occurred among people younger than 20 and 90% occurred among those aged less than 40 years, it said. “The increased number of cases among females aged 10-29 years could indicate higher risk-exposure patterns, for example, by taking part in culling, defeathering or food preparation practices that are often carried out by specific population groups, such as young females,'' the study said. It found that while cases have occurred all year round, the epidemiological curve of H5N1 cases peaked during the cooler periods in the Northern Hemisphere. “If this pattern continues, an upsurge in cases could be anticipated starting in late 2006 or early 2007,'' it said, adding that further studies are needed to assess the relationship between climatic conditions, poultry outbreaks and associated human cases. (Bloomberg)