New bird flu cases revive fears of human pandemic

India, Bangladesh, Vietnam and mainland China also experienced new outbreaks in December. During the same period, four new human cases -- in Egypt, Cambodia and Indonesia -- were reported to the World Health Organization. A 16-year-old girl in Egypt and a 2-year-old girl in Indonesia have died.

The new cases come after a two-year decline in the number of confirmed human deaths from H5N1 bird flu and as fewer countries are reporting outbreaks among poultry. A United Nations report released in October credits improved surveillance and the rapid culling of potentially infected poultry for helping to contain and even prevent outbreaks in many countries.

Yet H5N1 has continued to "at the very least smolder, and many times flare up" since the chain of outbreaks began in 2003, said Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota in Minneapolis.

The year-end uptick is a reminder of how quickly the situation can turn as long as the H5N1 virus is still out there, Osterholm and other scientists said. "What alarms me is that we have developed a sense of pandemic-preparedness fatigue," he said.

H5N1 already has been a disaster for poultry farmers in Asia. Public health officials estimate that as many as half a billion fowl have been killed by the virus or culled to contain its spread, causing enormous economic strain and food shortages. But the bigger fear has always been that H5N1 would give rise to a human pandemic like the so-called Spanish flu of 1918, which killed an estimated 50 million people worldwide.

It was in Hong Kong in 1997 that the H5N1 virus was first observed to jump from chickens to humans, infecting 18 people and killing six of them, raising fears of a worldwide catastrophe. Hong Kong ordered its entire poultry population, estimated at 1.6 million birds, destroyed within three days.

A more recent chain of poultry outbreaks began in South Korea in 2003 and spread over the years to 61 countries in Asia, Africa and Europe.

To fuel a pandemic, a virus must be able to both infect humans and spread readily from person to person. The currently circulating H5N1 strain does neither well.