Migrating birds may pick up frozen flu virus

WASHINGTON —  Influenza virus can live for decades and perhaps even longer in frozen lakes and might be picked up and carried by birds to reinfect animals and people, researchers reported Tuesday.

Such frozen viruses could potentially become the source of new epidemics that sicken and kill generations after they were last seen, the researchers report in the Journal of Virology.

“We’ve found viral RNA in the ice in Siberia, and it’s along the major flight paths of migrating waterfowl,” said Dr. Scott Rogers of Bowling Green State University in Ohio.

“The lakes are along the migratory flight paths of birds flying into Asia, North America, Europe and Africa,” the researchers wrote.

Migrating birds are blamed, in part, for the spread of H5N1 avian influenza, which has killed or forced the culling of more than 200 million birds globally.

Since January, H5N1 has spread out of Asia, across Europe and into Africa. Now more than 50 countries have battled the virus, which has infected 258 people and killed 153 since 2003.

Experts fear it could mutate into a form that easily infects people and causes a pandemic. There were three such pandemics in the last century and one, the 1918-19 pandemic, killed 40 million to 100 million people.

It was caused by a virus called H1N1, a descendant of which still circulates and causes illness today. But the original form was only recently studied and was recovered from the still-frozen body of a victim from Alaska.

Were that strain of H1N1 to circulate today, it could cause another serious pandemic because no one alive has immunity to it, Rogers said. The original H1N1 appears to have passed fairly directly from birds to people.

Rogers noted that experts try to predict every year which strains of flu virus will be circulating, and they advise companies to formulate the next year’s flu vaccine accordingly.

“Sometimes they’re wrong,” he said. “We thought that by looking at what’s melting and what birds are picking up,” better guesses for the next year might be possible.