Bird flu can more easily infect people
The H5N1 bird flu virus has mutated to infect people more easily, although it still has not transformed into a pandemic strain, researchers said Thursday.
The changes are worrying, said Dr. Yoshihiro Kawaoka of the University of Wisconsin, Madison.
“We have identified a specific change that could make bird flu grow in the upper respiratory tract of humans,” said Kawaoka, who led the study. “The viruses that are circulating in Africa and Europe are the ones closest to becoming a human virus.”
Recent samples taken from birds in Africa and Europe all carry the mutation, Kawaoka and colleagues report in the Public Library of Science journal PLoS Pathogens.
The H5N1 avian flu virus, which mostly infects birds, has infected 329 people in 12 countries since 2003, killing 201. It rarely passes from one person to another, but if it acquires the ability to do so easily, it may cause a global epidemic.
Birds usually have a body temperature of 106 degrees, humans 98.6 degrees. It’s about 91.4 degrees in the human nose and throat, where flu viruses usually enter. “So usually the bird flu doesn’t grow well in the nose or throat of humans,” Kawaoka said.
This particular mutation allows H5N1 to live well in the cooler temperatures of the human upper respiratory tract.
H5N1 caused its first mass die-off among wild waterfowl in 2005 at Qinghai Lake in China.
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