Bird flu virus mutating into human-unfriendly form
Pastor Dale Morgan
*Bird flu virus mutating into human-unfriendly form*
05 Oct 2007 00:00:10 GMT
Source: Reuters
By Maggie Fox, Health and Science Editor
NEW YORK, Oct 4 (Reuters) - The H5N1 bird flu virus has mutated to
infect people more easily, although it still has not transformed into a
pandemic strain, researchers said on 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," Kawaoka said.
Recent samples of virus taken from birds in Africa and Europe all carry
the mutation, Kawaoka and colleagues report in the Public Library of
Science journal PLoS Pathogens.
"I don't like to scare the public, because they cannot do very much. But
at the same time it is important to the scientific community to
understand what is happening," Kawaoka said in a telephone interview.
The H5N1 avian flu virus, which mostly infects birds, has since 2003
infected 329 people in 12 countries, killing 201 of them. It very rarely
passes from one person to another, but if it acquires the ability to do
so easily, it likely will cause a global epidemic.
All flu viruses evolve constantly and scientists have some ideas about
what mutations are needed to change a virus from one that infects birds
easily to one more comfortable in humans.
Birds usually have a body temperature of 41 degrees Celsius (106 degrees
F), and humans are 37 degrees C (98.6 degrees F) usually. The human nose
and throat, where flu viruses usually enter, is usually around 33
degrees C (91.4 degrees F).
"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 central China, where hundreds of thousands of migratory
birds congregate.
That strain of the virus was carried across Asia to Africa and Europe by
migrating birds. Its descendants carry the mutation, Kawaoka said.
"So the viruses circulating in Europe and Africa, they all have this
mutation. So they are the ones that are closer to human-like flu,"
Kawaoka said.
Luckily, they do not carry other mutations, he said.
"Clearly there are more mutations that are needed. We don't know how
many mutations are needed for them to become pandemic strains."