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Migrating geese could carry bird flu out of Asia

July 6, 2005

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) – The spread of avian flu virus among
migrating geese and other birds at a wildlife refuge in China
means the birds could carry the devastating virus out of Asia,
scientists reported on Wednesday.

This makes avian flu even more of a global threat than it
already is, the scientists said in reports published jointly by
the journals Science and Nature. Health officials fear avian
influenza could cause a pandemic of human disease.

At least 1,000 dead birds have been found at Lake
Qinghaihu, a protected nature reserve in western China,
according to two separate reports. United Nations scientists
said last week the number had topped 5,000.

“The occurrence of highly pathogenic H5N1 avian influenza
virus infection in migrant waterfowl indicates that this virus
has the potential to be a global threat,” Jinhua Liu of China
Agricultural University, George Gao of the Chinese Academy of
Sciences and colleagues wrote in their report in Science.

“Lake Qinghaihu is a breeding center for migrant birds that
congregate from Southeast Asia, Siberia, Australia and New
Zealand.”

The latest outbreak of the virus that started in 2003 has
killed 39 people in Vietnam, 12 in Thailand and four in
Cambodia. The World Health Organization has said the virus
would kill millions of people worldwide if it acquires the
ability to pass easily from human to human.

So far it has not, but influenza is extremely
mutation-prone.

The virus, which affects ducks with little harm but which
kills chickens, had not before been seen to transmit among wild
birds.

KEY BREEDING GROUND

“This lake is one of the most important breeding locations
for migratory birds that overwinter in Southeast Asia, Tibet
and India,” Gao’s team wrote.

“Several species were infected, including the bar-headed
goose (Anser indicus), great black-headed gull (Larus
ichthyaetus) and brownheaded gull (Larus brunnicephalus).”

One of the symptoms seen in the wild birds was diarrhea,
which could mean the virus would spread in contaminated water.

Yi Guan of the University of Hong Kong and colleagues did a
genetic analysis of the virus taken from the dead birds and
found it is closely related to the strain that has caused human
illness in Thailand and Vietnam.

But the sequences appeared to have mutated slightly, they
added.

“This outbreak may help to spread the virus over and beyond
the Himalayas and has important implications for developing
control strategies,” they wrote in their report, published in
Nature.

It spread quickly, causing paralysis and staggering, they
said.

“By 4 May, bird mortality was more than 100 a day; by 20
May, the outbreak had spread to other islets, with some 1,500
birds dead.”

Their genetic analysis suggested the virus was introduced
just one time to the lake, meaning a single infection could
have spread quickly.

The outbreak could burn itself out, but the large migratory
bird population at the lake made this unlikely, they wrote.

“The viruses might also move to other migratory species
that could act as carriers, remaining highly pathogenic for
domestic chickens and possibly humans.”

United Nations officials said on Tuesday that bird flu is
entrenched in Asia and predicted it would take up to a decade
to rid the region of the virus.

At a meeting in Kuala Lumpur, they said more than $100
million would be spent over the next three years on improving
the detection and reporting of outbreaks, and in combating the
virus.