Lethal Strain of Avian Flu Is Reported Found in Pigs in China

[David Farber <dave () farber net>]

Begin forwarded message:



Lethal Strain of Avian Flu Is Reported Found in Pigs in China

August 21, 2004
 By KEITH BRADSHER





HONG KONG, Aug. 20 - A senior Chinese health official
disclosed on Friday that her country had found a lethal
strain of avian influenza among pigs at several farms, a
discovery that could move the virus a step closer to
becoming a potentially deadly problem for people.

The discovery of the bird flu strain in pigs is alarming,
health officials said, because scientists have long
regarded pigs as an important conduit for new influenza
strains to infect people.

Chen Hualan, the chief of the China National Avian
Influenza Reference Laboratory, made the disclosure at a
World Health Organization conference in Beijing and
confirmed it in a brief telephone interview on Friday, but
declined to provide details.

The A(H5N1) strain of avian influenza, or bird flu,
infected chickens in at least eight countries earlier this
year, and killed 23 of the 34 people in Thailand and
Vietnam who caught the disease directly from sick chickens.
But the virus did not appear to evolve the ability to pass
readily from person to person.

The slaughter of more than 100 million chickens this spring
seemed to bring the disease under control. But it has
reappeared this summer, killing the three people who are
confirmed to have caught it in recent days in Vietnam.

Hong Kong and Chinese officials announced separately on
Friday that China had temporarily suspended shipments of
chilled ducks and geese to Hong Kong from neighboring
Guangdong Province earlier this month. The Hong Kong
government said this was to check whether ducks and geese
there had avian influenza; China has not acknowledged any
such cases.

Most kinds of influenza viruses live only in birds, not
people. But pigs can be infected with both bird strains and
human strains of influenza. When these viruses mix and
reassort genes inside a pig, the result can be a new virus
for which people have little immunity.

Many scientists believe that the great flu pandemics of the
20th century - the Spanish influenza of 1918-19, the Asian
flu of 1957-58 and the Hong Kong flu of 1968-69 - began
when new flu strains moved from birds to people. Estimates
of worldwide deaths from the Spanish influenza range from
20 million to 100 million, while the next two pandemics
together killed 4 million to 5 million people.

Juan Lubroth, a senior animal health official at the
headquarters of the Food and Agriculture Organization in
Rome, said several critical details were not available from
China about the latest discovery.

Most important is whether the flu virus was living and
replicating in pigs, and was isolated from their tissues.
If the virus was detected using only genetic techniques
then it is possible the pigs were contaminated with the
virus, possibly by inhaling it from poultry feces, but had
not actually been infected with it, Mr. Lubroth said.

If the pigs are infected, then it would be important to
determine if they became sick as a result, he said.

If the pigs stay healthy even when they are infected, then
the disease may have lost some of the deadliness that it
shows in birds. But infected yet healthy pigs may also be
harder to spot and quarantine or cull.

Roy Wadia, a spokesman in Beijing for the World Health
Organization, said it would also be important to learn
whether the virus had evolved the ability to pass from pig
to pig, which would suggest that it could pass more readily
among mammals and perhaps people.

A press official at China's Agriculture Ministry, which is
responsible for avian influenza issues, expressed surprise
when told of Ms. Chen's remarks and said his office did not
have any information about the disease in pigs. An official
at the China National Avian Influenza Reference Laboratory,
in Harbin, said Ms. Chen was the only laboratory official
allowed to speak publicly about the issue.

While Mr. Wadia and Mr. Lubroth declined to speculate on
the probability that a pig infection would allow the virus
to spread to people, another international health official
said, "If this pig thing is right, it's another step down
the road to pandemic."

The A(H5N1) virus has infected chickens in China, Vietnam
and Thailand in the last two months. This week, Malaysia
found the virus in chickens near the Thai border, while
Thailand found it in ducks.

A spokeswoman for the Hong Kong government said the
territory imported 5,200 live pigs a day from specially
registered and inspected farms in China. Random blood
samples have not found any of the pigs infected with
A(H5N1), she said.

Ms. Chen did not specify where the infected pigs were. But
she has previously published papers based on research in
Fujian Province, northeast of Guangdong Province.

http://www.nytimes.com/2004/08/21/international/asia/21flu.html? 
ex=1094103706&ei=1&en=a499622acd8e5ca6

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