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The conventional wisdom when it comes to how humans generally contract the H5N1 bird flu virus is that most become infected through close, direct contact with infected birds.
Not all, but most.
A review of the expert agencies in the field show:
- Most cases of avian influenza infection in humans have resulted from direct or close contact with infected poultry or surfaces contaminated with secretions and excretions from infected birds. - The United State's CDC
- How do people become infected? Direct contact with infected poultry, or surfaces and objects contaminated by their faeces, is presently considered the main route of human infection. - WHO FAQ
- From what we know today, the avian influenza virus can be transmitted through contact among and with poultry and their droppings, feathers, intestines and blood. The greatest risk of infection for humans appears to be through the handling and slaughtering of live infected poultry. - FAO FAQ
All very reasonable and straight forward.
Even if it doesn't tell the whole story. There have always been exceptions to the rule.
Rare human-to-human transmission, suspected environmental transmission, and a certain percentage of cases where the vector was never established.
Still, contact with infected poultry is assumed to be the most common way of catching the virus. And so quite naturally, when 8 human cases were reported in mainland China last month, most observers assumed there had to be infected birds involved somewhere along the line.
Suddenly things become more than a bit messy after China's Minister of Agriculture (MOA) comes out and states that they've found no direct link between (and here it's hard to tell - some/many/all? ) of their recent human cases and infected poultry.
According to the MOA, they've checked their poultry operations, and have tested birds in the areas where human cases were reported. They claim not to have found evidence of infection.
The MOA, Yu Kangzhen, states that, "The infection sources is not clear yet."
With a poultry industry estimated at 12 billion chickens and 3 billion domestic waterfowl (ducks and geese), the Chinese have a lot riding on the ongoing efficacy of their poultry vaccination programs.
Yesterday, Dr. Zhong Nanshan - a highly respected respiratory disease specialist and a hero of the SARS outbreak - came out and said the poultry vaccine was failing to prevent infection in birds.
He warned the public to be aware that poultry can be infected with the bird flu virus but show no symptoms. Zhong went on to say, "The existing vaccines can only reduce the amount of virus, rather than totally inactivating it."
I'm sure that went over at the Ministry of Agriculture about as well as finding an infected duck paddling in the New Year's Eve punch bowl.
A vaccine failure would be catastrophic for their poultry industry, and more importantly, for hundreds of millions of Chinese consumers dependent upon these birds for food.
For now, officially, the source of these human infections remains unexplained.
Which I'm sure is a far more palatable explanation to the Minister of Agriculture than the one offered yesterday by Dr. Zhong.
China's Chief Veterinary: Human infection of bird flu has no necessary link with animal cases
www.chinaview.cn
2009-02-08 05:46:13
BEIJING, Feb. 7 (Xinhua) -- China's Chief Veterinary said on Saturday that the human cases of bird flu did not necessarily mean there would be an outbreak among poultry, in response to the international expert's doubt.
The human cases and the animal cases were not directly interlinked, which was quite common in the world. So far, 405 human cases from 15 countries have been reported, among which many occurred without the outbreak among animals. The infection sources is not clear yet, Yu Kangzhen, Chief Veterinary of the Ministry of Agriculture (MOA) told Xinhua in an interview.
The infection rate among high-risk group including those who feed, kill and sell the poultry was not very high as a matter of fact, and no such cases were reported in China, Yu said.
There is still much unchartered water in the bird flu study, which needs more scientific exploration by international researchers, he said.
Eight human cases have been reported in seven provinces in China since January. But no epidemic outbreak of the H5N1 strain of avian influenza have been found in the seven provinces, based on the researches of the overall epidemiological situation and investigations still continuing, he told Xinhua.
"The human cases show the virus must be circulating among birds," Vincent Martin, a senior technical advisor on avian flu for the UN's Food and Agriculture Organization (FAO) said Wednesday, indicating that it was not normal that there had been no confirmation or reports of outbreaks in poultry.
Such doubts intensified as poultry death was reported in Hong Kong, raising fears that the bordering Guangdong Province would be affected.
Yu said the veterinary department in Guangdong had carried out epidemiological inspection and detected no such cases. Poultry in the province were all well-vaccinated as of November 2008, according to the MOA.
The Chinese government attaches great importance to the anti-bird flu efforts. Local government are urged to report to the MOA within 24 hours after infection is defected, Yu said.
Hundreds of the monitoring centers are established across the nation to keep close watch on the outbreak of the deadly virus.
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