Illegal market source of Canada's H5N1 case?
TORONTO - Canada's first H5N1 flu patient may have contracted the bird flu virus passing through or near an illegal live bird market in Beijing, Chinese scientists have suggested.
And Canadian researchers have published a report on the full genetic sequence of virus taken from the Alberta woman, who died in early January after returning from a three-week trip to her native China.
The woman was in China from Dec. 6 to 27; on her return flight home she began to experience malaise, chest pain and fever. She went to hospital the day after her return; there she was diagnosed with pneumonia and sent home with antibiotics. Four days later she returned and was admitted. She died on Jan. 3.
The woman was the first case of H5N1 infection discovered in North America. Over the past decade the virus has infected at least 650 people in 16 countries. Nearly 60 per cent — 386 — of known cases have succumbed to the infection.
The source of the woman's infection has been a mystery. She spent her entire trip in Beijing, where H5N1 reportedly hasn't been discovered for some time. And her travelling companion said the woman did not have contact with live birds while in Beijing.
Now scientists from Beijing's Center for Disease Prevention and Control have hypothesized that the woman may have contracted the virus by walking through or near market stalls that surreptitiously sell live poultry.
Beijing banned live poultry markets in 2005. But an illegal trade in prized live birds continues in the city, the authors said in a letter to Journal of Infection.
"Although the Beijing government makes efforts to ban the illegal dealing of live poultry, this selling mode consistently exists as many Chinese people prefer live poultry to fresh poultry in light of their culture of consumption," said the authors, some of whom are affiliated with the Beijing Research Center for Preventive Medicine.
The scientists pointed to the case of a previous H5N1 patient in Beijing, a woman who died in early January 2009. She had bought a live duck at a market in Hebei province, near Beijing, and prepared it for cooking by defeathering it and gutting it.
Public health investigators trying to trace the source of her infection could not test the duck; nothing of it remained by the time her infection was diagnosed. But they tested the area around the market stall where the woman bought the duck; that work revealed the presence of H5N1 viruses that were closely related to the ones that infected her.
As well, they note that several human infections with the newer H7N9 bird flu virus have been reported in Beijing, again despite the fact that live poultry sales are not supposed to be taking place.
The scientists suggested the illegal trade in live poultry in Beijing may pose a high risk of human infection with bird flu viruses for people living in the city.
"The enhanced inspection of illegal selling of live poultry, the strict regulation of transporting live poultry from regions outside of Beijing as well as the health education on changing dietetic culture is greatly warranted in Beijing in order to reduce the risk of infection with avian influenza viruses in the general population of Beijing including visiting foreigners," they wrote in their letter.
Meanwhile, scientists from Alberta's provincial laboratory, the U.S. Centers for Disease Control and the Public Health Agency of Canada's National Microbiology Laboratory in Winnipeg have published an analysis of the full genetic sequence of the virus recovered from the Alberta woman.
Their report will be in the May issue of the CDC's journal Emerging Infectious Diseases, but it has been published early online.
They said the virus is from a clade — a subgroup of the main H5N1 family — that has been found recently in China, Vietnam and Indonesia. Analysis suggested the virus is a close match for one that has been made into a vaccine seed strain that manufacturers could use if H5N1 vaccine is required.
The authors said additional study of the virus is needed to see if its characteristics are responsible for the unusual symptoms the Alberta woman suffered.
While she had the respiratory infection that is characteristic of influenza infection, she also had evidence of meningoencephalitis, infection in the brain.
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