Chinese researchers are suggesting Canada's first H5N1 flu patient may have contracted the bird flu virus passing through or near an illegal live bird market in Beijing.

And Canadian scientists 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.

China Bird Flu

It's possible an Alberta woman was infected while passing market stalls that surreptitiously sell live poultry, Chinese scientists say. (Associated Press) ( Associated Press)

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 she did not have contact with live birds while there.

But scientists from Beijing's Centre for Disease Prevention and Control are hypothesizing that illegal live bird markets may have been the source of the woman's infection.

In a letter to the Journal of Infection, they say that even though Beijing banned live poultry markets in 2005, an illegal trade in live poultry continues in the city.

They say it is possible the woman was infected while passing market stalls that surreptitiously sell live poultry.

It is the custom in China to eat chicken when it has been freshly killed, and the sale of live poultry remains common in many parts of the country.

The scientists point to a previous H5N1 case 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.

Testing of the area around the market stall where the woman bought the duck 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.

Call for more inspections in Beijing

The scientists suggest 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 write in their letter.

Meanwhile, scientists from Alberta's provincial laboratory, the University of Calgary, University of Alberta in Edmonton, 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 say the virus is from a clade — a subgroup of the main H5N1 family — that has been found recently in China, Vietnam and Indonesia. Analysis suggests 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 say 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.