Experts unclear how China bird flu infects humans
Beijing: Almost three weeks after China reported finding a new strain of bird flu in humans, experts are still stumped by how people are becoming infected when many appear to have had no recent contact with live fowl and the virus isn`t supposed to pass from person to person.
The uncertainty adds to challenges the Chinese government is facing in trying to control the spread of the H7N9 bird flu virus that has already killed 17 people and infected 66 others in the country, mostly along the eastern seaboard.
"To me, the biggest question is the link between the virus in birds and how it gets to humans. This is not clear," said Dr Bai Chunxue, a prominent respiratory expert in Shanghai who treated one of the first cases of the virus, a family cluster involving an 87-year-old man and his two sons. Bai said other family members he talked to said the patients had no contact with birds or poultry.
"So this is indeed a mystery," Bai said in a telephone interview.
Theories among experts about how the virus may be spreading run from the ways poultry is slaughtered in markets to infected droppings from migratory birds.
Understanding how the H7N9 bird flu virus is spreading is a goal of international and Chinese experts assembled by the World Health Organisation as they begin a weeklong investigation Friday.
Helen Yu, the World Health Organisation`s spokeswoman in China, said the experts, who started arriving today, will visit laboratories and affected areas in Beijing and Shanghai.
China announced the first known cases on March 31, sparking concern among experts worldwide because it was the first time the H7N9 strain of bird flu has been known to infect humans. They fear the virus could mutate in a way that allows it to spread easily among people, but so far there has been no sign of sustained human-to-human transmission.
Chinese health officials have said people may be getting sick from direct contact with infected live birds, pointing to cases of patients who have been working in the poultry trade. The virus has been detected in live poultry, leading to mass slaughters and closures of live fowl markets.
However, as China continues to report new cases, about 40 per cent of patients have no apparent history of exposure to poultry or other birds, making the virus "very difficult to understand," said Dr. Masato Tashiro, director of WHO`s influenza research center in Tokyo.
Tashiro noted that proof of the assertion that contact with birds is causing the cases is missing. "They didn`t show any direct evidence. That`s only speculation still. It`s possible, likely, but there`s no evidence," he said.