The World Health Organisation said yesterday that a number of people who have tested positive for a new strain of bird flu in China appear to have had no contact with poultry, adding to the mystery about a virus that has killed 17 people to date.
Chinese authorities have slaughtered thousands of birds and closed some live poultry markets to try to slow the rate of human infection, but many questions remain unsolved, including whether the H7N9 strain is being transmitted between people.
WHO spokesman Gregory Hartl confirmed that “there are people who have no history of contact with poultry”, after a top Chinese scientist was quoted as saying this applied to about 40 per cent of those infected.
“This is one of the puzzles still (to) be solved and therefore argues for a wide investigation net,” Hartl said.
Hartl added an international team of experts going to China soon would include in their investigation the possibility that the virus can be spread between people, although there was “no evidence of sustained human-to-human transmission”.
“It might be because of dust at the wet markets, it could be another animal source beside poultry, it could also be human-to-human transmission,” he said.
Wendy Barclay, an influenza expert at Imperial College London, said it could be hard to reveal or rule out exposure to poultry - or to wild birds, which could also be a possible source of infection:
“The incubation time might be quite long, so visiting a market even 14 days before might have resulted in infection.”
Hartl said two new suspected cases of possible human-to-human transmission were being investigated. The first is a couple in Shanghai who tested positive, Hartl said, adding that the wife had died and husband was still sick. A seven-year-old girl in Beijing was the first case in the capital at the weekend and the boy next door has also tested positive, but is not showing symptoms, he said.
The WHO had previously reported two suspected family “clusters”, but the first turned out to be a false alarm and the second was inconclusive.
China has warned that the number of infections, 82 so far, could rise. Most of the cases and 11 of the deaths have been in the commercial capital Shanghai.