A top health official in China says it is possible that a deadly, new strain of bird flu could spread among humans, but cautioned there is no reason to fear a widespread pandemic.
Feng Zijian, a director at the Chinese Center for Disease Control and Prevention, says human-to-human transmission of the H7N9 strain of bird flu is possible in theory, though highly sporadic.
China has reported 17 deaths since the virus was reported in humans for the first time last month. In total, 82 people have been infected, most were near Shanghai.
Until now, the virus was believed to have only been transmitted from birds to humans, greatly limiting its ability to spread. But officials say 40 percent of those infected appear to have had no contact with poultry.
The World Health Organization confirmed the finding, but warned there is no evidence of "sustained human-to-human transmission."
John Oxford, a professor of virology at Queen Mary University of London, tells VOA he is not overly concerned the situation will spiral out of control. He says many of those infected may not have realized they came into contact with birds.
"It could be their friend who is working with chickens, whose got his fingers and hands covered in chicken down," he said. "So it's not necessarily a real person to person transmission, you're both getting it from the same source."
Of particular interest is a case involving an 87-year-old Chinese man who suffered China's first human death from H7N9. One of his sons was confirmed to have contracted the virus, and recovered. Another son later died, though the cause of his death is unclear.
Chinese authorities are investigating whether cases like this mean long-term and unprotected exposure to the infected person might result in a person-to-person transmission.
But Oxford says even if this is the case, that does not mean that the virus will easily spread quickly outside the family.
"The family is a very unique structure - people share things, share towels, even toothbrushes, and live very closely together, and the hygiene can be quite low. So you can't base a whole philosophy of what's going to happen [with a virus] based on a family transmission," he said.
China has been working on developing vaccines and other treatment for the virus, as part of a wider plan to combat any potential outbreak. It has also slaughtered thousands of birds and closed many poultry markets in an attempt to slow the spread of the disease.
This is believed to be the first time humans have contracted the H7N9 bird flu virus. It previously existed only in birds. The more common strain of avian flu, H5N1, has killed more than 360 people worldwide in the last decade.
China is considered one of the countries at greater risk for bird flu because it has the world's biggest poultry population and many chickens in rural areas are kept close to humans.