40% of Bird Flu Victims Didn't Touch Birds: Report Finding raises fears that it's passing human-to-human By Kevin Spak, Newser Staff Posted Apr 18, 2013 11:25 AM CDT 7 comments Comments Nurses collect patients' blood samples at a specialized fever clinic inside the Ditan Hospital, where a Chinese girl is being treated for the H7N9 strain of bird flu, in Beijing, April 14, 2013. (AP Photo/Andy Wong) (Newser) – H7N9 is growing no less mysterious: Roughly 40% of those infected in China's bird flu outbreak have never actually come in contact with poultry, according to a leading Chinese scientist, and the World Health Organization yesterday backed up that claim. WHO spokesman Gregory Hartl acknowledged "there are people who have no history of contact with poultry. ... This is one of the puzzles still (to) be solved," he tells Reuters. "It might be because of dust at the wet markets, it could be another animal source besides poultry, it could also be human-to-human transmission," though he added that there was still "no sustained evidence" of the latter. Officials are keeping a watchful eye on three Shanghai families and two boys in Beijing that they suspect may have infected each other, Hartl tells the New York Times, but he cautioned that even if members of the same family tested positive, it wouldn't be conclusive. The Times reports there's also growing concern that the virus may not have originated in birds, but in another animal. But China maintains that live poultry markets are the source; it's collected 47,801 samples from 1,000 such markets and farms to prove it. But only 39 tested positive, a number that Hartl notes is low.