Doctors in China are trying to establish how people are being infected with a lethal strain of bird flu.
Seventeen people have died and 66 more have been infected with the H7N9 virus.
There are growing fears it might be able to pass from human to human as some of the newest patients have had no contact with poultry.
Al Jazeera's Rob McBride reports from Hong Kong.
Source: Al Jazeera