Looking to poultry for warning signs of a possible bird flu threat to humans has proved a success in the past. In 2003, H5N1 swept through Asian bird flu populations, forewarning humans. A dead bird sighting then became a cause for alarm around the world.
Not all viruses leave any signs as obvious as dead birds though. In fact, the ideal for a virus is to keep the host alive for a long time to maximize the chance of spreading to another victim. There are now indications that the H7N9 strain that has popped up in China fits this ideal model when it resides in birds, and possibly pigs. Laboratory tests seem to show birds can be infected without showing obvious symptoms. For health authorities trying to track the virus, this creates issues.
"If this continues to spread throughout China and beyond, it would be an even bigger problem than with H5N1 in some sense, because with H5N1 you can see evidence of poultry dying. Here you can see this would be more or less a silent virus in poultry species that will occasionally infect humans," University of Hong Kong microbiologist Malik Peiris told the Associated Press. It is as yet unable to then make the leap from human to human though.
Even with this transmission limitation the virus has reportedly killed three people. The outbreak has prompted vaccine manufacturers to again ready for the possible initiation of immunization programs. Taipei Times reports the chairman of Taiwanese drugmaker Adimmune believes the company could produce up to 10 million doses of a vaccine within two months. While there is as yet no vaccine for H7N9, the strain is similar to H5N1, for which a preventive was produced after the last outbreak.