Bird flu claims fourth life in China

A worker arranges containers of chickens at a wholesale market on Thursday, April 4, 2013, in Shanghai, China.
BEIJING Another person has died in china from a bird flu virus that was previously never seen in humans.

A middle-aged man who transported poultry for a living has become the fourth death attributed to a new strain of bird flu in China, the government and state media reported Thursday.

The 48-year-old man, who died in Shanghai, is one of several among the infected believed to have had direct contact with fowl, which may carry the virus. Until recently, the virus, known as H7N9, was not known to infect humans.

H7N9 was named after the combination of proteins on the virus surface, and at least 14 people have been infected. Symptoms include fever and respiratory problems including severe pneumonia.

Much still remains unknown about the virus, including how people are getting infected, but scientists say it contains genetic markers that could help it infect humans. It is believed to be able to circulate in poultry stocks without sickening birds. This can allow it to spread in flocks unnoticed, making it much harder to track and also possibly creating more contamination since the birds are surviving and spending more time on farms, in markets and elsewhere. Scientists are also looking at other animals that may be hosting the virus. Pigs are one possibility because they share basic biological similarities with humans, and can serve as "mixing vessels' if infected at teh same time.

Health officials and scientists caution that there are no indications it can be transmitted from one person to another. Scientists who have studied the virus's genetic sequence said this week that the virus may have mutated, spreading more easily to other animals and potentially posing a bigger threat to humans.

Currently no vaccine exists, although the World Health Organization is working to isolate and identify possible candidate viruses to make a future vaccine. This process could take months before a dose is produced.

Guidelines issued Wednesday by the national health agency identify butchers, breeders and sellers of poultry, and those in the meat processing industry as at higher risk.

Experts only identified the first cases on Sunday. Some among the 14 confirmed cases fell ill several weeks ago but only now are being classified as having H7N9.

The government of Shanghai said that in addition to the man's death and two previously confirmed cases, there are three other suspected cases.