Four-year-old child of bird-flu infected man also develops H7N9 virus

BEIJING A 4-year-old boy has developed the new H7N9 strain of bird flu, the same strain his father had been infected with.

Shandong province's health department says there is no evidence of human-to-human transmission, and that the boy is in stable condition at a hospital.

The Jinan Times newspaper says the boy's 36-year-old father had no direct contact with poultry, but that the family lives near a market that sells live poultry.

The H7N9 virus has infected 126 people in China, killing 23 of them.

Experts are watching it closely for any sign it could spark a pandemic, but say so far there is no evidence it can spread easily among people. They believe infections are caused by some kind of contact with sick birds.

"The biggest technical obstacle for prevention is that we don't know where the virus-carrying birds are or where they will go," Xu Jianguo, a researcher with the Chinese Center for Disease Control and Prevention, told the Xinhua news agency. He added the outbreak is not likely to disappear anytime soon.

Last Thursday, Chinese scientists reported for the first time that they found strong evidence of how humans became infected with a new strain of bird flu: from chickens at a live market.

For the study published April 25 in The Lancet, Chinese scientists compared swabs from birds at markets in eastern China to virus samples from four patients who caught the new H7N9 virus. The scientists found the virus from one patient was nearly identical to one found in a chicken.

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Finding definitive proof of how patients were infected is very difficult and experts have so far struggled to find much virus in birds despite taking nearly 48,000 samples from animals in live markets,. Experts had suspected birds in live markets to be the source of infection but weren't sure if other animals or wild birds might also be responsible.

Health officials have so far refrained from recommending any wide-scale slaughter of poultry to contain the disease, one of the main tools used previously to combat another bird flu strain, H5N1. Unlike that strain, H7N9 doesn't appear to sicken chickens, giving experts fewer signs as to where it might be spreading.

Chinese authorities have shut down live poultry markets in many affected regions, which seems to have slowed down the virus. Still, Taiwan reported its first caseof the virus week.