BEIJING -- The case of bird flu in a 4-year-old Beijing boy who displayed no symptoms is adding to the unknowns about the latest outbreak that has caused 63 confirmed cases and 14 deaths, health officials say.

The boy, who tested positive for the H7N9 virus, is considered a carrier of the strain and has been placed under observation to see if he develops symptoms. He was found in a check of people who had contact with a 7-year-old girl who was confirmed last weekend as Beijing's first case of H7N9. A neighbor of the boy had bought chicken from the girl's family.

As puzzling as the case is, the boy does add another data point to medical experts' limited understanding of H7N9, said Beijing Health Bureau deputy director Zhong Dongpo.

"This is very meaningful because it shows that the disease caused by this virus has a wide scope. It's not only limited to critical symptoms. There can also be slight cases, and even those who don't feel any abnormality at all," Zhong said.

The H7N9 strain was not previously known to infect humans before cases turned up in China this winter. Medical experts still say no evidence exists that it can be passed from one person to another. Making the virus hard to detect is that infected poultry display slight or no symptoms, unlike the H5N1 strain, which kills birds and raged across the region a decade ago. -- AP

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