BEIJING -- Bird flu was found in a 4-year-old Beijing boy who has no symptoms of the infection, health authorities said Monday, suggesting more people may be catching the H7N9 influenza virus than reported.
The first asymptomatic H7N9 case was discovered by health care workers searching for possible cases, the Beijing Municipal Health Bureau said in a statement on its website Monday. The boy's parents are poultry and fish sellers, and their neighbors across the street had bought chicken sold by the family of a 7- year-old girl whose H7N9 infection was reported two days ago.
The boy is under medical observation. The case suggests some H7N9 infections may be going unrecorded because of a lack of obvious symptoms. Almost all the 60 previous cases in eastern China were extremely unwell, with complications extending to brain damage, multi organ failure and muscle breakdown.
"With asymptomatic cases around, I think everything changes," said Ian Mackay, an associate professor of clinical virology at the University of Queensland in Brisbane, in a telephone interview. "There has been a spike in pneumonia cases that have drawn the health officials' attention, but the virus may have been going around as a normal cold."
The boy's infection was picked up as part of contact tracing -- a process whereby relatives, neighbors and others known to have been in contact with a confirmed case are screened for the virus. The boy was one of 24 people tested in connection with the 7-year-old girl's infection.
"It's great that the authorities are showing some evidence of prospective screening of contacts, not just asking people if they are sick or not," Mackay said. "It's essential that lab testing of contacts is carried out as soon as possible to give us some information about the denominator: how many cases are positive for this virus, whether they're symptomatic or not."
The parents of the 7-year-old patient live and sell poultry in the Shunyi district of northeast Beijing. Her case was the first in northern China, demonstrating that the virus is circulating across much of the country's east.
The girl is recovering after treatment at Beijing Ditan Hospital Capital Medical University, the official Xinhua News Agency reported Sunday, citing the city's disease control and prevention center.
Her positive response shows that early treatment with proper anti-viral medication can be effective, Michael O'Leary, WHO's China representative, told reporters in Beijing Sunday.
"We know also that the virus, when untreated, is very serious," he said. "We advocate for early treatment and good medical care."
The cases in Beijing and two in Henan province widen the geographic spread of H7N9, adding impetus to the government's efforts to gauge the magnitude of the infection in poultry and wild birds.
Shanghai's government said Sunday that the virus killed two more people, taking the country's death toll from the outbreak to 13. The city also reported three fresh infections while the eastern provinces of Jiangsu and Zhejiang also confirmed new cases, raising the national tally yesterday to 60 from 49 on April 13.
Chinese Vice Premier Liu Yandong, touring Shanghai and nearby Jiangsu and Zhejiang provinces yesterday, called on medical workers to more attention to the development of the virus, speed up the study of the strain and stem the spread of the disease, the official Xinhua news agency reported today.
There's no evidence that the virus is spreading easily among people, a critical feature preventing it from developing into an epidemic. The H5N1 bird flu strain, which killed at least 371 people over the past decade, also hasn't acquired the ability to spread easily among people. In 2009, a novel swine flu virus, known as H1N1, touched off the first influenza pandemic in 41 years.
Four international flu experts will arrive in China within days to help authorities respond to the country's widening bird- flu emergency, according to two people familiar with the matter.