Symptom-Free Bird Flu Case Suggests Wider H7N9 Spread

Bird flu was found in a 4-year-old Beijing boy who has no symptoms of the infection, health authorities said, 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 today. 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 of the 64 people diagnosed with the virus so far have been 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 today. “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.

Sick or Not?

“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 yesterday, citing the city’s disease control and prevention center.

Positive Response

Her positive response shows that early treatment with proper antiviral medication can be effective, Michael O’Leary, WHO’s China representative, told reporters in Beijing yesterday.

“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 reported two deaths yesterday, and another was reported in Jiangsu today, taking the country’s death toll from the outbreak to 14.

Chinese Vice Premier Liu Yandong, touring Shanghai and nearby Jiangsu and Zhejiang provinces yesterday, called on medical workers to pay 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.

A new case was detected in Zhejiang today, and another infection was reported in a 60-year-old man in Anhui province, the local health departments said on their websites.

Human Vectors?

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.

A surge in bird flu cases in China increases the pandemic potential of the H7N9 strain, according to a Beijing-based supplier of influenza vaccines to the Chinese government.

Sinovac Biotech Ltd., the first company to win regulatory approval for a swine flu shot in 2009, is preparing to make immunizations against the new virus. The Nasdaq-traded company will hold off producing the shots until it’s received an order from the state, said Chief Executive Officer Yin Weidong.

Pandemic Threat

“The risk of this becoming a pandemic is increasing,” Yin said in an interview at the company’s headquarters in the Chinese capital, where a second H7N9 infection was reported today.

Sinovac has notified its suppliers that it may need to order additional fertilized chicken eggs to produce H7N9 vaccine, Yin said.

Under an agreement with China’s Food and Drug Administration, a Sinovac vaccine for pandemic flu doesn’t need to undergo clinical testing because its production methods have already been approved and the pandemic flu vaccine would represent only a change in the viral strain, he said.

Based on typical vaccine development and production schedules, batches could be ready for commercial use as early as late July, Yin said, adding that he is urging the World Health Organization and its affiliated labs to expedite the preparation of seed strains.

Sinovac has the capacity to produce about 30 million to 40 million doses of flu vaccine annually, said Yin, who founded the company in 2001 to make immunizations for hepatitis. The price to the Chinese government is about 20 yuan ($3.23) a piece, he said.

Experts Fly In

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.

Nancy Cox, director of the flu division at the Centers for Disease Control and Prevention in Atlanta; Anne Kelso, director of a World Health Organization center for flu research in Melbourne; Malik Peiris, chairman of virology at the University of Hong Kong; and Angus Nicoll, head of the Stockholm-based European Centre for Disease Prevention and Control’s flu program, will arrive midweek to offer technical advice, said the people, who declined to be identified because the Chinese government hasn’t announced that the experts are being invited.

The group will seek to assist Chinese authorities grappling to identify the source and mode of transmission of the H7N9 avian influenza.

Cox referred questions to the WHO, while Kelso, Peiris and Nicoll didn’t respond to e-mails seeking comment. Gregory Hartl, a spokesman for the Geneva-based WHO, said the agency has discussed a mission to China, but declined to comment on specifics. Two calls to the press office of China’s National Health and Family Planning Commission weren’t answered.

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