Hong Kong reported its first case of a form of bird flu that killed 45 people in eastern China, suggesting the virus is spreading further south in poultry.
The 36-year-old Indonesian domestic helper, who was infected with the new H7N9 flu strain, remains in critical condition, Ko Wing-man, the city’s health secretary, told reporters today. She had traveled to the neighboring mainland Chinese city of Shenzhen, where she bought and slaughtered a chicken, the government said yesterday.
Her infection suggests the virus, which is often lethal to humans but causes no symptoms in birds, is circulating less than 30 miles from downtown Hong Kong. The city’s government curbed live poultry sales 16 years ago to prevent an earlier bird-flu variant from spreading.
“Respiratory viruses do their own thing; they don’t respect boundaries,” Ian Mackay, an associate professor of clinical virology at the University of Queensland in Brisbane, Australia, said by phone. “It does seems that it’s continuing to add to provinces and regions, rather than reappear in all the old places it started in back in February and March.”
Yesterday, the city elevated the response level under its influenza pandemic preparedness plan to “serious,” prompting public hospitals to activate a “serious response” alert today and step up infection controls.
People who have had close contact with the patient, including her travel companion to Shenzhen, tested negative for the virus, Ko said today. Health authorities will continue tracing the victim’s contacts, he said.
Chris Cheung, a spokesman for Hong Kong’s Department of Health, declined to elaborate on the circumstances around which the patient was probably infected. The patient visited Shenzhen on Nov. 17.
She had a history of “traveling to Shenzhen, buying a chicken, slaughtering the chicken and eating the chicken,” Ko said yesterday.
Shenzhen is a 61-minute train ride from the downtown Central district of Hong Kong and a popular day-trip destination for shopping and dining. Last year, Hong Kong residents departed from the Lo Wu check point 35.4 million times, according to the census and statistics department. The city has 7.15 million residents, according to a government fact sheet.
Human cases of H7N9 in China date back to February and surged in April before agriculture authorities temporarily closed live poultry markets and quarantined farms to limit human exposure. The Geneva-based World Health Organization counted 139 laboratory-confirmed cases as of Nov. 6.
“We might not expect that this case is the only infection” in Shenzhen, said Ben Cowling, associate professor of infectious disease epidemiology at the University of Hong Kong’s School of Public Health.
H7N9 has previously turned up outside mainland China. In late April, officials in Taiwan reported a case in a 53-year-old man who had just returned to Taiwan via Shanghai after a business trip to the eastern city of Suzhou.
Technical difficulties in detecting H7N9 infections may be causing cases to go unreported, Cowling said. Residents of Guangdong, the Chinese province bordering Hong Kong, appear to have a greater preference for buying live poultry than those of other provinces, he said.
While H7N9 hasn’t mutated to become as contagious as seasonal flu, strains that emerge in China are of special interest to researchers. The 1957-58 Asian Flu and 1968-69 Hong Kong Flu pandemics were first identified in the world’s most populous nation, and an earlier bird flu strain known as H5N1 may have come from the southern province of Guangdong in 1996. Years later, a new seasonal flu was found in neighboring Fujian and triggered epidemics worldwide.
To control an outbreak of H5N1 in 1997, Hong Kong authorities culled about 1.5 million chickens to remove the source of the virus. The order was made by Margaret Chan, then Hong Kong’s director of health, who is now WHO director-general in Geneva. The measure later became the global standard for the control of avian influenza.
Many families in rural areas kept chickens in their yards in wood-and-wire hutches that can still be seen lying empty and rusting in villages across the territory. Ducks, geese and pigeons are also widely eaten in Hong Kong.
Detection of H7N9 has been complicated as chickens and ducks don’t get sick from the virus.
Shanghai will suspend live poultry trading from January 31, the first day of the Chinese New Year, until April 30 to prevent a recurrence of the bird flu, the official news agency Xinhua reported yesterday. Hong Kong’s government has suspended the importation of live chickens from three Shenzhen farms, according to yesterday’s statement.
Hong Kong officials will visit poultry farms and live chicken stalls in markets to ensure compliance.
The city’s government said it has notified mainland health authorities and WHO about the confirmed infection.
“The big thing is if animal contact and the slaughtering of animals can be minimized, the risk of infection is going to be reduced,” said the University of Queensland’s Mackay. “If markets could be shut down or changed in the way they work, I’m sure the spread of H7N9 would take the same sort of dive that it did earlier in the year.”