The H7N9 virus shows little or no clinical symptoms in poultry, complicating detection. But authorities should have stepped up their surveillance going into the peak season, the experts said.

“Work should be done even before the first human case is found each year,” Professor Malik Peiris, a public health virologist at the University of Hong Kong, said.


“Local governments should step up in regulating farm and market inspection, instead of only reacting by closing down markets once cases are detected.”

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Peiris doubted whether all provincial governments had ­carried out strict, regular checks of local live poultry markets, which he said was the most effective way to prevent human infection.

The response at the local level to the outbreak has varied. ­Zhejiang has shut down its live poultry markets, while cities in Jiangsu have also suspended sales. Guangdong has suspended the sale of poultry from high-risk areas and ordered each city to restrict the trade.

Dr Bernhard Schwartlander, the World Health Organisation’s representative in China, said the outbreak had come earlier this year, marked by “a steep increase” in the number of human ­infections.

A vaccinator sprays disinfection liquid to chicken cages at a live poultry market in Hefei city, Anhui province on Feb. 16, 2017. Up to Feb 16, 20 people had died from H7N9 in the province. Photo: China News Service

Schwartlander said the closure of live bird markets, together with other measures to maintain market hygiene, appeared to have been a key factor in controlling previous outbreaks.

Gao Fu, a professor at the Institute of Microbiology affiliated with the Chinese Academy of Sciences, said authorities had lowered their guard after the last two years when outbreaks were less severe.

“The measures needed to prevent [the spread of] bird flu are quite clear: shut down live poultry markets,” Gao said.


“We have advocated permanent closure of live poultry markets and for only quarantined chicken to be traded, but the ­enforcement is lagging.”

Mutations of the virus have been reported in Guangdong. The Chinese Centre for Disease Control and Prevention has ­informed the WHO that the mutation was found in samples collected from two patients in the province last month.


The WHO believes the mutation is only a risk to poultry and there was no evidence the change had allowed the virus to spread more easily among people, Schwartlander said.

Additional reporting by Kinling Lo