Human infection with avian influenza A(H7N9) virus – China
On 18 April 2016, the National Health and Family Planning Commission (NHFPC) of China notified WHO of 17 additional laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus, including 5 deaths.
Onset dates range from 21 February to 20 March. Cases range in age from 26 to 86 years, with a median age of 60 years. Of these 17 cases, 11 (65%) are male. The majority (15 cases, 88%) reported exposure to live poultry, slaughtered poultry, or live poultry markets. The exposure history of one (1) case is unknown. One (1) case is linked to a cluster of two (2) cases reported earlier to WHO (see below).
Cases were reported from 6 provinces and municipalities: Anhui (4), Jiangsu (4), Fujian (3), Guangdong (3), Zhejiang (2) and Hubei (1).
One cluster was reported. The cluster includes an 85-year-old female from Zhejiang Province. She had onset of symptoms on 1 March and passed away on 8 March. She had been admitted to the same hospital and shared the ward with a confirmed case between 22 and 23 February. She was not exposed to live poultry or live poultry market, according to her relatives.
The confirmed case admitted at the same ward was a 29-year-old male from Zhejiang Province who developed symptoms on 15 February. He had exposure to a live poultry market and a household contact who was also a confirmed case. The contact from Fujian Province developed symptoms on 4 February and had exposure to a live poultry market.
Human to human transmission between the 29-year-old male and the 85-year-old female cannot be ruled out. Further virological information is awaited.
Public health response
The Chinese Government has taken the following surveillance and control measures:
- strengthening outbreak surveillance and situation analysis;
- reinforcing all efforts on medical treatment; and
- conducting risk communication with the public and dissemination of information.
WHO risk assessment
Most human cases are exposed to the A(H7N9) virus through contact with infected poultry or contaminated environments, including live poultry markets. Since the virus continues to be detected in animals and environments, further human cases can be expected. Although small clusters of human cases with influenza A(H7N9) viruses have been reported including those involving healthcare workers, current epidemiological and virological evidence suggests that this virus has not acquired the ability of sustained transmission among humans. Therefore further community level spread is considered unlikely.
Human infections with the A(H7N9) virus are unusual and need to be monitored closely in order to identify changes in the virus and/or its transmission behaviour to humans as it may have a serious public health impact.
WHO advises that travellers to countries with known outbreaks of avian influenza should avoid poultry farms, contact with animals in live bird markets, entering areas where poultry may be slaughtered, or contact with any surfaces that appear to be contaminated with faeces from poultry or other animals. Travellers should also wash their hands often with soap and water. Travellers should follow good food safety and good food hygiene practices.
WHO does not advise special screening at points of entry with regard to this event, nor does it currently recommend any travel or trade restrictions. As always, a diagnosis of infection with an avian influenza virus should be considered in individuals who develop severe acute respiratory symptoms while travelling or soon after returning from an area where avian influenza is a concern.
WHO encourages countries to continue strengthening influenza surveillance, including surveillance for severe acute respiratory infections (SARI) and to carefully review any unusual patterns, in order to ensure reporting of human infections under the IHR (2005), and continue national health preparedness actions.