Human infection with avian influenza A(H7N9) virus – China
On 18 March 2016, the National Health and Family Planning Commission (NHFPC) of China notified WHO of 29 additional laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus, including 11 deaths.
Onset dates range from 17 January to 19 February. Cases range in age from 21 to 78 years, with a median age of 57 years. Of these 29 cases, 22 (76%) are male. The majority (24 cases, 83%) reported exposure to live poultry, slaughtered poultry, or live poultry markets; the exposure history of 5 cases is unknown or with no clear exposure to poultry. Cases were reported from 6 provinces and municipalities: Zhejiang (7), Hunan (7), Jiangsu (6), Guangdong (4), Fujian (3) and Shanghai (2).
Three clusters were reported:
- The first cluster consists of two 35-year-old males (twin brothers) from Jiangsu Province, the onset dates are respectively 19 January and 1 February. Both have no clear known history of exposure to poultry.
- The second cluster consists of a 29-year-old male from Zhejiang Province and a 56-year-old female (son and mother) from Fujian Province. The onset dates are 4 February and 15 February, respectively. Both have history of exposure to live poultry market.
- The third cluster consists of a 21-year-old female and a 26-year-old male (sister and brother) both from Jiangsu Province, the onset dates are 14 February and 19 February, respectively. The brother reported exposure to live poultry. The sister took care of her brother and has no known history of exposure to poultry.
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 previously 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 continues to assess the epidemiological situation and conduct further risk assessment based on the latest information.
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.