Human infection with avian influenza A(H7N9) virus – China
On 5 May 2017, the National Health and Family Planning Commission of China (NHFPC) notified WHO of 24 additional laboratory-confirmed human infections with avian influenza A(H7N9) virus in China.
Details of the cases
Onset dates ranged from 14 to 29 April 2017. Of these 24 case patients, nine were female. The median age was 56.5 years (range 25 to 82 years). The case patients were reported from Anhui (1), Beijing (1), Chongqing (2), Gansu (1), Guangxi (1), Hebei (7), Henan (1), Hubei (1), Hunan (1), Jiangsu (1), Sichuan (6) and Shaanxi (1). This is the first case reported in Shaanxi since the virus emerged in 2013.
At the time of notification, there were nine deaths, 13 case patients were diagnosed as having either pneumonia (2) or severe pneumonia (11), and two case patients were still being investigated. Nineteen case patients were reported to have had exposure to poultry or live poultry market, and two had no known poultry exposure. The exposure history was still being investigated for three case patients. No case clustering was reported.
To date, a total of 1463 laboratory-confirmed human infections with avian influenza A(H7N9) virus have been reported through IHR notification since early 2013.
Public health response
Considering the increase in the number of human infections since December 2016, the Chinese government at national and local levels is taking further measures which include:
- Strengthening risk assessment and guidance on prevention and control focusing on the most affected and newly affected areas;
- Continuing to strengthen control measures focusing on hygienic management of live poultry markets and cross-regional transportation;
- Conducting detailed source investigations to inform effective prevention and control measures;
- Continuing to detect and treat human infections with avian influenza A(H7N9) early to reduce mortality;
- Continuing to carry out risk communication and issue information notices to provide the public with guidance on self-protection; and
- Strengthening virology surveillance to better understand levels of virus contamination in the environment as well as mutations, in order to provide further guidance for prevention and control.
WHO risk assessment
The number of human infections with avian influenza A(H7N9) and the geographical distribution in the fifth epidemic wave (i.e. onset since 1 October 2016) is greater than in earlier waves. This suggests that the virus is spreading, and emphasizes that further intensive surveillance and control measures in both the human and animal health sector are crucial.
Most case patients are exposed to avian influenza 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, and live poultry vending continues, further human infections can be expected. Although small clusters of human infection with avian influenza A(H7N9) virus have been reported including those involving patients in the same ward, current epidemiological and virologic evidence suggests that this virus has not acquired the ability of sustained transmission among humans. Therefore the likelihood of further community level spread is considered low.
Close analysis of the epidemiological situation and further characterization of the most recent viruses are critical to assess associated risk and to adjust risk management measures in a timely manner.
WHO advises that travellers to countries with known outbreaks of avian influenza should avoid, if possible, poultry farms, contact with animals in live poultry 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, and 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 in 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 influenza-like illness (ILI) and to carefully review any unusual patterns, ensure reporting of human infections under the IHR 2005, and continue national health preparedness actions.