WHO

Human infection with avian influenza A(H7N9) virus – China

On 19 June 2017, the National Health and Family Planning Commission of China (NHFPC) notified WHO of five additional laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus in China. On 24 June 2017, the NHFPC notified WHO of 10 additional laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus in China. On 30 June 2017, the NHFPC notified WHO of six additional laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus in China.

Details of the case patients

On 19 June 2017, the NHFPC reported five laboratory-confirmed human cases of infection with avian influenza A(H7N9) virus in China. Onset dates ranged from 25 April to 6 June 2017. Of these five cases, one was female. The median age was 55 years (range 41 to 68 years). The case patients were reported from Beijing (1), Guangxi (1), Guizhou (1), Hunan (1), and Zhejiang (1). At the time of notification, there was one death. Four cases were diagnosed as having severe pneumonia. Three cases were reported to have had exposure to poultry or live poultry market, and two had no known poultry exposure. No case clustering was reported.

On 24 June 2017, the NHFPC reported 10 laboratory-confirmed human cases of infection with avian influenza A(H7N9) virus in China. Onset dates ranged from 5 to 19 June 2017. All cases were male. The median age was 53.5 years (range 31 to 79 years). The cases were reported from Anhui (1), Beijing (2), Guizhou (1), Hebei (1), Inner Mongolia (1), Jiangsu (1), Sichuan (2), and Tianjin (1). This is the first case reported in Inner Mongolia since the virus emerged in 2013 although two cases were recently reported from Shaanxi province but who had likely exposure in Inner Mongolia. At the time of notification, there were two deaths. Eight cases were diagnosed as having either pneumonia (4) or severe pneumonia (4). Nine cases were reported to have had exposure to poultry or live poultry market, and one had no known poultry exposure.

One cluster with two cases was reported and both cases are from Panzhihua City, Sichuan Province, and had exposure to the same live poultry market. The cluster includes:

• A 79-year-old male, who had symptom onset on 12 June 2017 and was admitted to hospital with severe pneumonia on 15 June 2017, then died on the 21 June 2017. He was living on an upper floor of the live poultry market and passed regularly through the market.
• A 48-year-old male, who had symptom onset on 7 June 2017 and was admitted to hospital with severe pneumonia on 11 June 2017. He is a seller of poultry at the same live poultry market.

On 30 June 2017, the NHFPC reported six laboratory-confirmed human cases of infection with avian influenza A(H7N9) virus in China. Onset dates ranged from 11 to 23 June 2017. Three cases were male. The median age was 37.5 years (range 4 to 72 years). The cases were reported from Guizhou (1), Shanxi (1), and Yunnan (4) provinces. At the time of notification no associated deaths were reported. Four cases were diagnosed as having either pneumonia (1) or severe pneumonia (3). Two mild cases, identified through ILI surveillance, were reported: one in a child with exposure to market poultry and one in an adult. Five cases were reported to have had exposure to poultry or live poultry market, and one had no known poultry exposure. These are the first cases reported with exposure to the virus in Yunnan province. Previous cases reported from Yunnan province had likely exposure in a neighbouring province.

One cluster with two cases was reported, which include:

• A 33-year-old female from Wenshan, Yunnan Province had symptom onset on 17 June 2017 and was admitted to hospital with severe pneumonia on the same day. She had no apparent exposure to live poultry.
• Her sister-in-law, a 42-year-old female also from Wenshan, Yunnan Province, visited her in the hospital, developed mild symptoms on 21 June and was hospitalized on 24 June 2017. Investigation of the case revealed that she ran a shop near a live poultry market and bought live poultry from the market on a daily basis before her symptom onset. The investigation concluded that the likely source of her infection was exposure to the virus from visiting live poultry markets.

To date, a total of 1554 laboratory-confirmed human infections with avian influenza A(H7N9) virus have been reported through IHR notification since early 2013.

Public health response

The Chinese government at national and local level is taking preventive measures which include:

• Continuing to guide the provinces to strengthen assessment, and prevention and control measures.
• 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.
• 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) virus and the geographical distribution in the fifth epidemic wave (i.e. onset since 1 October 2016) is greater than earlier waves. This suggests that the virus is spreading, and emphasizes that further intensive surveillance and control measures in both human and animal health sector are crucial.

According to the epidemiological curve, the number of reported cases on a weekly basis seems to have peaked in early February and is slowly decreasing. The peak in cases this year corresponds to the timing of the peak in cases in previous years.

Most human cases 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 cases can be expected. Additional sporadic human cases of avian influenza A(H7N9) in other provinces in China that have not yet reported human cases are also expected. Similarly, sporadic human cases of avian influenza A(H7N9) detected in countries bordering China would not be unexpected. Although small clusters of cases of human infection with avian influenza A(H7N9) virus have been reported including those involving patients in the same ward, current epidemiological and virological 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 advice

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.