Human infection with avian influenza A(H7N9) virus – China
On 18, 25 August and 4 September 2017, the National Health and Family Planning Commission of China (NHFPC) notified WHO of four additional laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus in China.
Details of the case-patients
On 18 August 2017, the NHFPC reported one laboratory-confirmed human case of infection with avian influenza A(H7N9) virus in China. The case-patient was a 47-year-old male from Hunan province who developed symptoms on 9 August 2017 and was admitted to hospital on 12 August 2017. He passed away on 13 August 2017. He was reported to have had exposure to live poultry markets.
On 25 August 2017, the NHFPC reported two laboratory-confirmed human cases of infection with avian influenza A(H7N9) virus in China. The two case-patients were both from Xinjiang Uyghur Autonomous Region. The first case-patient was a 73-year-old male with symptom onset on 7 August 2017 and was admitted to hospital with severe pneumonia on 14 August 2017. He had exposure to live poultry markets. The second case-patient was a 74-year-old male with symptom onset also on 7 August 2017 and admitted to hospital with severe pneumonia on 12 August 2017. He had no exposure to live poultry. Both cases were in severe condition at the time of reporting. Although these two cases are reported from the same region, they live in different communities, and there is no known epidemiologic link between the cases.
On 4 September 2017, the NHFPC reported one laboratory-confirmed case of infection with avian influenza A(H7N9) virus in China. The case-patient was a 58-year-old male from Jiangsu province. He developed symptoms on 9 August 2017, was admitted to hospital on 14 August 2017, and passed away on 25 August 2017. He was reported to have had exposure to live poultry markets.
To date, a total of 1562 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 assessment is that although newly infected human cases of avian influenza A(H7N9) have been reported less frequently in recent weeks, it is still likely that sporadic cases will continue to occur in China taking into consideration the previous epidemic situation and recent patterns.
Thus the government at national and local level continue to take preventive measures which include:
- Continuing to guide the provinces to strengthen assessment, and prevention and control measures.
- Guiding the provinces to make use of the present low-incidence period to review the prevention and control efforts taken to facilitate implementation of long-term measures.
- Continuing to carry out risk communication and issue information notices to provide the public with guidance on self-protection.
The government has cautioned provinces that infection prevention and control cannot be treated lightly, and that they should stay alert to ensure that cases can be identified and managed in a timely and effective manner.
WHO risk assessment
As seen in previous years the number of weekly reported cases has decreased over the summer months. 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) however has been greater than earlier waves. This suggests that the virus has spread, and emphasizes that further intensive surveillance and control measures in both the human and animal health sector remain crucial.
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 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 advises that travellers to countries with known outbreaks of avian influenza should, if possible avoid 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 food hygiene practices.
WHO does not advise special screening at points of entry, nor does it currently recommend any travel or trade restrictions, with regard to this event. 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.