Human Infection With Avian Influenza A(H10N3) – China

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Human infection with avian influenza A(H10N3) – China 10 June 2021

Description of the situation

On 31 May 2021, the National Health Commission of the People’s Republic of China notified WHO of one confirmed case of human infection with avian influenza A(H10N3) virus. This is the first case of human infection with avian influenza A(H10N3) virus reported globally. The case is a 41-year-old male from Zhenjiang City, Jiangsu Province. He developed fever and nausea on 23 April 2021 and was admitted to the intensive care unit of a local hospital on 28 April 2021. The case is currently in a stable condition. The National Influenza Center of the Chinese Center for Disease Control and Prevention, a WHO Collaborating Centre for Reference and Research on Influenza, completed genetic sequencing and analysis of the specimen and confirmed the detection of an influenza A(H10N3) virus of avian origin.

The case had no clear history of exposure to poultry prior to illness onset, based on epidemiological investigation. No avian influenza A(H10N3) virus has been found in the local surroundings or poultry. Close contacts of the case have not shown any symptoms. Based on the local and national assessment, the case was considered to be an incidental infection from avian to human transmission, with a low likelihood of human-to-human transmission.

Public health response

The Chinese government has taken the following monitoring, prevention and control measures:

• Further epidemiological investigation on the origin of infection of the case;
• Strengthened surveillance, including enhanced monitoring of febrile cases, and disinfection of the surrounding environment, including of the case’s residence;
• Close contact tracing and management; and
• Public risk communication activities to heighten public awareness and adoption of self-protection measures.

WHO risk assessment

This is the first human infection with avian influenza A(H10N3) to be detected. Previously, Australia and Egypt detected human infections with influenza A(H10N7), and China reported three human infections with avian influenza A(H10N8) in late 2013 and early 2014. Targeted surveillance projects have detected avian influenza A(H10N3) viruses in birds, however the extent of circulation and epidemiology of this virus in birds is unclear. Further genetic and antigenic characterization are ongoing to determine if this virus is different from previously detected avian influenza A(H10Nx) viruses.

Most previously reported human infections with avian influenza viruses were due to exposure to infected poultry or contaminated environments. Since avian influenza viruses, including A(H10Nx) viruses, continue to be detected in poultry populations, further sporadic human cases could be detected in the future. Currently available epidemiologic information suggests that avian influenza A(H10Nx) viruses have not acquired the ability of sustained human-to-human transmission, thus the likelihood of spread among humans is low. Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. If this were to occur, further community level spread is considered unlikely. The risk assessment will be reviewed as necessary, should further epidemiological or virological information become available.

WHO advice

The detection of this case does not change current WHO recommendations on public health measures and surveillance of influenza. The public should avoid contact with high-risk environments such as live animal markets/farms and live poultry, or surfaces that might be contaminated by poultry or bird faeces. Hand hygiene with frequent washing or use of alcohol-based hand sanitizer is recommended. WHO does not recommend any specific measures for travelers, and advises against the application of any travel or trade restrictions in relation to this event based on the currently available information.

Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of global surveillance to detect virological, epidemiological and clinical changes associated with circulating influenza viruses that may affect human or animal health and timely virus sharing for risk assessment.

All human infections caused by a new subtype of influenza virus are notifiable under the International Health Regulations (IHR, 2005). State Parties to the IHR (2005) are required to immediately notify WHO of any laboratory-confirmed case of a recent human infection caused by an influenza A virus with the potential to cause a pandemic. Evidence of illness is not required for this report. Thorough investigation of every human infection is essential.

Further information

• WHO Avian and other zoonotic influenza
• WHO Monthly Risk Assessment Summary: Influenza at the human-animal interface
• WHO Regional Office for the Western Pacific Avian Influenza Weekly Update
• Protocol to investigate non-seasonal influenza and other emerging acute respiratory diseases
• Maintaining surveillance of influenza and monitoring SARS-CoV-2 – adapting Global Influenza Surveillance and Response System (GISRS) and sentinel systems during the COVID-19 pandemic
• Case definitions for the four diseases requiring notification in all circumstances under the International Health Regulations (2005)