Description of the situation
On 6 January 2022, the International Health Regulations (IHR) Focal Point of the United Kingdom of Great Britain and Northern Ireland notified WHO of the detection of a laboratory confirmed human case of avian influenza A(H5) from South West England.
The case lived with a large number of domestically kept birds which had onset of illness on 18 December 2021, and subsequently tested positive with Highly Pathogenic Avian Influenza (HPAI) A(H5N1) by the United Kingdom National Reference Laboratory at the Animal and Plant Health Agency (APHA) Weybridge laboratory. As part of routine follow up of exposed persons to avian influenza cases, an upper respiratory swab was taken from the case on 24 December 2021 which tested positive for influenza A with subtyping H5. Further characterization of the virus is ongoing. This result was reproduced on two successive upper respiratory swabs collected during the following days. The case has remained clinically asymptomatic and is now considered to not be infectious.
Following successful virus isolation from samples collected from birds on the infected premises, APHA analyzed full genome sequence data for the HPAI A(H5N1) virus present in these birds. Genomic analysis demonstrated that the sequence generated contained no strong correlates for specific increased affinity for humans.
Public health response
All contacts have been identified and managed according to the national public health protocols. None of the contacts have reported symptoms and no evidence of secondary transmission has been identified to date.
The infected premises were visited by APHA personnel who completed culling of all the birds. Several measures including complete decontamination and cleaning of the outside of the property have been completed.
A three-kilometer captive bird (monitoring) controlled zone was declared by the Department for Environment, Food and Rural Affairs around the infected premises. The zone will remain in place for at least 21 days following the completion of preliminary cleansing and disinfection and will not be lifted until surveillance activities including clinical inspections of all commercial premises in the zone have been undertaken.
WHO risk assessment
Since 2003, a total of 863 cases and 455 deaths of influenza A(H5N1) human infection have been reported worldwide, including this case in the United Kingdom. The most recently reported case in humans prior to the current case, was in October 2020 in Lao People's Democratic Republic in a one-year-old female who had exposure to backyard poultry (for more details, please see the Disease Outbreak News published on 17 November 2020).
Since 1 October 2021, there have been 73 poultry cases and 471 detections in individual wild birds of Highly Pathogenic Avian Influenza A(H5N1)
This is the first reported case of human infection of influenza A(H5) infection in the United Kingdom. The case remained clinically asymptomatic. The virus has not been detected beyond this single case. Public health measures from both the human and animal health agencies have been implemented. Based on available information, WHO assesses the risk to the general population posed by this virus to be low and for occupationally exposed persons it is considered to be low-to-moderate.
There are no specific vaccines for preventing Influenza A(H5N1) in humans. Candidate vaccines to prevent H5 infection in humans have been developed for pandemic preparedness purposes. Close analysis of the epidemiological situation, further characterization of the most recent viruses (human and poultry) and serological investigations are critical to assess associated risk and to adjust risk management measures in a timely manner.
WHO advice
This case does not change the current WHO recommendations on public health measures and surveillance of influenza.
Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of global surveillance to detect and monitor virological, epidemiological and clinical changes associated with emerging or circulating influenza viruses that may affect human (or animal) health with timely sharing of such viruses and related information for risk assessment.
All human infections caused by a novel influenza subtype are notifiable under the International Health Regulations (IHR) and 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 (for more details, please see Case definitions for the four diseases requiring notification in all circumstances under the International Health Regulations (2005)).
In the case of a confirmed or suspected human infection caused by a novel influenza virus with pandemic potential, including a variant virus, a thorough epidemiological investigation (even while awaiting the confirmatory laboratory results) of history of exposure to animals, of travel, and contact tracing should be conducted. The epidemiological investigation should include early identification of unusual respiratory events that could signal person-to-person transmission of the novel virus and clinical samples collected from the time and place that the case occurred should be tested and sent to a WHO Collaboration Center for further characterization.
When avian influenza viruses are circulating in an area, people involved in specific high-risk activities such as sampling sick birds, culling and disposing of infected birds, eggs, litters and cleaning of contaminated premises should be trained on the proper use of and provided with appropriate personal protective equipment. All persons involved in these activities should be registered and monitored closely by local health authorities for seven days following the last day of contact with poultry or their environments.
Travelers to countries with known outbreaks of animal influenza should avoid farms, contact with animals in live animal markets, entering areas where animals may be slaughtered, or contact with any surfaces that appear to be contaminated with animal feces. Travelers should wash their hands often with soap and water. Travelers should also follow good food safety and good food hygiene practices. 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 as this virus has not acquired the ability to transmit easily among humans.
WHO does not recommend any restriction on travel and/or trade with the United Kingdom based on the currently available information.
Further information
- Current technical information for influenza (avian and other zoonotic) can be found at the WHO website: https://www.who.int/health-topics/influenza-avian-and-other-zoonotic#tab=tab_1
- WHO. Influenza virus infections in humans October 2018. Available at: https://www.who.int/influenza/human_animal_interface/virology_laboratories_and_vaccines/influenza_virus_infections_humans_Oct_18.pdf
- Manual for the laboratory diagnosis and virological surveillance of influenza (2011). Available at: https://apps.who.int/iris/bitstream/handle/10665/44518/9789241548090_eng.pdf
- Terms of Reference for National Influenza Centers of the Global Influenza Surveillance and Response System. Available at: https://www.who.int/influenza/gisrs_laboratory/national_influenza_centres/tor_nic.pdf
- World Organisation for animal health (OIE). Avian influenza. Available at: https://www.oie.int/en/disease/avian-influenza/ Case definitions for diseases requiring notification under the IHR (2005). Available at: www.who.int/ihr/Case_Definitions.pdf
- IHR (2005). Available at: http://www.who.int/ihr/publications/9789241596664/en/