The current outbreaks of avian influenza, commonly known as “bird flu,” have inflicted devastation upon animal populations, including poultry, wild birds, and certain mammals, leading to severe repercussions for farmers’ livelihoods and the food trade. While primarily affecting animals, these outbreaks continue to pose persistent risks to human health.

The Food and Agriculture Organization of the United Nations (FAO), the World Health Organization (WHO), and the World Organisation for Animal Health (WOAH) have united in urging countries to collaborate across sectors in order to save as many animals as possible and safeguard human populations.

Although avian influenza viruses typically transmit among birds, the growing number of H5N1 avian influenza detections among mammals, which share closer biological proximity to humans than birds do, has raised concerns that the virus may adapt more easily to infect humans. Furthermore, some mammals can serve as mixing vessels for influenza viruses, potentially giving rise to new, more harmful strains that affect both animals and humans.

The H5N1 avian influenza viruses, stemming from the goose/Guangdong lineage, initially surfaced in 1996 and have caused outbreaks in birds ever since. Since 2020, a variant of these viruses belonging to the H5 clade 2.3.4.4b has triggered an unprecedented number of deaths in wild birds and poultry across multiple countries in Africa, Asia, and Europe. In 2021, the virus spread to North America, and in 2022, it reached Central and South America.

In 2022, WOAH received reports of H5N1 high pathogenicity avian influenza outbreaks in poultry and wild birds from 67 countries across five continents, resulting in over 131 million domestic poultry losses due to death or culling in affected farms and villages. As the disease continues to spread, another 14 countries have reported outbreaks in 2023, primarily in the Americas. Notably, mass death events in wild birds caused by influenza A(H5N1) clade 2.3.4.4b viruses have been recorded.

Monitoring the recent surge in outbreaks among mammals reveals an alarming trend. Since 2022, ten countries across three continents have reported deadly outbreaks caused by influenza A(H5) viruses, including A(H5N1), in mammals. It is likely that more countries have experienced outbreaks that have yet to be detected or reported. Both land and sea mammals have been affected, with outbreaks observed in farmed mink in Spain, seals in the United States of America, and sea lions in Peru and Chile. At least 26 species have been known to be affected. Additionally, H5N1 viruses have been detected in domestic animals such as cats and dogs in several countries, with recent announcements of H5N1 detections in cats made by Polish authorities.

Dr. Gregorio Torres, Head of the Science Department at WOAH, warns of a recent shift in the ecology and epidemiology of avian influenza, heightening global concern as the disease expands to new geographical regions, triggers unusual wild bird die-offs, and causes an alarming rise in mammalian cases.

Assessing the risk to humans, sporadic cases of influenza A(H5N1) clade 2.3.4.4b virus infections have been reported but remain exceptionally rare, with only eight cases reported since December 2021. Human infections can result in severe illness with high mortality rates. The detected human cases have predominantly been linked to close contact with infected birds and contaminated environments.

Dr. Sylvie Briand, Director of Epidemic and Pandemic Preparedness and Prevention at WHO, states that based on the available information, the virus does not currently appear to transmit easily from person to person. However, she emphasizes the need for vigilance in identifying any changes in the virus that could alter its transmissibility. WHO, in collaboration with FAO and WOAH, is actively monitoring the virus’s evolution and calling on countries to enhance their monitoring capabilities, particularly in regions with limited experience in avian flu surveillance.

Ongoing studies aim to identify any genetic changes in the virus that might facilitate its spread among mammals, including humans.

Keith Sumption, Chief Veterinary Officer at FAO, highlights the rapidly evolving epidemiology of H5N1 and emphasizes the need for vigilance, timely sharing of genetic sequences, and monitoring of the virus’s molecular epidemiology for effective risk assessment and disease control.

To curb the spread of avian influenza, the tripartite partners—FAO, WHO, and WOAH—urge countries to undertake the following actions:

• Implement enhanced biosecurity measures and good hygiene practices in farms and poultry value chains to prevent avian influenza at its source.
• Rapidly detect, report, and respond to animal outbreaks as the first line of defense, implementing control strategies outlined in WOAH standards.
• Strengthen influenza surveillance in animals and humans, with a focus on risk-based surveillance in animals during high-risk periods. Animal cases of avian influenza should be reported promptly to WOAH. Genetic sequencing should be conducted periodically to detect any changes in existing viruses or the introduction of new ones. In humans, surveillance for severe acute respiratory infections and influenza-like illnesses should be prioritized, alongside careful examination of any unusual epidemiological patterns. Human infections should be reported under the International Health Regulations, and influenza viruses should be shared with WHO Global Influenza Surveillance and Response System (GISRS) Collaborating Centres for Reference and Research on Influenza.
• Conduct epidemiological and virological investigations surrounding animal outbreaks and human infections, enhancing surveillance to rapidly detect and investigate suspected cases.
• Rapidly share genetic sequence data of viruses from humans, animals, or their environments in publicly accessible databases, even before peer-reviewed publication.
• Promote collaboration between the animal and human health sectors, particularly in information sharing, joint risk assessment, and response.
• Communicate the risk effectively, providing alertness and training to healthcare workers and occupationally-exposed individuals on protective measures. The general public and animal workers should be advised to avoid contact with sick and dead animals and report such incidents to animal health authorities. If unwell, individuals should seek medical care and report any animal exposures to their healthcare providers.
• Ensure influenza pandemic preparedness at all levels.

FAO, WHO, and WOAH have convened experts to review the situation, monitor the rapidly evolving virus, and update recommendations for controlling its spread. They continue to work with countries on preparedness and response, fostering collaboration across nations and sectors. The global spread of the virus underscores the critical need for global cooperation and vigilance in protecting animals, people, and economies.