Ongoing Avian Influenza Outbreaks in Animals Pose Hazards to Humans, Situation Analysis and Guidance from FAO, WHO, WOAH, 12 July 2023 Statement Geneva/Paris/Rome

Introduction

The prevailing occurrences of avian influenza, commonly known as "bird flu," have inflicted significant devastation on animal populations, encompassing poultry, wild birds, and certain mammals, resulting in detrimental effects on farmers' livelihoods and the food trade. While primarily impacting animals, these outbreaks persistently present risks to human well-being.

In order to safeguard both animals and people, the Food and Agriculture Organization of the United Nations (FAO), the World Health Organization (WHO), and the World Organization for Animal Health (WOAH) are strongly advocating for collaborative efforts among nations across various sectors.

Avian influenza viruses typically disseminate among avian species, but the escalating incidence of H5N1 avian influenza cases in mammals, which are biologically closer to humans than birds, raises concerns about the virus's potential adaptation for easier human transmission. Furthermore, certain mammals may serve as reservoirs for the mixing and emergence of new influenza virus strains, which could prove more harmful to animals and humans alike.

The lineage of H5N1 avian influenza viruses, known as the goose/Guangdong lineage, emerged in 1996 and has been responsible for widespread avian outbreaks since then. Starting from 2020, a variant of these viruses belonging to the H5 clade 2.3.4.4b has caused an unprecedented number of fatalities among wild birds and poultry in numerous countries across Africa, Asia, and Europe. In 2021, the virus spread to North America, followed by Central and South America in 2022.

During 2022, 67 countries spanning five continents reported high-pathogenicity avian influenza outbreaks of H5N1 in poultry and wild birds to WOAH, resulting in the loss of over 131 million domestic poultry due to death or culling in affected farms and communities. In 2023, an additional 14 countries reported outbreaks, primarily concentrated in the Americas, as the disease continues its dissemination. Several incidents of mass bird mortality have been documented, attributed to influenza A(H5N1) clade 2.3.4.4b viruses.

Surveillance of the Recent Surge in Mammalian Outbreaks

Lately, there has been a surge in reports of fatal outbreaks in mammals caused by influenza A(H5) viruses, including A(H5N1). Since 2022, ten countries across three continents have reported such outbreaks to WOAH. It is highly likely that more countries have experienced undetected or unreported outbreaks. Both land and marine mammals have been affected, including outbreaks among farmed minks in Spain, seals in the United States of America, and sea lions in Peru and Chile. At least 26 species have been identified as impacted by the virus. H5N1 viruses have also been detected in domestic animals, such as cats and dogs, in several countries, with recent announcements of H5N1 detections in cats by Polish authorities.

Dr. Gregorio Torres, the Head of the Science Department at WOAH, emphasizes, "There is a recent shift in the ecology and epidemiology of avian influenza, which has raised global concerns due to the disease's expansion into new geographical regions, unusual wild bird die-offs, and a concerning rise in mammalian cases."

Evaluating the Risk to Humans

Occurrences of sporadic influenza A(H5N1) clade 2.3.4.4b virus infections in humans have been reported, but they remain exceedingly rare, with only eight cases reported since December 2021. Infections in humans can result in severe illness with a high fatality rate. Thus far, the identified human cases are predominantly linked to close contact with infected birds and contaminated environments.

Dr. Sylvie Briand, the Director of Epidemic and Pandemic Preparedness and Prevention at WHO, affirms, "Based on the available information, the virus does not appear to possess easy human-to-human transmissibility. However, vigilance is crucial to identify any viral evolution that may alter this scenario." Dr. Briand further states that WHO is closely collaborating with FAO and WOAH, as well as laboratory networks, to monitor viral evolution and detect any changes that could pose greater risks to humans. Countries are strongly encouraged to enhance their virus monitoring capabilities and promptly identify any human cases, particularly in regions with limited prior experience in avian flu surveillance.

Studies are currently underway to identify potential viral changes that may enhance the virus's ability to spread more easily among mammals, including humans.

Keith Sumption, the Chief Veterinary Officer at FAO, underscores the rapidly evolving nature of H5N1's epidemiology, emphasizing the need for vigilance and the timely sharing of genetic sequences for comprehensive risk assessment and effective disease control.

Controlling the Spread of Avian Influenza

Given the unparalleled spread of the A(H5N1) avian influenza virus among avian and mammalian populations, as well as the potential risks to human health, the tripartite partners—FAO, WHO, and WOAH—strongly urge countries to undertake the following measures:

1.     Prevent avian influenza at its source through enhanced biosecurity measures in farms and poultry value chains, accompanied by the implementation of good hygiene practices. WOAH members, in consultation with the poultry sector, should consider poultry vaccination as a complementary disease control measure based on sound surveillance, accounting for local factors such as circulating virus strains, risk assessment, and vaccination implementation conditions.

2.     Rapidly detect, report, and respond to animal outbreaks as the primary line of defense. Upon detecting an infection in animals, countries are encouraged to implement control strategies as outlined in WOAH standards.

3.     Strengthen influenza surveillance in animals and humans. Enhance risk-based surveillance in animals before and during high-risk periods to enable early response. Animal cases of avian influenza should be reported to WOAH promptly. Periodic genetic sequencing should be conducted to identify any changes in already circulating viruses or the introduction of new ones. Prioritized actions for humans include surveillance of severe acute respiratory infections and influenza-like illnesses, vigilant monitoring of unusual epidemiological patterns, reporting human infections under the International Health Regulations, and sharing influenza viruses with WHO Global Influenza Surveillance and Response System (GISRS) Collaborating Centres for Reference and Research on Influenza.

4.     Conduct epidemiological and virological investigations surrounding animal outbreaks and human infections. Surveillance should be intensified to swiftly detect and investigate suspected cases in both animals and humans.

5.     Share genetic sequence data of viruses obtained from humans, animals, or their environments in publicly accessible databases promptly, even prior to peer-reviewed publication.

6.     Foster collaboration between the animal and human health sectors, particularly in the areas of information sharing, joint risk assessment, and coordinated response efforts.

7.     Communicate the risks associated with avian influenza. Raise awareness among healthcare workers and individuals exposed to infected animals regarding protective measures. The general public and animal workers should be advised to avoid contact with sick or deceased animals and promptly report such cases to animal health authorities. Individuals should also seek medical attention if unwell and disclose any potential exposure to animals to their healthcare providers.

8.     Ensure preparedness for an influenza pandemic at all levels.

FAO, WHO, and WOAH continue to convene expert assessments, monitor the rapidly evolving nature of the virus, and update recommendations to curb its spread. These organizations collaborate closely with countries, assisting in preparedness and response efforts while fostering cooperation across nations and sectors. The global spread of the virus to five continents underscores the imperative for global cooperation and vigilance to safeguard animals, people, and economies

Notes to Editors

1.     Various mammalian species known to be infected with A(H5N1) clade 2.3.4.4b viruses include ferret, mink, European otter, North American river otter, marine otter, European badger, skunk, Virginia opossum, Amur leopard, Amur tiger, mountain lion, fisher, European polecat, lynx, bobcat, domestic cat, red fox, coyote, racoon, raccoon dog, South American bush dog, American black bear, brown bear, grizzly bear, Kodiak bear, domestic pig (serology only), grey seal, harbor seal, fur seal, sea lion, porpoise, bottlenose dolphin, short-beaked common dolphin, white-sided dolphin, dogs, Japanese raccoon dogs, Beech marten, Caspian seals, Asiatic black bear, Chilean dolphin, and Burmeister's porpoise. Further studies are required to determine baseline infection levels in wild mammals.

2.     Virological assessment summary

•                Markers for mammalian adaptation:

·       The molecular marker 627K or equivalents, such as 701N, in the PB2 gene have been identified in some, but not all, virus sequences obtained from mammalian infections. These markers are known to enhance viral replication in mammalian cells.

·       Viruses from infected mammals, including humans, do not exhibit changes indicating increased binding specificity to human-like receptors.

·       Viruses from wild birds and poultry indicate no change in their preference for avian-like receptor binding, although certain genetic mutations have been observed that increase their ability to bind to human-like receptors.

·       The virus isolated from infected minks possesses a genetic mutation that could enhance its replication in mammalian cells. Mink and some bird viruses exhibit additional mutations commonly found in human viruses.

•         Antiviral susceptibility:

    ·  Available sequences from human cases do not show markers for resistance to neuraminidase inhibitors (e.g., oseltamivir) or endonuclease inhibitors (e.g.,   baloxavir).

   ·  Sequences analyzed from circulating viruses in animal species only sporadically contain mutations associated with antiviral resistance.

   ·  Based on available information, minimal population immunity against the influenza A(H5) clade 2.3.4.4b virus hemagglutinin is expected in humans.