WHO Says Avian Flu Outbreaks in Animals Pose Risk to Humans

GENEVA, Switzerland — Ongoing outbreaks of a particularly virulent strain of avian influenza have devastated animal populations on five continents and could pose a risk to humans, the World Health Organization said Wednesday.

The WHO issued its “situation analysis” in partnership with the Food and Agriculture Organization of the United Nations and the World Organization for Animal Health.

Though the outbreak of the goose/Guangdong-lineage of H5N1 avian influenza has largely affected animals up to this point, the three organizations are urging countries to work together to save as many animals as possible and protect people.

Avian influenza viruses normally spread among birds, but the increasing number of H5N1 avian influenza detections among mammals — which are biologically closer to humans than birds are — raises concern that the virus might adapt to infect humans more easily, the organizations said. 

In addition, some mammals may act as mixing vessels for influenza viruses, leading to the emergence of new viruses that could be more harmful to animals and humans, they said. 

The goose/Guangdong-lineage of H5N1 avian influenza viruses first emerged in 1996 and have been causing outbreaks in birds since then.

Since 2020, a variant of these viruses belonging to the H5 clade 2.3.4.4b has led to an unprecedented number of deaths in wild birds and poultry in many countries in Africa, Asia and Europe. 

In 2021, the virus spread to North America, and in 2022, to Central and South America. 

Last year, 67 countries on five continents reported H5N1 high pathogenicity avian influenza outbreaks in poultry and wild birds to World Organization for Animal Health, with more than 131 million domestic poultry lost due to death or culling in affected farms and villages. 

In 2023, another 14 countries reported outbreaks, mainly in the Americas, as the disease continues to spread. Several mass death events have been reported in wild birds, caused by influenza A(H5N1) clade 2.3.4.4b viruses. 

Since 2022, 10 countries across three continents have reported outbreaks in mammals to the World Organization for Animal Health.

Both land and sea mammals have been affected, including outbreaks in farmed mink in Spain, seals in the United States, and sea lions in Peru and Chile, with at least 26 species known to have been affected. 

H5N1 viruses have also been detected in domestic animals such as cats and dogs in several countries, with recent detections of H5N1 in cats announced by authorities in Poland.

“There is a recent paradigm change in the ecology and epidemiology of avian influenza which has heightened global concern as the disease spread to new geographical regions and caused unusual wild bird die-offs, and alarming rise in mammalian cases,” said Dr. Gregorio Torres, head of the Science Department at World Organization for Animal Health, in a written statement.

Risk to Humans

Sporadic influenza A(H5N1) clade 2.3.4.4b virus detections in humans have also been reported, but remain very rare, with eight cases reported since December 2021. Infections in humans can cause severe disease with a high mortality rate. 

The human cases detected thus far are mostly linked to close contact with infected birds and contaminated environments. 

“With the information available so far, the virus does not appear to be able to transmit from one person to another easily, but vigilance is needed to identify any evolution in the virus that can change that,” said Dr. Sylvie Briand, director of Epidemic and Pandemic Preparedness and Prevention at the World Health Organization. 

“WHO is working closely with the Food and Agriculture Organization and the World Organization for Animal Health, and laboratory networks to monitor the evolution of these viruses, looking for signals of any change that could be more dangerous to humans,” she continued.

“We encourage all countries to increase their ability to monitor these viruses and to detect any human cases. This is especially important as the virus is now affecting countries with limited prior experience in avian flu surveillance,” she added.

Studies are underway to identify any changes in the virus that may help the virus to spread more easily among mammals, including humans. 

In the meantime, the three partner organizations are urging countries to take the following actions:

Prevent avian influenza at its source through enhanced biosecurity measures in farms and in poultry value chains, and apply good hygiene practices. 

Rapidly detect, report and respond to animal outbreaks as the first line of defense. When an infection is detected in animals, countries are encouraged to implement control strategies as described in World Organization for Animal Health standards.

Strengthen influenza surveillance in animals and humans. Genetic sequencing should be conducted periodically to detect any changes in the viruses already present in the area or the introduction of new viruses. In humans, the following should be prioritized: (i) surveillance for severe acute respiratory infections and influenza-like illnesses, (ii) careful review of any unusual epidemiological patterns, (iii) reporting of human infections under the International Health Regulations, and (iv) sharing of influenza viruses with WHO Global Influenza Surveillance and Response System Collaborating Centers for Reference and Research on Influenza. 

Conduct epidemiological and virological investigations around animal outbreaks and human infections. 

Share the genetic sequence data of viruses from humans, animals or their environments in publicly accessible databases rapidly, even before peer-reviewed publication.

Encourage collaboration between the animal and human health sectors, especially in the areas of information sharing, joint risk assessment and response. 

Alert and train health care workers and occupationally exposed persons on ways to protect themselves. 

The general public as well as animal workers should be advised to avoid contact with sick and dead animals, and to report these to animal health authorities. They should also be advised to seek medical care if unwell and to report any exposure to animals to their health care provider.

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