Listed Disease

Avian Influenza

With devastating consequences for the poultry industry, farmer’s livelihoods, international trade, and the health of wild birds, avian influenza, also known as ‘bird flu’, has captured the attention of the international community over the years.  

Where outbreaks occur in domestic birds, it is often the policy to cull all poultry, whether infected or healthy, to contain the spread of avian influenza. This represents heavy economic losses for farmers and a long-lasting impact on their livelihoods.  

Migratory wild birds especially waterfowl, are natural reservoir of avian influenza viruses and they play a role in the spread the viruses across large geographical areas and also becomes victims of the disease.

Avian influenza is also a major concern for public health. Whenever avian influenza viruses circulate in poultry, sporadic cases of avian influenza in humans are sometimes identified. 

What is avian influenza?

Avian influenza is a highly contagious viral disease that affects both domestic and wild birds. Avian influenza viruses have also been isolated, although less frequently, from mammalian species, including humans. This complex disease is caused by viruses divided into multiple subtypes (i.e. H5N1, H5N3, H5N8 etc.) whose genetic characteristics rapidly evolve. The disease occurs worldwide but different subtypes are more prevalent in certain regions than others. 

The many strains of avian influenza viruses can generally be classified into two categories according to the severity of the disease in poultry:  

  • low pathogenicity avian influenza (LPAI) that typically causes little or no clinical signs; 
  • high pathogenicity avian influenza (HPAI) that can cause severe clinical signs and possible high mortality rates.

What is bird flu?

In the video below, disease expert, David Swayne breaks down the differences between low and high pathogenicity bird flu, as well as the impacts on farmers and consumers.

Transmission and spread

Several factors can contribute to the spread of avian influenza viruses, such as: 

Movement of infected birds

Farming and sale (live bird markets)

Wild birds and migratory routes.

In birds, avian influenza viruses are shed in the faeces and respiratory secretions. They can all be spread through direct contact with secretions from infected birds, especially through faeces or through contaminated feed and water. Because of the resistant nature of avian influenza viruses, including their ability to survive for long periods when temperatures are low, they can also be carried on farm equipment and spread easily from farm to farm.

In recent years, the changes in the ecology and epidemiology of specific avian influenza lineages led to infection of numerous wild bird species. Consequently, this facilitated the spread of the virus along established migratory routes, resulting in death of many wild birds, including endangered species, and serving as a source for transmission to poultry and wild mammals.

What role do wild birds play in the spread of avian influenza?

Wild birds mostly, wild aquatic birds can be the reservoir for LPAI viruses, and such infections are not associated with disease or mortality in their hosts. Over long periods of time, some of these LPAI viruses have moved into domestic birds (notably galliform poultry) through direct or indirect exposure followed by adaptation and circulation. Some of those viruses have mutated to become HPAI causing severe losses.

Historically, HPAI viruses have not been transferred back into wild aquatic birds, and wild aquatic birds have not had significant involvement in the spread of HPAI to poultry or other domestic birds. In recent years, the epidemiology of HPAI virus has changed, being endemic in domestic birds in a number of countries causing major outbreaks among domestic but also wild birds worldwide.

The global impact of avian influenza

Economic consequences

Avian influenza can kill entire flocks of birds so this causes devastating losses for the farming sector

Dr. Keith Hamilton
Head of the WOAH Preparedness and Resilience Department

Avian influenza outbreaks can have heavy consequences for the poultry industry, the health of wild birds, farmer’s livelihoods as well as international trade. 


might experience a high level of mortality in their flocks, with rates often around 50% 

Job losses

in developing countries can be significant due to the labour intensive nature of the poultry industry

Healthy birds

are often culled to contain outbreaks, resulting in risks to animal and human welfare, protein wastage and economic impacts

The presence of HPAI

restricts international trade in live birds and poultry meat This can heavily impact national economies

Impact on animal health, including wild birds  

With severe mortality rates, avian influenza can heavily impact the health of both poultry and wild birds. Often considered mainly as vectors of the disease, wild birds, including endangered species, are also victims. The consequences of avian influenza on wildlife could potentially lead to a devastating effect on the biodiversity of our ecosystems. 

In addition, avian influenza can also cross the species barrier and infect domestic and wild terrestrial and marine mammals.

Public health risk

The transmission of avian influenza from birds to humans is usually sporadic and happens in a specific context. People who are in close and repeated contact with infected birds or heavily contaminated environments are at risk for acquiring avian influenza.  

However, due to ongoing circulation of various subtypes, outbreaks of avian influenza continue to be a global public health concern.  

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Situation reports

These reports provide an update of the high pathogenicity avian influenza situation at both global and regional levels, according to the information submitted by countries through the World Animal Health Information System (WOAH-WAHIS). 

Cases of avian influenza in mammals

Situation reports on mammals from Members

Avian influenza in cats

Surveillance and reporting of outbreaks

The first line of defense against avian influenza is the early detection. Putting in place accurate warning systems is thus essential to efficiently prevent and control the disease. 

Because of its capacity to rapidly spread across regions, the early detection and timely reporting of cases are key to enable countries to anticipate and get prepared for potential new outbreaks of avian influenza.   

Avian influenza is a WOAH-listed disease. As such, national Veterinary Authorities must report: 

  • Infection with high pathogenicity avian influenza viruses, irrespective of their subtypes, detected in birds (domestic and wild)
  • Infection of birds other than poultry, including wild birds, with influenza A viruses of high pathogenicity
  • Infection of domestic and captive wild birds with low pathogenicity avian influenza viruses having proven natural transmission to humans associated with severe consequences

When LPAI viruses are detected in wild birds, countries can voluntarily report them through the voluntary report on non-WOAH-Listed diseases in wildlife. In addition, countries may self-declare the absence of high pathogenicity avian influenza from their territory on a voluntary basis.  

Avian Influenza prevention

Prevention of avian influenza at its animal source 

Strict biosecurity measures and good hygiene practices are essential to prevent avian influenza outbreaks, because of the resistance of the virus in the environment and its highly contagious nature.

Relevant measures notably include keeping poultry away from contact with wild birds, ensuring good hygiene in poultry housing and equipment and reporting bird illnesses and deaths to the Veterinary Services.

Dr Gounalan Pavade – What can farmers do to stop the spread of bird flu?

Control strategies and compensation for farmers

When an infection is detected in poultry, a policy of culling infected animals and the ones in close contact is normally used in an effort to rapidly contain, control and eradicate the disease.  

Selective elimination of infected poultry, movement restrictions, improved hygiene and biosecurity, and appropriate surveillance should result in a significant decrease of viral contamination of the environment. These measures should be taken whether or not vaccination is part of the overall strategy. 

Systems of financial compensation for farmers and producers who have lost their animals as a result of mandatory culling ordered by national Veterinary Authorities vary around the world; unfortunately, they may not exist at all in some countries. The WOAH encourages its Members to develop and propose compensation schemes because they are a key incentive to support early detection and transparent reporting of animal disease occurrences, including avian influenza. 

The use of vaccination

Under certain specific conditions, vaccination of poultry may be recommended. However, this measure alone should not be considered a sustainable solution to control avian influenza. It must be used as part of a comprehensive disease control strategy, in addition to other health measures. The vaccines used should comply with the standards described in the WOAH Terrestrial Manual. Vaccination will not affect the high pathogenicity avian influenza status of a free country or zone if surveillance supports the absence of infection.

The decision to set up vaccination plans rests with the Veterinary Authority of each country. It must be based on a risk analysis at regional and national level and in consideration of the international context, potential economic consequences of current outbreaks, and the capacity of the Veterinary Services to conduct an effective vaccination campaign. 

Learn More

David Swayne – What role can vaccines play in the fight against bird flu?
David Swayne – Why is the use of vaccination against bird flu still limited today?

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Insights from WOAH’s 90th General Session and Animal Health Forum 

Although WOAH Members have implemented strict preventive and control measures such as movement control, enhanced biosecurity, and stamping out, avian influenza continues to spread. The Animal Health Forum held during WOAH’s 90th General Session convened key stakeholders and the full membership of the Organisation to discuss how to minimise the impacts of avian influenza across sectors. Based on the Technical Item — Strategic Challenges in the Global Control of High Pathogenicity Avian Influenza presented at the event, participants discussed the impact of the disease, the fitness for purpose of existing prevention and control tools, international trade impact, and the necessity to enhance global coordination. Following the Forum, WOAH issued a  policy to action  report capturing the discussions and outcomes. 

Dr Gregorio Torres of the World Organisation for Animal Health describes the main outcomes of the first ever Animal Health Forum dedicated to avian influenza, during WOAH’s 90th General Session.

WOAH Members adopted a Resolution which will serve as a basis for shaping future avian influenza control activities, while protecting wildlife, supporting the poultry industry and the continuity of trade. The Resolution notably underscores the importance of Members respecting and implementing WOAH international standards to effectively combat avian influenza.


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One Health approach

Because of the potential risk on human health and the far-reaching implications of the disease on the health of wild bird populations, avian influenza should be tackled under a One Health approach. Besides the grave impacts of the virus on poultry, avian influenza can also devastate wild birds populations, threatening the sustainability and biodiversity of our ecosystems.

It is therefore critical that the international community work together across sectors to combat the spread of this disease. WOAH is closely working with the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) to monitor the evolution of the disease at the human-animal-environment interface, in line with a One Health approach. 

Elderly man on farmhouse yard embracing few chickens while smiling at camera

OFFLU: WOAH/FAO global network of expertise on animal influenza

Since its launch in 2005, the OFFLU network has continuously worked to reduce the negative impacts of animal influenza viruses, including avian influenza, by promoting effective collaboration between animal health experts and the human health sector.  

The objectives of OFFLU are to: 

More about OFFLU

Professor Ian Brown talks about OFFLU’s main activities, including the gathering and sharing of international data on animal influenza viruses.

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WOAH global scientific network 

Through its global network of more than 300 Reference Laboratories and Collaborating Centres (collectively, ‘Reference Centres‘) the WOAH provides policy advice, strategy design and technical assistance for the diagnosis and control of avian influenza. 

Centres of expertise and standardisation of diagnostic methods, their goal is to provide the required technical and scientific expertise and to form opinions regarding the monitoring, control, and eradication of these viruses. 

They also propose scientific and technical training for Members and coordinate scientific and technical studies in collaboration with other laboratories and organisations. 

The resources on avian influenza found here, developed by WOAH and our partners, are freely accessible and available to everyone for downloading and distribution. 

avian influenza


Find out what you can do to tackle avian influenza 


Learn more with our key publications 


Understanding avian influenza

Learn more about how avian influenza threatens wild birds

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Find out what you can do to tackle avian influenza 

Learn more with our key publications 

On human infections

On wildlife

Epidemiological archives 

Avian influenza Q & A

What is the current situation with avian influenza?

Regular global situation reports are developed by WOAH experts, based on the data reported by countries through the World Animal Health Information System (WAHIS). They are publicly available: 
Consult the latest situation report 
Access WAHIS for latest information 

What are the causes of the current wave of avian influenza cases?

While it is likely that international trade, farming practices and migratory wild birds have contributed to the spread of avian influenza, the current wide range of avian influenza subtypes circulating shows an ever-evolving complexity in both virus genetics and spatiotemporal distribution. This might be explained by multiple reassortments with low pathogenicity viruses circulating in wild birds.

Is avian influenza a seasonal disease?

The dynamic of the spread of avian influenza viruses is complex and difficult to predict. However, the data received by the WOAH over the last 15 years helps to reveal a seasonal pattern: the number of outbreaks of HPAI usually is lowest in September, begins to rise in October, and peaks in February. Several factors can influence this dynamic, such as the wild bird migration pattern, unregulated trade, farming systems, biosecurity and immunity status. 

What factors can facilitate the spread of avian influenza?

At local level, as the avian influenza viruses can survive for long periods in the environment, they can be easily transmitted from farm to farm by the movement of infected animals, as well as contaminated boots, vehicles and equipment if the adequate biosecurity measures are not implemented. During the Northern Hemisphere winter, the wild bird movements may increase, and lower temperatures may facilitate the environmental survival of avian influenza viruses, increasing exposure of infection in poultry. Additionally, the mixing of wild birds from different geographic origins during migration can increase the risk of virus spread and genetic reassortment resulting in changes in viral properties. 

Has the COVID-19 pandemic hindered the implementation of the preventive measures against avian influenza?

Sustaining veterinary activities amid the COVID-19 pandemic is essential in avoiding the detrimental impacts of other diseases, including animal diseases, which could further exacerbate the current health and socio-economic crises. 
Despite the challenging context, Veterinary Authorities in the affected countries have responded to contain AI outbreaks in poultry with control measures, heightened surveillance, and biosecurity recommendations to poultry owners. 

Can avian influenza be transmitted to humans?

The transmission of avian influenza from birds to humans is rare and usually occurs when there is close contact with infected birds or heavily contaminated environments. Indeed, between 2005 and 2020, 246 million poultry died or were culled because of avian influenza. In the same period of time, human have occasionally been infected with subtypes H5N1 (around 850 cases reported), H7N9 (around 1,500 cases reported), H5N6 (around 50 cases reported) and sporadic cases have been reported with subtypes H7N7 and H9N2. 
Following the evolution of the global situation, the WHO Global Influenza programme regularly releases risk assessments on influenzas at the human-animal interface. 
Moreover, there is no evidence to suggest that the consumption of poultry meat or eggs could transmit the AI virus to humans. However, as a general precautionary measure, animals that have been culled as a result of the implementation of control measures in response to an avian influenza outbreak should not enter the human food and animal feed chain. 

What prevention measures are recommended at farm level?

It is essential for poultry farmers to maintain biosecurity practices to prevent the introduction of the virus. Some of these measures include:
– prevent contact between poultry and wild birds
– minimise movements around poultry enclosures
– maintain strict control over access to flocks by vehicles, people and equipment; clean and disinfect animal housing and equipment.
– avoid the introduction of birds of unknown disease status
– report any suspicious case (dead or alive) to the veterinary authorities
– ensure appropriate disposal of manure, litter and dead animals
– vaccinate animals, where appropriate.

Is avian influenza a notifiable disease?

As soon as detected or suspected, avian influenza should be brought to the attention of Veterinary Authorities in accordance with national regulations. In an effort of surveillance and transparency, these authorities are required to timely report of high pathogenicity avian influenza viruses detected in both poultry and non-poultry species including wild birds, and low pathogenicity avian influenza viruses that have proven natural transmission to humans with severe consequences to the World Organisation for Animal Health. In addition, LPAI viruses in wild birds can be reported on a voluntary basis, through the voluntary report on non WOAH-Listed diseases in wildlife. 
Notifying the disease occurrences helps to better monitor, understand and control it. 

What is the World Organisation for Animal Health (WOAH) doing to tackle avian influenza?

To support countries in the fight against this disease, WOAH developed international standards on avian influenza, which provide the framework for the implementation of effective surveillance and control measures.  
 As part of the OFFLU network (WOAH/FAO) of experts on animal influenzas, WOAH and its partners work together to assess the risks of avian influenza viruses and provide the needed guidance and recommendations to the international community. 
Additionally, the World Animal Health Information System (WAHIS) provides a window on the disease situation worldwide. Through its online platform, the system disseminates information about avian influenza outbreaks and sends alerts on events in real time. This allows the international community to follow the evolution of the virus and, therefore, to implement appropriate and timely responses. 

Avian influenza in cats

What is avian influenza and how does it spread? 

Avian influenza, also known as bird flu, is a highly contagious viral disease that affects domestic and wild birds. The disease has also been detected, on rare occasions, in mammals, including humans. Beyond its impacts on animal health, the disease has devastating effects on the poultry industry, threatening workers’ livelihoods, food security and international trade.  

Avian influenza can easily spread through:
– secretions and excretions from infected birds, especially faeces 
– contaminated feed and water (in farms or live birds market) 
– contact with contaminated footwear, vehicles and equipment 
– cross-border movements of birds, including wild birds migration and illegal trade 

Avian influenza viruses are classified into subtypes based on two surface proteins, the hemagglutinin (HA) and neuraminidase (NA). For example, a virus that has HA 7 protein and NA 9 protein is designated as subtype H7N9. At least 16 hemagglutinins (H1 to H16), and 9 neuraminidases (N1 to N9) subtypes have been found in viruses from birds, while two additional HA and NA types have been identified only in bats. 

Can cats catch avian influenza?  

While it primarily affects poultry and wild birds, avian influenza can occasionally be transmitted to mammals, including cats. Cats are unusual hosts of avian influenza. 

How do cats catch avian influenza?  

Exposure to infected wild birds or poultry, or associated food products, are modes of infection for cats. However, further studies are required to increase our understanding of this question. 

What are the symptoms of avian influenza in cats?  

When infected, cats can show a range of clinical signs, including listlessness, loss of appetite, severe depression, fever, dyspnoea (difficulty breathing), neurological disease, respiratory and enteric signs, jaundice, and death. These signs are expected to develop within a few days of exposure to the virus. As with many viral infections, some cats may only show mild signs. 

Can cats die from avian influenza? 

Yes, some cats have died from avian influenza. 
The severity of the disease in cats can vary widely depending on the specific strain of avian influenza involved and the individual cat’s health and immune status. Some infected cats may only show mild symptoms or even be asymptomatic, while others can develop severe respiratory distress and other complications that may lead to death.

What is the difference between influenza infection and cat flu in cats? 

‘Cat flu’ is a common term used to describe disease in cats characterized by signs like a common cold in humans (e.g., runny eyes, sore mouth or throat, dribbling, sneezing, fever). It can be caused by various viruses (calicivirus, herpes virus) or bacteria (bordetella bronchiseptica, chlamydia felis). Vaccines to ‘cat flu’ are commonly available from veterinarians; they provide protection, but they are not 100% effective.  
On the other hand, influenza infection in cats is not the same as cat flu – it relates to an infection of a cat with an influenza virus. No commercially available influenza vaccines are available for cats. 

Can cats be infected with influenza viruses other than avian influenza? 

Cats have been known to be infected with several other subtypes and strains of influenza viruses. Usually, infection is subclinical or only causes mild disease. However, the severity of disease may be exacerbated by stress or other chronic illness. Factors that determine species susceptibility to different influenza viruses are not well understood and require further research. 

Can cats give avian influenza to humans? 

Cats are not significant epidemiological vectors of avian influenza to humans or other animals. While it’s unlikely that people would catch avian influenza through contact with an infected wild, stray, feral, or domestic cat, it is possible—especially if there is prolonged and unprotected exposure to an infected animal. Precautions should be taken when handling a sick animal, whether it is a beloved pet or a wild animal. 

What is the risk of avian influenza being transmitted from a sick cat to a human?  

The risk of transmission of avian influenza from a sick cat to a human is currently very low or negligible.  

What precautions should be taken for suspected cases of avian influenza in cats? 

 – Suspected cases of avian influenza in cats should be isolated from other pets, and individuals handling them should wear appropriate personal protective equipment (PPE). 
– Contact your veterinarian if you suspect your cat is unwell and has been exposed to avian influenza. 
– If you experience flu-like symptoms, consult a doctor. 

What precautions can be taken to avoid exposing cats to avian influenza?

– Where possible avoid direct contact with sick poultry, fallen wild birds, objects with traces of bird droppings, or surfaces or water sources (e.g.: ponds, troughs, lakes) that might be contaminated with saliva, feces, or bodily fluids from birds.  
– Upon returning home, ensure that your shoes are kept out of reach of cats. 
– After coming home from outdoor areas that may have bird droppings, clean your shoes. 
– Disinfect the surface where you placed your shoes. 
– Follow regular hygiene practices, such as washing hands with warm water and soap, particularly after returning home and before handling food. 
– Maintain hygienic conditions while preparing meals for cats. Avoid feeding cats raw poultry meat, particularly if avian influenza outbreaks are reported in the region. 
– Stay informed about the latest announcements from your local authorities. The risk of cats being exposed to avian influenza will be greater if avian influenza is reported in your area. 

What is WOAH doing in this case?  

WOAH is monitoring this event very closely with its Members and scientific network. WOAH is also working with other international Organisations to assess the risk of this event to other animals and for public health.

The Organisation strongly encourages its Members to monitor the occurrence of avian influenza in animals other than birds and to timely inform WOAH through its information system WAHIS.