Authors: A. Bouma, H.A. Lim, T.J.D. van Riet, H.I.J. Roest

Since 2021, high pathogenicity of avian influenza virus H5N1 (HPAI H5N1) has spread worldwide.  It is present in many countries, causing widespread infections in poultry that are often controlled through large-scale culling. The virus is also established in wild bird populations and has led to infections in several mammal species. While human infections remain rare, the risk of a broader public health event, such as a pandemic, cannot be ignored. Reducing virus spread is therefore a priority for both animal and human health. Vaccination could be one of the tools to support this goal and should not be hampered by unjustified trade barriers.

Global situation of HPAI

HPAI H5N1 continues to cause recurring outbreaks in poultry and mammals, with often devastating impacts on the poultry sector and wild animal populations. Control measures rely largely on culling infected flocks, leading to the loss of millions of birds. This approach warrants reconsideration, particularly given the sustained circulation of the virus in wild bird populations. More sustainable, long-term strategies are needed, and vaccination could serve as a valuable additional tool to achieve this goal.

Vaccination, animal health and safe trade

In 2023, the WOAH World Assembly of Delegates adopted Resolution No. 28, recognising vaccination as a complementary disease control tool. WOAH international standards stipulate that vaccination use does not affect a country’s HPAI-free status, provided surveillance demonstrates the absence of infection.

Despite this progress, several challenges remain. Vaccination programmes are currently applied in only a limited number of at-risk countries. Although more countries are considering vaccination, concerns about vaccination and surveillance costs, product value and potential impacts on international trade continue to limit uptake, especially in exporting countries. While some trade barriers are justified, others appear disproportionate and need further discussion.

To address these challenges, the Netherlands set up an international working group on HPAI vaccination and trade. Together with Canada, the European Commission, France, the United Kingdom, the United States of America and WOAH, the Netherlands organised a meeting of this working group last January. Participants agreed to work together to make HPAI vaccination feasible in the near future, providing necessary assurances to allow safe trade.  

Key issues to be addressed

The working group underlined the need to develop and recognise minimum requirements that would facilitate international trade in products from vaccinated poultry and eliminate unjustified trade barriers. The group also noted that agreements with respect to vaccination and trade should be aligned with existing international standards, such as zoning, and should include appropriate surveillance and control measures that support virus control while maintaining trade confidence.

Next steps

A side event will be organised during the WOAH General Session in May. The international working group will present progress to date and outline planned activities. The focus will be on improving understanding of vaccination performance and exploring the development of minimum, widely supported surveillance programme requirements to demonstrate the absence of infection and facilitate trade in products from vaccinated poultry.

In addition, WOAH will develop guidelines for surveillance of HPAI in vaccinated poultry population, with the aim of supporting disease status recognition and safe trade.

Members interested in supporting future vaccination efforts are encouraged to express their interest.

Looking ahead

The goal is to move towards a more sustainable poultry sector that prioritises animal health and welfare, while also protecting public health and the environment.

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WOAH has launched the Guidelines Surveillance of High Pathogenicity Avian Influenza for Smallholder Poultry Systems in Resource-Limited Settings, providing Veterinary Authorities and Veterinary Services involved in high pathogenicity avian influenza(HPAI) surveillance, as well as wildlife, environmental and public health services, animal diagnostic laboratories and other One Health partners with practical recommendations to assist in designing surveillance programmes for the detection of HPAI virus in smallholder poultry systems (SHPS), tailored to the needs and contexts of resource-limited settings.

What the Guidelines Contain

The guidelines Section 1 showcases the diversity and complexity of SHPS beyond the value chain and highlights the importance of community participation to address issues associated with poultry health and enhance effective disease surveillance programmes in such settings.

Section 2 outlines the main objectives, target audience and the international framework, standards and existing tools that link to this guidance.

Section 3 provides six practical phases for developing a surveillance programme in a participative manner — from defining objectives and mapping poultry systems to choosing methods, setting up communication and reporting pathways, and evaluating performance.

Section 4 focuses on training, including a training of trainers model to strengthen local capacity.

The Annex contains ready-to-use tools, templates, figures and evaluation indicators to help users apply the guidance in the field.

Why Did WOAH Develop These Guidelines?

Low- and middle-income countries (LMIC) of the world face several challenges in preventing and responding to avian influenza outbreaks, particularly among smallholder (backyard) poultry farmers. Low-sensitivity surveillance systems in SHPS hinder early detection, thereby increasing the spread of the virus. Furthermore, conventional surveillance programmes often demand substantial and ongoing funding while lacking the flexibility to address the full range of disease surveillance needs in SHPS, particularly where resources are constrained.

In the 90th WOAH General Session in May 2023, following the animal health forum and technical item on avian influenza, Resolution No. 28 was adopted that include the recommendation to support poultry keepers, particularly small holders, in implementing correct usage of disease prevention and control tools, such as enhanced biosecurity, early identification of clinical signs and reporting, to prevent the introduction and spread of HPAI. It was identified as a need to provide Members with practical surveillance guidelines targeting small-scale poultry farmers (backyard), tailored to the local socio-economic context.

To this end, WOAH has published these practical guidelines tailored to local contexts, safeguarding farmers’ livelihoods and ensuring the stability of the poultry industry.

How Were the Guidelines Developed?

In 2025, WOAH launched a consultancy to develop these science-based guidelines. They were authored by experts from the Centre for Applied One Health Research and Policy Advice and Agriculture, Fisheries and Conservation Department, Hong Kong and the Institut National de Recherche pour l’agriculture, l’alimentation et l’environnement, France.

In April 2025, the first draft underwent peer review by a WOAH ad hoc Group, which provided expert opinions and recommendations while ensuring diverse and regional perspectives were considered. The WOAH Scientific Commission for Animal Diseases (SCAD) also reviewed the draft to confirm scientific soundness and alignment with WOAH international standards. Following these reviews and revisions, the guidelines were officially published on the WOAH website (English, French, Spanish) in January 2026.

WOAH encourages users of these guidelines to share their implementation experience and to provide constructive feedback through WOAH Delegates or their representatives, so that this publication can be further refined and adapted to the ever-changing ecology of HPAI viruses, food production systems and surveillance tools.

More information

Recording of the launch webinar on 25 February 2026: Launch of Guidelines on Surveillance of HPAI for Smallholder Poultry Systems in Resource-Limited Settings

Contact: Science and Disease Management Department ([email protected])

Recent events highlight the scale and persistence of this threat. The European Food Safety Authority reported exceptionally high HPAI activity in wild birds during Europe’s 2025 autumn migration, with detections quadrupling those reported in 2024 and representing the highest levels observed since 2016. Among the affected species were common cranes (Grus grus), with more than 20,000 deaths recorded in Germany alone. In North America, the virus remains widespread in wild birds and is increasingly detected in a wide range of mammalian species. In the subantarctic islands of South Georgia, new infections are being reported in southern elephant seals (Mirounga leonina), compounding losses of nearly 50% of breeding females since 2023. Similarly, in the neighbouring Falkland Islands (Islas Malvinas), the world’s two largest colonies of black-browed albatrosses (Thalassarche melanophris) experienced recurrent HPAI outbreaks and a marked decline in the number of breeding birds in 2024 and again in 2025. 

These mortality events have far-reaching ecological consequences. Population declines, reproductive failure, and disrupted species interactions can undermine ecosystem stability and species conservation, with potential generational impacts. Continued spillover into mammals also elevates One Health concerns, with potential implications for companion animals, livestock production and human health. 

Reducing further impacts and supporting recovery requires expanded and coordinated wildlife surveillance, rapid genomic characterization of viruses, improved data sharing, integration of broader conservation actions, and addressing other conservation threats such as habitat loss, overfishing, invasive species, pollution, and climate change. 

Innovative approaches such as Nature-based solutions that strengthen ecological resilience and maintain the natural barriers that limit pathogen spillover should be actively explored. Examples of these solutions include supporting natural scavenger populations to enhance biological removal of infected carcasses, restoring and protecting wetlands and coastal habitats to reduce crowding of migratory birds, maintaining heterogeneous freshwater–coastal landscapes that disperse foraging and roosting densities, and minimizing artificial congregation points that can serve as viral hot spots. 

HPAI has become a global conservation and One Health challenge, demanding urgent and sustained cross-sector collaboration to limit ongoing ecological damage. This scale of biodiversity loss will result in profound and unpredictable ecological disruption, including loss of ecosystem services and the breakdown of food-web dynamics. 

Veterinary authorities and wildlife health professionals are instrumental in establishing strategies and coordinating control plans for HPAI that emphasise biosecurity and biosurveillance involving both wild and domestic animals and timely sharing of up to date information on HPAI events.  

The ongoing threat of high pathogenicity avian influenza (HPAI) demands urgent global attention as it transcends its avian origins to affect domestic and wild mammals with increasing frequency. Notably, its ongoing circulation in dairy cattle in the United States of America (USA) is raising concerns within the international community. 

While the virus primarily affects domestic and wild birds, it is increasingly being reported in both terrestrial and aquatic mammals. As of September 2025, around 40 species of mammals have been infected with HPAI. These cases further highlight the virus’s ability to cross species barriers and pose a threat to wildlife, domestic animals, and public health.  

The ongoing detections of HPAI in dairy cattle in the USA, spark significant international concern. Infected cattle are either asymptomatic or with mild illness showing non-specific clinical signs such as decreased milk production, thicker-colostrum‐like milk, reduced appetite, lethargy, fever and dehydration. The continued detection of H5N1 in cattle increases the risk of H5N1 viruses becoming better adapted to mammals, potentially spilling over to other livestock, humans, and regions.  

Investigations so far have identified raw milk from infected cows as a high-risk material. There is evidence of horizontal virus transmission from infected lactating cows to other animals including cows, cats and poultry.  Thus, only milk produced by non-infected cows and that has been pasteurised or has followed a similar virus inactivation process should be commercialised.  

No specific adaptation of the virus to either humans or mammals has been identified. Several studies are being carried out to further explore the pathogenesis and transmission routes of these viruses, including between cattle and from cattle to other animals.  

In collaboration with its Reference Centres, FAO and WHO,  our networks of experts and Members, the World Organisation for Animal Health (WOAH) is closely monitoring
the situation to assess the risks to animals. The risk to humans is currently considered low for the general public and is considered low to moderate, for those exposed to infected birds, animals or contaminated environment. Timely and transparent notification is crucial to maintain a good understanding of the disease situation and prevent any type of misinformation or disinformation. 

In light of the impact on animal and public health, the Scientific Commission for Animal Diseases considered at its February 2025 meeting that ‘infection of bovines (Bos taurus) with influenza A viruses high pathogenicity’ meets the Terrestrial Code glossary definition for ‘emerging disease’. Accordingly, Members are required to notify the occurrence of HPAI in cattle to the World Animal Health Information System (WAHIS) in accordance with the WOAH Terrestrial Code Article 1.1.4.

WOAH also reminds its 183 Members that, based on the information currently available, restrictions to the international trade of healthy cattle and their products are only recommended if justified by an import risk analysis conducted according to the WOAH Terrestrial Animal Health Code Chapter 2.1.  

Finally, WOAH invites Members to consult OFFLU Guidelines for High Pathogenicity Avian Influenza Virus Risk Mitigation in Cattle. These guidelines  provide practical, evidence-based measures to support Members in their efforts to  mitigate the risk of HPAI virus spread in cattle. It outlines key transmission pathways and proposes proportionate intervention strategies based on the latest scientific evidence.

WOAH calls on its Members to: 

• Increase avian influenza surveillance in domestic and wild birds.  
• Enhance surveillance for early detection in cattle population in countries where HPAI is known to be circulating.  
• Include HPAI as a differential diagnosis in non-avian species, including cattle and other livestock populations, with high risk of exposure to HPAI viruses, in particular:  
  • Animals showing clinical signs compatible with avian influenza; 
  • Sick or dead domestic animals near HPAI affected premises;  and 
  • Suspected cases, including apparently healthy animals, that have been exposed to or epidemiologically linked to suspected or confirmed HPAI in birds or cattle (i.e. situated in HPAI high-risk areas or in areas where avian influenza has been confirmed). 
• Notify cases of HPAI in all animal species, including cattle or other unusual hosts, to WOAH through its World Animal Health Information System (WAHIS). Genetic sequences of avian influenza viruses should be shared in publicly available databases. 
• Consider OFFLU ‘Guidelines for High Pathogenicity Avian Influenza Virus Risk Mitigation in Cattle’ .
• Implement preventive and early response measures to break the HPAI transmission cycle among animals. These include applying movement restrictions of infected livestock holdings until infection has stopped and strict biosecurity measures in all holdings, in particular in milking parlours.
• Employ good production and hygiene practices when handling animal products. Raw milk or raw milk products from HPAI infected or exposed cows should not be used for animal feed or for human consumption.  
• Protect humans in close contact with or handling sick cattle or other sick livestock and their products. Exposed humans should always take precautionary measures to avoid getting infected and minimise the risk to mechanically carrying the virus to livestock or companion animals. This should include wearing personal protective equipment, avoiding visiting other livestock premises after the exposure and implementing standard food safety measures when handling animal products from exposed livestock.
• Avoid implementing unjustified trade restrictions. Import risk management measures should be scientifically justified and in line with the WOAH International Standards.

Technical guidelines for the adaptation of diagnostic tests for Influenza A in animals including cattle and other species as well as different types of samples such as milk and nasal swabs are available in the OFFLU website and will be regularly updated.  

WOAH is fully committed to supporting its Members to mitigate the risks associated with avian influenza. We will continue to engage with our networks of experts, OFFLU, as well as public and private partners, notably through the One Health Quadripartite and the Global Framework for Transboundary Animal Diseases (GF-TADs) to provide technical updates as more information becomes available.  

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