High Pathogenicity Avian Influenza (HPAI) in Cattle

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, the 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 November 2024, more than 30 species of mammals have been infected with HPAI and this number is likely to increase, as data collected by the World Animal Health Information System (WAHIS) suggests the incidence of HPAI infections in the Northern Hemisphere rise in October and peak in February. 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 current intensive circulation of H5N1 in cattle increases the risk of H5N1 viruses becoming better adapted to mammals, and potentially spilling over to other livestock and humans.  

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 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 among 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. It 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. 

WOAH 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.  

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;   
  • Suspected, 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. 
• Implement preventive and early response measures to break the HPAI transmission cycle among animals. This includes applying movement restrictions of infected livestock holdings until infection has stopped and strict biosecurity measures in all holdings, in particular in milking parlours and employ good production and hygiene practices when handling animal products. Raw milk or raw milk products from HPAI infected cows or exposed to those infected with HPAI should not be used to feed animals 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.