Avian Flu Diary: OFFLU Guidelines for High Pathogenicity Avian Influenza Virus Risk Mitigation in Cattle

#18,905

A little over 18 months ago the assumption was that cattle were not particularly susceptible influenza A viruses in general, and HPAI viruses in particular. Experimental infection with H5N1 had been done in the lab, but it had never been observed to occur naturally.

As a result, when Texas dairy herds began to show signs of illness in early 2024, it took months before anyone bothered to test them for HPAI H5 (see Curious Reports of Unknown Disease In Dairy Cows (Texas, Kansas & New Mexico).

Once it was established that lactating dairy cows could contract HPAI H5N1, we were almost immediately reassured it was a limited event; the result of single spillover of a specific (genotype B3.13) strain, which was geographically limited to North America and unlikely to spread globally.

The May 2024 UK HAIRS Risk Statement On Avian Influenza (H5N1) In Livestock estimated that H5N1 genotype B3.13 presents ` at most, a very low risk' to the UK, citing a low likelihood of the virus being carried across the Atlantic to Europe.

That optimistic assumption was challenged in June of 2024, with a statement from Germany's FLI on the Experimental Infection Of Dairy Cows With European H5N1 Virus, and later by reports of H5N1 antibodies found in Pakistani goats and sheep.

Over the next six months we saw a nearly 10-fold increase in infected dairy herds in the United States (> 1,000), along with isolated spillovers in Alpacas and pigs. We've also seen a growing number of human (n=70), feline, and peridomestic mammal infections in the United States; many linked to cattle or poultry exposure.

Things have picked up even more in 2025, as we've seen another strain (genotype D1.1) spillover into dairy cattle in two states (Nevada & Arizona), and have seen evidence of infection with other strains in both a UK sheep and in sheep in Norway.

Suddenly, the prospect of HPAI spilling over into livestock in other countries has become more plausible.

This past week the animal influenza expert group of the World Organization for Animal Health and the UN Food and Agriculture Organization, known as OFFLU, issued a new - and far more robust - set of recommendations on HPAI mitigation risk in cattle.

This report does comes with a disclaimer: This document provides the point of view of independent OFFLU experts and does not necessarily reflect the position of the parent organisations FAO and WOAH.

Large international organizations such as WOAH and the FAO can sometimes be slower to reach a consensus, having to consider to rival concerns such as trade policies, national sovereignty, or economic impacts.

While acknowledging that they must be tailored to work with varying local resources and production systems, this 11-page document makes sweeping recommendations on a variety of fronts, including:

Implementing risk-based bulk milk surveillance

Enforcing pasteurization and safe disposal of waste milk

Applying flexible movement controls with testing and quarantines

Improved biosecurity & milking practices

Protecting workers with PPE

Due to its length, I've just posted the link and a brief excerpt. Follow the link to read it in its entirety. I'll have a brief postscript when you return.

OFFLU Guidelines for High Pathogenicity Avian Influenza Virus Risk Mitigation in Cattle
October 2025

Lorcan Carnegie1 , Hélène Duault2 , Folorunso Fasina1 , Yuka Moribe3 , Mariana Delgado3 , Gounalan Pavade3 , Gregorio Torres3 , Beatriz Martínez-López4 , Christopher HamiltonWest5 , Laura Roberts6 , Steve Hinchliffe7 , Diann Prosser8 , Nick Lyons1 , Dirk Pfeiffer9,10 and Guillaume Fournié

This OFFLU Applied Epidemiology Technical Activity document provides practical, evidence-based risk mitigation measures to support countries in making informed decisions to curb the spread of HPAIVs into and within cattle populations, and offers a flexible framework that can be adapted to diverse regional contexts.
Using the 2024- onwards A(H5N1) clade 2.3.4.4b outbreak in US dairy cattle as a case study, we first outlined putative risk pathways for virus introduction into farms, transmission within and between herds, and onward spread to other species, including humans. These pathways were then assessed through an extensive literature review to propose intervention strategies, proportionate to the identified risks, and grounded in current scientific evidence.
It is evident that high rates of virus transmission have occurred both within and between US dairy farms, likely influenced by local structural characteristics of the production system, including intensive management practices, large herd sizes, spatial clustering of farms, and substantial inter-farm movement of cattle, workers, and vehicles.

However, the mechanisms of transmission to and within cattle herds are not fully elucidated, representing a key constraint in the development of risk mitigation measures [5,12–14]. While xperimental infections show multiple possible routes, the dominant pathways under field conditions remain unresolved [11,12,15–17].

(Continue . . . )

Another point worth mentioning, while U.S. officials have focused almost entirely on lactating dairy cows (rarely testing steers or bulls), this guidance document acknowledges the jury is still out on HPAI's spread in non-lactating livestock.

They write:

Although current evidence links infection primarily to dairy cattle, limited investigations in beef and non-lactating cattle mean that the susceptibility of these populations, and their potential role in onward transmission remains uncertain.

The shift in tone and depth of this document over what we saw issued in late 2024 is substantial. If WOAH's statement in December of 2024 was a warning (be alert, report cases, pasteurize, etc. ), then today's is an actionable playbook.