H5N1 Avian Flu: Recent Outbreaks and Biosecurity Measures

Highly pathogenic avian influenza (HPAI) H5N1 continues to pose a significant threat to poultry, animal health, and global economies. Recent outbreaks in wild birds, domestic poultry, and even mammals, including dairy cattle, are raising concerns among public health officials and prompting increased biosecurity measures. This article provides an overview of the current situation, recent developments, and essential resources for prevention and control.

Recent H5N1 Outbreaks

Wild Bird Transmission

Intensive transmission in wild, migratory birds is driving the rapid geographic dissemination of H5N1. Research indicates that approximately nine introductions into the Atlantic and Pacific Flyways have fueled the North American panzootic, with Anseriformes (waterfowl) playing a primary role in transmission [1]. Other species can act as dead-end hosts.

Dairy Cattle Infections

In early 2026, H5N1 was detected in dairy cows, marking a spillover event. The USDA Animal and Plant Health Inspection Service (APHIS) identified the D1.1 genotype in Nevada dairy cows, a different genotype than the B3.13 genotype previously implicated in dairy outbreaks [2]. The D1.1 genotype has been linked to some human illnesses, including severe cases.

Human Case in Nevada

Nevada reported its first human case of H5N1 in March 2026, involving a dairy worker exposed to sick cows in Churchill County. The individual experienced only conjunctivitis and is recovering. Close contacts are being monitored, and no human-to-human transmission has been reported [2]. Individuals working with poultry or cows, or with recreational exposure to them, are considered at higher risk.

Northern Ireland Outbreak

In early March 2026, Highly Pathogenic Avian Influenza H5N1 was confirmed at a commercial poultry premises near Omagh, Northern Ireland. Temporary Control Zones (TCZs) were initially established, but have been replaced with 3km Protection Zones (PZs) and 10km Surveillance Zones (SZs) around each infected premises, effective March 11, 2026.

Biosecurity Measures

Given the ongoing threat, strict biosecurity measures are crucial to protect poultry and prevent further spread. These measures include:

• Limiting contact between domestic poultry and wild birds.
• Implementing strict hygiene protocols for personnel and equipment.
• Regular monitoring of poultry flocks for signs of illness.
• Reporting suspected cases to animal health authorities immediately.

Resources

• Ohio Department of Agriculture – HPAI Information
• DAERA (Northern Ireland) – Biosecurity Information

Key Takeaways

• H5N1 avian influenza remains a significant global health threat.
• Wild birds are key drivers of H5N1 spread.
• Spillover events to mammals, including dairy cattle, are occurring.
• Strict biosecurity measures are essential for prevention and control.