PAHO warns of expanding Avian Influenza H5N1 in the Americas

The Pan American Health Organization (PAHO) has issued a regional alert regarding the continued spread of avian influenza A (H5N1) across the Americas.

David Corredor

The Pan American Health Organization (PAHO) has issued a regional alert regarding the continued spread of avian influenza A (H5N1) across the Americas. According to the latest epidemiological update, the virus remains highly active among poultry, wild birds, and even mammals, posing significant challenges to animal health, food security, and public health systems.

• Since 2022, 19 countries and territories have reported 5,136 outbreaks in animals, reflecting the persistent circulation of the H5N1 clade 2.3.4.4b, which has dominated the region since 2021.
• In 2025 alone, nine countries confirmed 508 outbreaks in commercial poultry, alongside thousands of detections in wild birds, particularly in the United States and Canada.
• This surge underscores the virus’s geographic expansion and its impact on biosecurity measures in the poultry industry.

The situation is further complicated by cross-species transmission. Canada and the United States have documented 77 outbreaks in mammals this year, including infections in wildlife and domestic animals. Notably, the U.S. dairy sector has faced ongoing challenges since March 2024, with confirmed infections in 18 states and over 1,000 herds affected. The detection of H5N1 in cattle highlights the urgent need to broaden surveillance beyond avian species to include livestock and wildlife, applying a One Health approach.

• Human infections remain rare but concerning.
• Since 2022, the Americas have reported 75 human cases of H5N1, including two fatalities.
• In 2025, three cases were confirmed in the United States and one in Mexico.
• Additionally, isolated zoonotic infections with other avian influenza strains—H5N2 in Mexico and H5N5 in the U.S.—have been documented, the latter marking the first global case of its kind.
• Most human cases have been linked to direct contact with infected animals, with no evidence of sustained person-to-person transmission.

PAHO emphasizes that properly cooked poultry products do not transmit the virus. However, the organization urges countries to strengthen epidemiological, virological, and genomic surveillance, enforce strict biosecurity protocols in farms, and ensure rapid detection and reporting of new outbreaks. Special attention should be given to high-risk groups such as poultry workers, veterinarians, and those handling wild fauna.

The expanding footprint of H5N1 across avian and mammalian populations signals a critical moment for regional health authorities. Coordinated action is essential to mitigate risks, protect food systems, and prevent potential public health emergencies.