The Poultry Site The Pan American Health Organization (PAHO) reported that avian influenza A(H5N1) continues to circulate in the Americas, with new outbreaks detected in birds, mammals, and sporadic human infections linked to exposure to the virus. Clade 2.3.4.4b—the region’s predominant strain since 2021—continues to drive the activity recorded in recent years.
Recent data indicates that 19 countries and territories have reported 5,136 outbreaks in animals since 2022, according to the epidemiological update released yesterday. Since mid October, 73 additional outbreaks have been recorded, primarily in domestic and wild birds. In 2025, nine countries have confirmed 508 outbreaks in birds, along with thousands of wild bird detections, especially in the United States and Canada.
The geographic spread and high frequency of outbreaks in poultry and wild birds continue to challenge biosecurity and food production across the region.
The update also notes ongoing activity in mammals. Canada and the United States have reported 77 outbreaks in wild and domestic mammals so far this year. Since March 2024, the United States has detected infections in dairy cattle in 18 states, with more than 1,000 herds affected. The detection of the virus in non-avian species—including dairy cattle—underscores the need to consider livestock and wildlife surveillance, according to the context of risk and epidemiological patterns.
PAHO reports that human cases remain rare. Since 2022, the Americas have reported 75 human H5N1 infections, with two deaths. In 2025, three cases occurred in the United States and one in Mexico. Additional zoonotic influenza infections include one human case of A(H5N2) in Mexico and one human case of A(H5N5) in the United States—the latter representing the first A(H5N5) infection reported globally.