The H5N1 influenza virus has been identified in 189 dairy cattle herds in 13 states (Texas, Kansas, Michigan, New Mexico, Ohio, Idaho, South Dakota, North Carolina, Colorado, Minnesota, Wyoming, Iowa, and Oklahoma) as of August 8. In addition, the H5 influenza virus has been detected in 14 humans since 2022; 10 cases were linked to exposure in poultry and four cases following exposure to dairy cows. An estimated 230+ people have been tested after exposure to infected animals. Over 4,500 people have been monitored after exposure to infected animals. Nine of the 14 H5 human cases reported in the US have been confirmed as H5N1.

Highly pathogenic avian influenza (HPAI) A(H5) viruses have been detected in U.S. wild aquatic birds, commercial poultry and backyard or hobbyist flocks beginning in January 2022. These are the first detections of HPAI A(H5) viruses in the U.S. since 2016. Preliminary genetic sequencing and RT-PCR testing on some virus specimens shows these viruses are HPAI A(H5N1) viruses from clade 2.3.4.4. As of August 8, 2024, the HPAI A(H5) viruses have been identified in 1,172 outbreaks in 48 states since 2022. Over 100 million U.S. wild aquatic birds, commercial poultry, and backyard or hobbyist flocks have been affected during this outbreak. The HPAI A(H5) viruses have been identified in 9,715 wild birds in 49 states since December 30, 2021.

The FDA announced results from a study to further confirm that pasteurization is effective at inactivating Highly Pathogenic H5N1 Avian Influenza (H5N1 HPAI) virus in fluid milk and other dairy products made from pasteurized milk. The study – the only one to date designed to simulate commercial milk processing – found that the most commonly used pasteurization time and temperature requirements were effective at inactivating the H5N1 HPAI virus in milk. These results complement the FDA’s initial retail sampling study in which all 297 samples of dairy products collected at retail locations were found to be negative for viable H5N1 HPAI virus.

Monitoring and research continue to inform responses to this latest outbreak of H5N1.