On Jun. 14, 2024 the Centers for Disease Control and Prevention (CDC) reported data from this study suggested that there is extremely low to no population immunity to clade 2.3.4.4b A(H5N1) viruses in the United States.

To date, there have been 3 human cases associated with an ongoing multistate outbreak of A(H5N1) in U.S. dairy cows. A Based on the information available at this time, CDC’s current A(H5N1) bird flu human health risk assessment for the U.S. general public remains low. All three sporadic cases had direct contact with infected cows. On the animal health side, USDA is reporting that 92 dairy cow herds in 12 U.S. states have confirmed cases of A(H5N1) virus infections in dairy cows as the number of infected herds continues to grow.

The CDC’s CDC’s response to this include finalizing flu serology studies to determine the population immunity among the U.S. general population to the A(H5N1) clade 2.3.3.4b viruses causing outbreaks among animals in the United States.