Are we cultivating the perfect storm for a human avian influenza pandemic?

Abstract

The emergence of highly pathogenic avian influenza (HPAI) A H5N1 virus in dairy cattle marks a troubling new chapter in the ongoing battle against zoonotic diseases. Since its initial detection in 1955, the H5N1 virus has primarily been associated with poultry, posing significant threats to both animal and human health. However, recent outbreaks in U.S. dairy herds across nine states have revealed an alarming expansion of the virus, with over 190 herds affected as of September 2024. This unprecedented spread in cattle has sparked intense concern among scientists and health officials, especially with reports indicating that up to 20% of dairy products may contain traces of the virus. The implications of the H5N1 virus establishing itself in cattle populations are profound. This potential endemic presence could transform dairy farms into reservoirs of the virus, facilitating its evolution and increasing the risk of human transmission. Mutations enhancing viral replication in mammals have already been identified, including the notorious PB2 E627K mutation linked to increased virulence. Moreover, the detection of the virus in the central nervous system of infected animals, including cats, underscores the broad tissue tropism and severe pathogenic potential of the H5N1 virus. Current containment efforts include stringent biosecurity measures and financial incentives for enhanced testing and personal protective equipment (PPE) for farmers. Yet, gaps in testing infrastructure and the resurgence of raw milk consumption pose significant challenges. The U.S. Department of Agriculture (USDA) and the Centers for Disease Control and Prevention (CDC) emphasize the critical need for comprehensive testing and pasteurization to mitigate the risk of human infection. As the scientific community races to adapt existing antiviral treatments and develop effective vaccines, the concept of a One Health approach becomes increasingly vital. This holistic strategy calls for coordinated actions across human, animal, and environmental health sectors to preemptively tackle emerging zoonotic threats. Strengthening surveillance, fostering international cooperation, and investing in research are essential steps to prevent the H5N1 virus from igniting the next global health crisis. The current avian influenza outbreak serves as a stark reminder of the delicate balance between human activities and viral evolution. Our collective ability to respond effectively and proactively will determine whether we can avert the perfect storm brewing on the horizon.

Keywords: Dairy cattle; H5N1; HPAI; Pandemic.

Fig. 1

Global timeline of highly pathogenic avian influenza (HPAI) outbreaks and key events. The timeline spans from the late 19th century to the present, highlighting as red dots the first identified human cases of avian influenza in various continents, as well as the evolution of the virus. The graph also tracks the yearly global human cases and deaths associated with H5N1 virus outbreaks. While cases in the current decade are still low, the recent increase in affected people is of concern

Fig. 2

Spatial distribution and temporal progression of affected commercial flocks and cattle herds by state from January 2022 to September 2024. The graph tracks the number of affected herds and flocks across various states, including notable peaks in states such as California, Iowa, Minnesota, and South Dakota. The data highlights the variability of outbreaks over time, with different states showing varying levels of impact. The color-coded bars represent the cummulative number of affected commercial flocks and cattle herds, for each state illustrating the widespread nature of the outbreaks across the United States. Even though spread in herds has begun only recently, the propagation has been faster than for flocks. The spatial distribution of affected farms is very different depending on the type of animals