Highly pathogenic H5N1 avian influenza A virus (HPAI H5N1) continues to pose a low risk to the general public, according to U.S. public health experts. These experts remain confident that current treatments and vaccines, alongside those under development, are sufficient to prevent severe disease. However, the National Institutes of Health (NIH) and its federal partners are keeping a close watch on the virus, assessing potential changes, and focusing on monitoring its spread. This information was highlighted by officials at the National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH.
In a recent commentary published in the New England Journal of Medicine, Dr. Jeanne M. Marrazzo, M.D., M.P.H., NIAID Director, and Dr. Michael G. Ison, M.D., M.S., Chief of the Respiratory Diseases Branch within NIAID’s Division of Microbiology and Infectious Diseases, recommended balancing enhanced vigilance with maintaining everyday activities, such as “business as usual,” regarding HPAI H5N1.
Since 1996, the H5N1 virus has been circulating in at least 23 countries. In late 2021, the virus spread from Europe to North America, resulting in sporadic infections among wild birds and poultry farms. By 2022, it spread to South America, where it devastated bird populations and affected marine mammals. More recently, in March 2024, scientists from the U.S. Department of Agriculture (USDA) identified HPAI H5N1 in U.S. dairy cows, which then reached herds in 16 states. The virus has been detected in dairy herds in three states within the last 30 days, according to USDA/APHIS reports. In 2024, the virus has caused 66 confirmed and 7 probable human cases of influenza in the U.S. and one case in Canada. These human cases have been linked to either the bird strain (D1.1) or the dairy cow strain (B3.13).
In this context, Drs. Marrazzo and Ison emphasize four essential strategies for managing the current outbreak of HPAI H5N1. The first key strategy involves fostering timely, effective collaborations across multiple sectors, including human and veterinary medicine, public health, healthcare, and workers in high-risk occupations such as dairy and poultry farming. This collaboration should not only aim to build trust between these sectors but also with individuals seeking care for symptoms, including conjunctivitis. So far, most U.S. cases of HPAI H5N1 have been mild and have resolved without the need for treatment.
The second key involves examining the case of a Canadian HPAI H5N1 patient who developed respiratory failure and required life-saving intervention before recovering. The mutations identified in the virus from this patient underscore the need for constant disease surveillance to track viral changes and assess potential risks of person-to-person transmission. To enhance this surveillance, Drs. Marrazzo and Ison argue that complete genomic sequencing data from both animals and humans should be made rapidly accessible. Without information about the specific location and timing of virus isolates, the data cannot be linked to other reported sequences, limiting insights into how the virus is spreading.
The third priority is the continued development and testing of medical countermeasures, such as vaccines and therapies that can neutralize or mitigate the disease. Fortunately, current vaccine candidates are effective against the circulating strains of H5N1, and these strains remain susceptible to antivirals, which could reduce transmission and severity of illness.
Finally, the authors encourage individuals to take appropriate precautions to minimize exposure to the virus and reduce the risk of infection. For example, those working with poultry or dairy cows should use personal protective equipment and stay informed about occupational risks, as repeatedly advised by the Centers for Disease Control and Prevention (CDC) and USDA.
By following these four key steps, public health experts believe it will be possible to answer the many remaining questions more efficiently about the spread, evolution, and impact of HPAI H5N1 on humans, mammals, and birds.
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