Health officials are assessing the threat of H5N1

The highly pathogenic H5N1 avian influenza virus (HPAI H5N1) remains a low risk to the general public, and public health experts in the United States believe that available treatments and vaccines, as well as those in development, are sufficient to prevent serious illness to prevent. However, the National Institutes of Health (NIH) and its federal partners remain focused on monitoring the virus and evaluating changes, according to leading officials at the National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH.

In one commentary published in the New England Journal of MedicineNIAID Director Jeanne M. Marrazzo, MD, MPH, and Michael G. Ison, MD, MS, chief of the Respiratory Diseases Branch of NIAID’s Division of Microbiology and Infectious Diseases, say people must balance heightened vigilance with “business as usual” in relation to HPAI H5N1.

Since 1996, HPAI H5N1 influenza viruses have been circulating in at least 23 countries. In late 2021, HPAI H5N1 spread from Europe to North America, causing sporadic infections among wild birds and poultry farms. In 2022, the virus spread to South America, where it devastated birds and marine mammals. In March 2024, USDA scientists identified HPAI H5N1 in U.S. dairy cows, and the virus subsequently reached herds in 16 states.

According to USDA/APHIS, the virus has been found in dairy herds in three states in the past 30 days. In 2024, the virus has caused 66 confirmed and 7 probable cases of influenza in people in the US and one case in Canada. These human cases are caused by the H5N1 type circulating in birds (D1.1) or the type circulating in dairy cows (B3.13).

Against this background, Drs. Marrazzo and Ison say there are four keys to controlling the current outbreak. The first need is timely, effective collaboration between researchers in human and veterinary medicine, public health, healthcare and professional workers, such as dairy and poultry workers.

This includes cultivating trust not only among numerous entities, but also among people seeking care for worrisome symptoms, including conjunctivitis, the authors write. Fortunately, most cases of HPAI H5N1 in the US so far have been mild and resolved on their own without the need for treatment.

The second key is a focus on the Canadian HPAI H5N1 patient, who developed respiratory failure and required life-saving medical interventions and treatment before recovery. The authors write that the mutations found in the virus in this patient indicate an urgent need for vigilant disease surveillance to identify and assess viral changes to evaluate the risk of person-to-person transmission.

According to them, effective surveillance requires that complete genomic sequence data from animals and humans be made available quickly and easily.

Without information about where and when isolates were collected, the data cannot be phylogenetically linked to other reported sequences, limiting understanding of the spread of the virus, they write. These data would also provide an opportunity for early detection of mutations that could indicate a desire for human respiratory epithelium, which may require only one mutation in the virus.

Third, researchers must continue to develop and test medical countermeasures – such as vaccines and therapies that eliminate or alleviate disease – against H5N1 and other flu viruses. Fortunately, current vaccine candidates neutralize circulating strains, which have so far been susceptible to antiviral drugs that could reduce transmission and disease severity, they write.

Finally, Drs. Marrazzo and Ison encourage people to take precautions to avoid exposure to the virus and minimize the risk of infection. For example, people who work with poultry and cows should use personal protective equipment and educate themselves about occupational hazards when working with birds and mammals, as CDC and USDA have repeatedly recommended.

Ideally, following these four steps will help scientists and public health officials investigating HPAI H5N1 more quickly answer the many remaining questions about how the virus spreads, evolves and affects humans, other mammals and birds.