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U.S. states and territories varied widely in their capacity to monitor people exposed to the H5N1 avian influenza virus, and in how they would recommend use of antivirals and the H5N1 vaccine, according to a joint survey from the CDC and the Council of State and Territorial Epidemiologists.

Although 89% of the 55 state and territorial jurisdictions surveyed reported the capacity to identify H5N1 virus in humans, 66% of the 50 jurisdictions who reported monitoring H5N1-exposed persons pointed to barriers in monitoring, including personnel shortages, funding, and a lack of other resources, reported Noah Kojima, MD, of the CDC, and colleagues in a research letter in .

Moreover, while 49 of the 50 jurisdictions reported that they had the capacity to test for H5N1, only 59% reported testing respiratory samples from symptomatic patients.

Of the 50 health authorities who responded, just 38% said they would recommend empirical antiviral treatment before testing for H5N1 in exposed, symptomatic people, and 33% said they would recommend antiviral post-exposure prophylaxis for close contacts of people with laboratory-confirmed H5N1.

These responses are not in line with , which state that (Tamiflu) should be initiated as early as possible for symptomatic outpatients with confirmed, probable, or suspected H5N1, and that close contacts of a person with confirmed H5N1 should receive with oseltamivir.

"Challenges reported in monitoring exposed persons and differences in antiviral recommendations highlight the need to strengthen and standardize public health preparedness and response to [highly pathogenic avian influenza] A (H5N1) viruses in the U.S., particularly if additional animal-to-human A(H5N1) virus transmission events are reported," Kojima and authors wrote.

Of the jurisdictions, 62% reported maintaining stock of antivirals in case of an influenza pandemic.

When epidemiologists were asked if they would recommend an H5N1 vaccine if it were available to veterinary personnel working with H5N1-infected poultry, 67% said they would. However, only 36% said that they would offer such a vaccine to public health personnel monitoring or investigating H5N1-exposed people.

Among the 50 jurisdictions reporting human exposures to H5N1 since January 2022, 88% reported exposures from backyard poultry flocks, 82% from commercial poultry, 54% from wild birds including rescued birds, and 18% from mammals, including farm animals, domestic pets, or wild animals.

The CDC and Council of State and Territorial Epidemiologists conducted the online survey from January 10 to March 6, 2024 -- before the outbreaks of H5N1 in dairy cattle occurred in multiple states and one dairy farm worker in Texas developed conjunctivitis from working with H5N1-infected cattle.

The current outbreak of bird flu has been spreading worldwide since 2020, and the H5N1 clade 2.3.4.4b virus was first identified in wild birds in North America in 2021, the authors noted. In the U.S., wild birds infected with H5N1 were found in 49 states as of February 2022, and in terrestrial and marine mammals in 27 states. Outbreaks in backyard bird flocks or commercial poultry farms have occurred in 48 states.

Correction: This article previously gave percentages of the sources of human exposures to H5N1 since January 2022. This has been changed to reflect percentages of jurisdictions reporting different exposure sources.

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