Arizona confirms first human cases of H5 bird flu

Arizona has confirmed its first two human cases of H5 bird flu in poultry workers, according to the state’s health department. Both individuals have recovered after experiencing mild symptoms.

In a statement released on Friday, the Arizona Department of Health Services (ADHS) announced the cases of avian influenza H5. “Both individuals were exposed to infected poultry while working at a commercial facility in Pinal County,” the statement said. “These individuals reported mild symptoms, received treatment, and recovered.”

Pinal County, located between Phoenix and Tucson, is part of the Phoenix metropolitan area. On November 15, county officials confirmed the presence of avian influenza in poultry at a commercial farm after birds exhibited clinical signs consistent with the disease. However, it remains unclear whether the infected workers were linked to this specific farm.

While the ADHS confirmed the H5 avian flu infections, further analysis is required to determine the exact subtype, but H5N1 is the most likely. A newer strain of H5N1, clade 2.3.4.4b, has raised global concern due to its widespread presence and mutations that may facilitate easier transmission in mammals.

Arizona’s first confirmed cases are part of a broader pattern of H5N1 infections among poultry and dairy workers in the United States. So far this year, there have been over 60 cases reported across eight states, with the majority occurring in California.

LINK: A list of all human cases of H5N1 bird flu since 2021

Most U.S. cases have been linked to poultry or dairy exposure. However, two cases—one in California and one in Missouri—have no known connection to poultry or dairy, sparking concerns that the virus might be spreading through other mammals or alternate transmission methods.

A similar situation was reported in Canada’s first human H5N1 case, detected in early November. The patient, a teenager with no ties to poultry or dairy, is being treated in a hospital in British Columbia and was last reported to be in critical condition. Experts maintain there is currently no evidence of human-to-human transmission.

Globally, 79 human cases of H5N1 bird flu have been reported this year, including 64 in the United States, 10 in Cambodia, two in Vietnam, and one each in Australia, Canada, and China. The newer clade 2.3.4.4b variant has been identified in the Canadian case and all U.S. cases, which include 33 in California, 14 in Washington, 10 in Colorado, two in Arizona, two in Michigan, and one each in Texas, Oregon, and Missouri.