Another highly pathogenic avian influenza — or “H5 bird flu” virus — infection in a person in the U.S. has been identified, this time in Michigan. This is the third human case reported in the U.S. since 2022, with the first being associated with poultry exposure, and the most recent two followed exposure to dairy cattle.
Similar to the dairy-related case in Texas, reported on April 1, the U.S. Centers for Disease Control and Prevention individual is a dairy farm worker on a farm where H5N1 virus has been identified in dairy cattle.
While a nasal swab from the individual in Michigan tested negative for influenza, an eye swab sent to the CDC confirmed a positive result for the influenza A(H5) virus, indicating an eye infection. Similar to the Texas case, the patient exhibited only eye symptoms.
Conjunctivitis (eye infection) has been associated with previous human infections with avian influenza A viruses and is part of the current CDC case definition for the virus surveillance. While it’s not known exactly how eye infections result from avian influenza exposures, it may be from contamination of the eye(s), potentially with a splash of contaminated fluid, or touching the eye(s) with something contaminated with A(H5N1) virus, such as a hand.
The CDC has been closely monitoring influenza surveillance systems, especially in the affected states, and there has been no indication of unusual influenza activity in the population, including in syndromic surveillance.
Based on the available information, this infection does not alter the CDC’s current H5N1 bird flu human health risk assessment for the U.S. general public, which remains low. However, individuals with close or prolonged, unprotected exposure to infected birds, other animals (including livestock), or environments contaminated by these animals, are obviously, at a higher risk of infection.
This case was detected through the state’s implementation of recommended monitoring and testing strategies for exposed individuals. Alongside enhanced and targeted surveillance, several measures have been taken to address the situation.
Weekly engagements have been held with state and local health departments to bolster their preparedness. Interim recommendations for worker protection have been updated to include those working with dairy cows and in slaughterhouses. Additionally, a Health Alert Notice was issued on identifying human infections, along with recommendations for investigations and responses. A transition from preparedness to readiness was urged in a call with states.
There have been multiple calls with groups representing farmworkers, and states have been requested to supply personal protective equipment for these workers. Incentives have been announced for workers participating in public health research efforts related to the outbreak. Furthermore, states have been asked to collaborate with clinical labs to increase the submission of positive influenza virus samples to public health labs for subtyping.
»Related: Clinical signs and response to HPAI in dairy cattle herds