The Centers for Disease Control and Prevention (CDC) has reported a second human case of bird flu linked to the ongoing outbreak among dairy cows in the United States. The outbreak involves a strain of avian influenza known as H5N1, which has been detected in cattle in nine states. Health officials emphasize that the commercial milk and meat supply is safe for consumption, but raw milk samples from infected cows have been found to carry the virus.
Although no human infections with H5N1 have been linked to consuming raw milk, both human cases reported so far have affected dairy workers employed by farms with H5N1-infected cows. The first case, reported in April in Texas, involved an individual whose only symptom was eye redness. The second case, recently identified in Michigan, also presented with eye-related symptoms.
The person infected in Michigan tested negative for bird flu when a swab sample was taken from their nose, but an eye swab from the patient tested positive. The CDC is currently analyzing the genetic makeup of the virus that infected the Michigan patient and expects to release those data soon.
According to the CDC, it is not yet fully understood how eye infections can result from avian influenza exposure. It is possible that they may arise from contamination of the eyes with a splash of contaminated fluid, such as milk, or through contact with a hand carrying the virus.
While the CDC considers the risk of bird flu spread to the general public to be low, it acknowledges that additional human cases could be identified given the high levels of the virus in raw milk from infected cows and the extent of its spread among dairy cattle. However, sporadic human infections without ongoing spread will not alter the CDC’s risk assessment for the general population in the United States.
The CDC has issued guidelines for individuals who work with H5N1-infected animals or those potentially exposed to the virus. These recommendations include avoiding close, long, or unprotected exposures to sick or dead animals, including wild birds, poultry, and cows. Additionally, people should avoid unprotected exposure to the animals’ poop, bedding, unpasteurized milk, and materials that have been in close contact with animals with suspected or confirmed H5N1 infections.
H5N1 is known to be deadly to poultry, but in humans, the symptoms triggered by the virus can vary widely, from being completely absent to severe respiratory illness. Only three cases of human H5N1 infection have ever been reported in the U.S., and all have been mild. Available drugs for the seasonal flu can treat the infection in people.
Initial genetic testing of the virus on farms has not indicated any mutations that would make it more likely to spread easily between people. However, the CDC is closely monitoring the situation with that possibility in mind.
