H5N1 bird flu: Second person infected in US with main symptom of conjunctivitis

(Image credit: AdobeStock/Tunatura)

There is a current outbreak of H5N1 globally in poultry and other animals. H5N1 is a very contagious strain of avian influenza A that, thus far, has been confirmed in 9 states in dairy cows and in 2 individuals. The government of Australia reported infection in a child with a different strain than the current one in the US on Tuesday, May 21.

According to the CDC, there has been no human-to-human spread associated with the 2 cases.

The first case was reported in Texas in a dairy worker in March 2024. A second affected person, reported on Wednesday, May 22, is a farmworker at a Michigan dairy farm. The pediatric case in Australia followed a trip to India.

Alert to ophthalmologists and optometrists

The only symptom in the Michigan farmworker was conjunctivitis; the patient tested positive for the bird flu based on an eye swab; a nasal swab was negative. According to the CDC, the first case was notable in that it was the first time this strain of H5N1 had been detected in cows and the first instance of cow-to-human transmission.

In a press release, the CDC said, "Based on the information available, this infection does not change the current CDC’s H5N1 bird flu human health risk assessment for the U.S. general public, which the agency considers to be low.”

Bird flu symptoms

The symptoms can vary widely in the degree of severity, that is, from no symptoms or mild flu symptoms to severe cases requiring hospitalization for pneumonia and respiratory failure, the CDC reported.

According to the CDC, the reported signs and symptoms of bird flu are as follows: fever, cough, runny nose, muscle aches, headache, fatigue, shortness of breath, conjunctivitis, diarrhea, nausea, and vomiting.

An infection with bird flu viruses cannot be diagnosed by signs or symptoms alone, the CDC says. Laboratory testing is required.

Flu transmission

The World Health Organization (WHO) has reported that human-to-human transmission is rare.

The Avian flu spreads from infected birds to humans by direct contact with an infected bird, from environments contaminated with bird flu viruses, or through a host, such as another animal.

Interestingly, the CDC reported that it is unknown how conjunctivitis results from avian influenza exposures and theorized that “a splash of contaminated fluid, or touching the eye(s) with something contaminated with the Avian (H5N1) virus, such as a hand. High levels of the Avian (H5N1) virus have been found in unpasteurized milk from H5N1-infected cows," according to the CDC.

However, the WHO referred to the potential risk of the bird flu spreading to humans as “an enormous concern,” and warned about the potential for the virus to acquire the ability to spread more efficiently between people.

It appears that the bird flu is not transmitted to humans from chicken, eggs, or beef products that are well-cooked or from pasteurized milk.

The CDC specifically recommends avoiding direct contact with wild birds and visiting poultry farms. If a person is in contact with poultry, they should wear a mask and eye protection and wash hands immediately afterward. It also is advised that if an individual is ill after contact with birds, they should visit a doctor.