3rd Human Case of Bird Flu In US: What Are The Symptoms? – TODAY

A third person in the United States has tested positive for avian influenza, aka bird flu, amid an ongoing outbreak affecting poultry and dairy cattle.

The case was detected in a farmworker in Michigan who was exposed to sick cows, the U.S. Centers for Disease Control and Prevention said on Thursday.

Since March, a highly contagious strain of avian influenza A (H5N1) has spread to over 60 dairy cattle herds in nine U.S. states. In addition to the three human cases in the U.S., a child in Australia was also recently infected with bird flu.

Bird flu is a disease caused by infection with avian influenza A viruses, which occur naturally among wild aquatic birds and circulate among poultry, TODAY.com previously reported.

Occasionally, bird flu viruses spread to mammals, and rarely, to humans. The highly pathogenic H5N1 strain causing the U.S. outbreak is severe and often fatal in birds, but appears to be mild in cows.

No known human-to-human spread has occurred with the current H5N1 strains, per theU.S. Centers for Disease Control and Prevention. The risk to the general public is low, but the outbreak has sounded the alarm among health officials in the U.S. and abroad, who are monitoring bird flu viruses closely.

The latest case marks the second farmworker in Michigan to test positive in one week and the third human case detected in the U.S. in the last two months. None of the three cases are connected and all occurred at different farms, the CDC said.

The first human case associated with the multi-state H5N1 outbreak among cows was reported in a dairy worker in Texas in March. It was the first time this strain of H5N1 referredto ashighly pathogenicavian influenza A (HPAI) had been detected in cows and the first instance of cow-to-human transmission, according to the CDC.

The current bird flu strain that were concerned with, H5N1, has been circulating around the world for quite some time, Dr. William Schaffner, professor of infectious diseases at Vanderbilt University Medical Center, previously told TODAY.com.

The Texas dairy worker and the first farmworker in Michigan to test positive both reported pink eye as their only symptoms. The third patient also had eye symptoms, as well as a cough and fever, officials said. The second patient in Michigan is the first to report upper respiratory symptoms associated with the bird flu infection.

"Based on the information available at this time, this case does not change CDCs current A(H5N1) bird flu human health risk assessment for the U.S. general public. The risk to members of the general public who do not have exposure to infected animals remains low," the CDC said.

Bird flu infections in humans can range in severity, experts note. Some people have no symptoms at all or only a mild flu-like illness, while others develop severe disease requiring hospitalization, according tothe CDC.

It can be a serious infection with a high mortality rate, said Schaffner.

According to the CDC, reported signs and symptoms of bird flu include:

Bird flu in humans may look similar to seasonal influenza flu or upper respiratory infection. In severe cases, bird flu can lead to pneumonia, respiratory failure and other complications, TODAY.com previously reported.

The recent case of H5N1 in the child in Australia was a severe infection, but the child fully recovered. Victorian health officials did not release additional details about the patient's symptoms.

The dairy worker in Texas who tested positive for H5N1 in March had a mild infection, with eye redness or conjunctivitis (pink eye) as the only symptom,the CDC said. The patient was treated with flu antivirals and recovered.

Similarly, the first farmworker in Michigan who tested positive for H5N1 only reported eye symptoms, per the CDC.

The third farmworker who tested positive reported eye symptoms, including discomfort and watery discharge, a cough, and a fever. They are being treated with antivirals and recovering, the CDC said.

The only other human case of H5N1 in the U.S., which was reported in Colorado in 2022, was a mild infection as well.

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

Transmission of bird flu viruses to humans is very rare. According to the WHO, since 2003, there have been 889 cases and 463 deaths caused by H5N1 in 23 countries.

Avian influenza can spread from infected birds to humans in a few ways, per the CDC:

Infected birds can shed the virus in their saliva, nasal secretions, mucus and feces, TODAY.com previously reported. People can become infected when the virus particles get into the mouth, nose, eyes or are inhaled, says Schaffner.

Humans typically become infected with bird flu viruses through close, unprotected contact with an infected bird.

When it comes to the dairy workers with conjunctivitis, the CDC noted it's press release that "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. High levels of A(H5N1) virus have been found in unpasteurized milk from H5N1-infected cows."

Human-to-human transmission of bird flu viruses is extremely rare. The few cases that have been documented have occurred primarily through prolonged, unprotected contact between a symptomatic person and a family member or caregiver, per the CDC.

"The virus doesnt have the (genetic) capacity to spread easily from person to person, says Schaffner.

However, in arecent press conference, the chief scientist of the World Health Organization called the risk of the bird flu spreading to humans an enormous concern, and warned about the potential for the virus to acquire the ability to spread more efficiently between people. Scientists are closely monitoring bird flu viruses for any changes.

There is no evidence that humans can get bird flu from chicken, eggs, or beef that's been properly prepared and cooked, and it is safe to drink pasteurized milk, experts say.

The risk of getting bird flu is low, but the CDC recommends people:

Caroline Kee is a health reporter at TODAY based in New York City.

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3rd Human Case of Bird Flu In US: What Are The Symptoms? - TODAY