Public concern over bird flu ratcheted up this week as the H5N1 virus continued its sweep through the nation’s dairy and poultry farms and the first American was hospitalized with a severe infection.
Federal officials reported Wednesday that an older person in Louisiana was “severely” ill after being infected by poultry from a backyard flock. The person, who was not identified by name, is one of 61 people identified infected in the U.S. so far this year.
In other countries, bird flu has killed about half of those known to be infected, but here in the United States there have been no deaths and only mild illnesses until this week.
The Louisiana patient was the first American confirmed to be sickened by a backyard flock. The strain of H5N1 bird flu that infected that patient is different from the one that has infected cattle, poultry and farmworkers for most of this year, CDC said, though it is similar to one found in wild birds and in a person infected in Washington State and a teen in British Columbia.
Here’s what you need to know as the CDC and other federal and state agencies work to contain the virus:
People in close contact with infected animals, such as dairy or poultry workers, are at increased risk of infection with bird flu.
People with backyard flocks or who hunt fowl should take precautions handling birds, CDC said.
Pasteurized milk and milk products are safe, repeated testing has shown. Public health officials warn against drinking raw milk, which in some cases has been found to contain enough virus to cause disease, though no one has yet been known to be infected via milk.
Most people infected with bird flu in the U.S. have had mild symptoms.
Symptoms of H5N1 birth flu infection in humans may include pink eye, fever, fatigue, cough, muscle aches, sore throat, nausea and vomiting, diarrhea, stuffy or runny nose and shortness of breath, according to the Cleveland Clinic.
While data is limited, experts from the College of American Pathologists said the farmworkers might have had different symptoms than others infected either because of different strains of the virus, or because they were infected in different ways.
The farmworkers, for instance, may have rubbed their eyes after touching a cow that was contaminated with the virus, and then developed red eyes ‒ the most common of their symptoms. By contrast, someone who came into contact with a backyard chicken or wild bird, might have inhaled the virus and therefore become sicker.
The patient in Louisiana, who was exposed by a backyard flock, is experiencing severe respiratory symptoms and is in critical condition, according to Emma Herrock, communications director for the Louisiana Department of Health.
The patient is also reported to have underlying medical conditions and is over the age of 65, putting them at extra risk for complications from the flu, Herrock said via email.
Health officials have yet to call for the use of vaccines against bird flu given that there is no evidence of spread between people, relatively few people have been infected and most infections have been mild.
During winter respiratory virus season, officials have worked to get the country’s 200,000 livestock workers vaccinated against the seasonal flu. While regular flu vaccines don’t provide protection against H5N1, officials are concerned that if someone caught both versions of the flu at once, the virus strains could combine, leading to a more severe or infectious form of bird flu.
At the same time, federal officials have prepared about 10 million doses of H5N8 vaccine that they think will be effective against H5N1 bird flu, in case the virus becomes more dangerous.
Worried about an outbreak in its mink industry that might spread to workers, Finland distributed similar vaccines to its livestock workers this summer.
The U.S. has also poured funding to research vaccine candidates against bird flu. A study of Moderna’s mRNA vaccine published Wednesday showed promise, producing immune responses against the virus in ferrets, an animal commonly used to test flu vaccines. Researchers at the University of Pennsylvania have developed a different experimental mRNA vaccine, which prevented severe illness and death among infected ferrets.
Scientists have also been trying to develop vaccines to protect animals, especially valuable dairy cows. As of Thursday, the virus had infected 875 herds across 16 states, according to U.S. Department of Agriculture data.
USDA has approved seven vaccine field safety trials in cattle, Dr. Eric Deeble, a high-ranking agency official, told reporters on Wednesday, though it’s still early in the vaccine development process.
When SARS-CoV-2 was first identified, there were no tests for it. By contrast, there is already a test that can readily identify H5N1, said Dr. Ben Bradley, assistant professor at the University of Utah School of Medicine’s pathology department.
“What we’re facing with H5N1 is a very different landscape than COVID-19,” Bradley said in a College of American Pathologists (CAP) briefing on Friday.
However, Bradley said he’s paying attention to any red flags that could indicate the potential for a bigger outbreak.
The first would be any cases likely transmitted from person to person.
Bradley is also concerned that some people may have been infected without knowing it. Tests have shown some dairy workers had antibodies for H5N1, which could suggest the virus may be spreading faster − and more discreetly − than previously thought.
Although the CDC reported 61 confirmed cases of bird flu in the U.S., multiple experts told USA TODAY the real figure is likely higher.
“Not quite knowing the full picture of things right now is concerning,” said Bradley, also medical director of virology at ARUP, a national testing laboratory.
If the virus continues to infect more people and animals, it will have more opportunities to mutate, potentially becoming more contagious or dangerous.
“We’re in a situation where we need to be alert to the possible threat of this,” Bradley said.
It’s impossible to guess whether bird flu will eventually become a more significant threat, said Dr. Donald Karcher, CAP president and professor at George Washington University Medical Center.
“This is a random process that viruses undergo and it’s really hard to predict when that event is going to happen,” he said.
Adrianna Rodriguez can be reached at adrodriguez@usatoday.com.
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