What an American farmworker’s bird flu case tells us about tracking the infection

Centers for Disease Control and Prevention

The infection of a dairy worker is important because it confirms that humans can become infected with H5N1 after contact with cows.


An American farm worker who contracted bird flu after working with dairy cattle in Texas appears to be the first known case of mammal-to-human transmission of the virus, a new study shows.

The dairy worker sought medical attention in late March after developing painful, red, swollen and watery eyes with burst blood vessels. However, he had no fever and his lungs were clear, according to a letter about the case published Friday in the New England Journal of Medicine.

He did not report any contact with sick or dead birds or other animals, but did have repeated direct close contact with dairy cows in the same part of the state with other infected herds.

Although the man did not become seriously ill, his case is important because it confirms that humans can become infected with H5N1 after contact with cows. At the same time, it also leaves critical questions unanswered about a virus that the study authors say has “pandemic potential,” and illustrates how difficult it will be to trace infection in this vulnerable population of workers, where positive tests for a disease Infectious disease could mean losing days of work and wages.

“Specifically for farmworkers, these are certainly people who are living in a state of economic desperation, and what they’re not going to do is not get tested for something if they don’t have paid sick leave. , because they can’t afford to be sent home and told to stay home and not work,” said Elizabeth Strater, director of strategic campaigns for the United Farm Workers.

Strater says the UFW, like other groups, has heard rumors that there are dairy workers who are sick but don’t want to get tested, but he said it’s nothing they can confirm.

Health officials in Texas said they tested other sick dairy workers, including some with red eyes, but they turned out to have other illnesses, not bird flu.

“The people tested volunteered to be tested,” said Lara Antón, senior press officer for the Texas Department of State Health Services.

“It is likely that there were other people with symptoms who did not want to be tested, so we cannot say with absolute certainty that no one else contracted H5N1. “We can say with certainty that some of the people on the dairy farms tested positive for other respiratory viruses that commonly circulate among the human population,” Anton said.

In the case of the man who tested positive for bird flu, he took antiviral medications and recovered without lasting problems, and his close family members received the medications as a precaution, the letter said.

courtesy of the New England Journal of Medicine

A farm worker who tested positive for H5N1 bird flu sought care in March for infected, swollen and red eyes.

Swabs of the patient’s eyes and lungs also revealed something interesting: His eyes were full of the H5N1 virus, but there was hardly any virus in his lungs. That could mean that the worker was infected through the eyes (either by rubbing them with contaminated hands or by splashing contaminated milk) rather than through the lungs, and that the virus never migrated there, or that the virus did not migrate. was able to take hold in his lungs. lungs because it was primarily adapted to infect birds, not human airway cells.

The letter about the case was written by researchers from the U.S. Centers for Disease Control and Prevention along with doctors from the Texas Department of State Health Services and researchers from the Texas Tech Bioterrorism Response Laboratory.

Health officials said they could not conduct further investigations into how the man became infected because “epidemiological investigations could not be conducted on the farm” where he worked. They were also unable to test other workers on the same farm.

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That type of testing is critical to answering questions about how the worker became infected, whether others were becoming infected and, if so, how long they were infected and what kind of symptoms, if any, they had.

The CDC is looking for farms that will allow them to conduct such a detailed study.

“Understanding the current avian flu outbreak among dairy cattle is a vital priority to help protect human health,” the agency said in a statement to CNN. “Discussions are underway with farms in multiple jurisdictions to participate in epidemiological studies led by the CDC. Meanwhile, states continue to test symptomatic farmworkers and monitor those who have been exposed to infected animals. CDC also continues to closely monitor a robust nationwide flu surveillance system. To date, it has not detected any unusual flu activity.”

At a news conference Friday, White House spokeswoman Karine Jean-Pierre said the administration was following the situation “very closely and taking it very seriously.”