A US farmworker who caught 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 care in late March after developing painful red, swollen, weeping eyes with burst blood vessels. He had no fever, however, and his lungs were clear, according to a new letter about the case published in the New England Journal of Medicine on Friday.
He reported no contact with sick or dead birds or other animals, but he did have repeated, direct, close contact with dairy cows in the same part of the state with other infected herds.
Digitally-colorized transmission electron microscopic image of Avian Influenza A H5N1 virus particles (seen in gold), grown in Madin-Darby Canine Kidney (MDCK) epithelial cells (seen in green). Cynthia Goldsmith/CDC
Even though the man didn’t become seriously ill, his case is important because it confirms that humans can be infected with H5N1 after contact with cows. At the same time, it also leaves critical questions unanswered and illustrates how hard it will be to track the infection in this vulnerable population of workers, where testing positive for an infectious disease might mean losing days of work and pay.
“For farmworkers specifically, certainly these are folks that are that are living in a state of economic desperation, and what they’re not going to do, is they’re not going to test for something if they don’t have paid sick leave, because they cannot afford to be sent home and told to stay home and not work,” said Elizabeth Strater, who is director of strategic campaigns for United Farm Workers.
Strater says UFW, like other groups, has heard rumors that there are dairy workers who are sick, but don’t want to be tested, but she said it’s nothing that they’re able to confirm.
Health officials in Texas said that they did test 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 Anton, senior press officer with the Texas Department of State Health Services.
“It’s likely 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 for sure some of the people on dairy farms tested positive for other respiratory viruses that are commonly circulating in the human population,” Anton said.
In the case of the man who did test positive for bird flu, he and his and his close family members were given antiviral medications and they recovered without any lasting problems, the letter says.