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A small study in Texas suggests human cases of bird flu may be going unnoticed on dairy farms where the H5N1 virus is spreading rapidly among cows, sparking an unprecedented nationwide outbreak.
The findings confirm what many experts suspected during the outbreak, but the study authors, led by researchers at the University of Texas Medical School at Galveston, go further by explaining candidly why we may not be able to fully monitor, much less contain, a virus with the potential to cause a pandemic.
“Few such studies have been conducted due to concerns that the research might be damaging to the dairy industry,” the authors write. Summary of their researchIt was posted online as a preprint and had not been peer-reviewed.
Study authors led by Gregory Gray were invited to two undisclosed dairy farms in Texas, where outbreaks of H5N1 virus had been occurring in the herds since early and late March, respectively. The researchers had a previously approved research protocol for studying novel respiratory viruses on dairy farms, so they were able to begin their work immediately.
Unusual research
“Farm A” had 7,200 cattle and 180 workers. The disease began on March 6th and it was estimated that about 5 percent of the herd was affected at the time of the outbreak. “Farm B” had 8,200 cattle and 45 workers. After the disease began on March 20th it was estimated that about 14 percent of the herd was affected.
Researchers first visited Farm A on April 3 and Farm B on April 4 to collect swabs and samples at each farm. Based on a previously approved protocol, they were limited to collecting nasal swabs and blood samples from no more than 10 workers per farm. At Farm A, 10 workers provided nasal swabs and blood samples. At Farm B, only seven workers agreed to provide nasal swabs and four provided blood samples.
Swabs taken from cows, milk, dead birds, and fecal slurry samples showed signs of H5N1, but nasal swabs from all 14 people were negative. But when the researchers tested their blood for antibodies that target H5N1 — an indication that they had been previously infected — 2 of the 14 people, or about 14%, tested positive.
The two workers with a history of infection, a man and a woman, both employees of Farm A, reported having flu-like symptoms. The man reported working in close proximity to animals in a cattle enclosure and had been coughing at the time his sample was taken, while the woman reported working in the farm’s cafeteria and had recently recovered from symptoms including fever, cough, and sore throat. She noted that others on the farm had had a similar respiratory illness around the same time as her.
The findings suggest that human infections with H5N1 remain undetected. Moreover, the two undetected infections in a sample of just 14 workers suggests that finding more cases may not be difficult. The Centers for Disease Control and Prevention estimate that about 200,000 people in the United States work in livestock-related jobs.
‘A compelling case’
People who have been infected with the virus At least 175 dairy farms in 13 statesIn the official tally 14 human cases in dairy outbreakFour dairy workers and 10 poultry workers have been infected in connection with the dairy outbreak.
“I’m sure there are more people infected than we know.” “We’re not talking about a single person,” Gray told KFF, which first reported on the study.“That’s mainly because we didn’t monitor it enough.”
All known human infections so far have been mild, but experts worry that each new outbreak presents an opportunity for the insidious H5N1 virus to further adapt to humans — potentially sparking a new pandemic if it evolves to cause more severe disease and spread from person to person.
Federal officials are also concerned about this potential threat. At a press conference on Tuesday, CDC Principal Deputy Director Nirav Shah announced $5 million to vaccinate farmworkers against seasonal flu.
Shah explained that the CDC was concerned that if farmworkers were infected with H5N1 and seasonal influenza at the same time, genetic segments of the viruses could be exchanged, a process known as “swap.” ReunionThat could pose a pandemic threat that experts fear could come as Shah suggested vaccinating workers against the seasonal flu could prevent the virus from mixing in a single person.
The United States has a vaccine specifically for avian influenza. But Shah told the briefing that there are no current plans to use that vaccine on agricultural workers, though the possibility is still under active discussion. Shah said he is against introducing a new vaccine, given that there have been no cases of severe disease from H5N1 infection and no documented human-to-human transmission. “We need strong and compelling evidence,” he added. Shah also suggested that officials expect low vaccination rates among agricultural workers.