Study suggests bird flu infections may be going undetected among farm workers : Shots

New research supports fears that more livestock workers may be infected with avian flu than reported.

“We're confident that more people are infected than we know about,” said Gregory Gray, an infectious disease researcher at the University of Texas Medical Branch, who led the study. Posted online Wednesday “The main reason is that we didn't do enough surveillance,” he said.

Under-reporting of bird flu cases could delay health officials' awareness if the virus becomes more contagious: A surge in infections outside farmworker communities would trigger government flu surveillance systems, but by then it may be too late to contain it.

“We need to think about what we can do to stop this,” Gray said. “It's not just going to go away.”

The Centers for Disease Control and Prevention makes decisions based on surveillance — for example, they have the avian flu vaccine but decided not to offer it to farm workers because of the low number of cases.

But testing of farmworkers for avian flu remains rare, which is why Gray's study stands out as the first to look for signs of previous, undiagnosed infection in people who came into contact with sick dairy cows and then fell ill and recovered.

Gray's team found signs of previous avian flu infection in workers at two dairy farms affected by outbreaks in Texas earlier this year. They analyzed blood samples from 14 farmworkers who hadn't been tested for the virus and found antibodies in two of them — a hit rate of nearly 15 percent for just two of the more than 170 dairy farms affected by avian flu outbreaks in 13 states this year.

One of the workers with antibodies had been taking medicine for a persistent cough when she consented to researchers analyzing her blood in April, while the other had recently recovered from a respiratory illness, which she told researchers she didn't know the cause but that other farmworkers around her who hadn't been tested had also gotten sick.

Richard Webby, director of the World Health Organization Collaborating Center for Influenza at St. Jude Children's Research Hospital in Memphis, Tennessee, said the results confirmed his suspicions that the 13 human cases of avian flu reported by the CDC this year were an undercount.

“What we're seeing may not be the tip of the iceberg, but it's certainly not the whole story,” Webby said.

Very little testing of farm workers

Though small, the study lends new urgency. Reporting undiagnosed illness Infections are spreading among farmworkers and veterinarians, and the CDC warns that simultaneous infection with seasonal and avian flu could cause the two viruses to swap genes, allowing avian flu to spread from person to person just as easily as seasonal flu.

There is currently no evidence that this is happening, and asymptomatic cases of bird flu appear to be rare, he said. Michigan antibody study The CDC announced the findings on July 19. Researchers analyzed blood samples from 35 workers at an affected dairy farm in Michigan and found no signs of missed infections. Unlike in the Texas study, these workers did not get sick.

“It's a small study, but it's a first step,” said Michigan's chief medical officer, Dr. Natasha Bagdasarian. The state is stepping up testing of farmworkers, but the effort is complicated by systemic issues, including precarious employment, which can make them at risk of being fired for calling in sick, she said.

Gray said without more support for farm workers and cooperation between the government and the livestock industry, the U.S. risks remaining in the dark about the virus.

“There's a lot of genomic research and lab research, but the real work is happening on the farm, and we're not monitoring that,” Gray said.

Breakdown of communication

A Colorado dairy worker told KFF Health News that he went to see a doctor about a month ago for eye irritation, a common symptom of bird flu. The doctor ran the usual tests and also did a urine test. But the farm worker had never heard of bird flu, and the doctor didn't mention it or test for the virus. “They told me there was nothing,” the worker said in Spanish, speaking on the condition of anonymity for fear of retaliation from his employer.

The dairy worker and two other workers in Texas said their employers aren't providing them with the goggles, N95 masks and aprons to protect them from milk and other fluids that may be contaminated with the virus, and tight finances make it hard for them to buy their own gear.

Same goes for going to the doctor. One Texas worker said he suffered from a piercing headache and sore throat but went untreated because he didn't have health insurance and couldn't afford the costs. He attributed these symptoms to working long hours in a stuffy barn with limited water. “They don't give you water or anything,” he said. “You bring your own bottles.” But without testing, there's no way to know if the symptoms are due to bird flu or something else.

About one-fifth of farm workers are uninsured. According to KFF's analysis:a similar percentage of households have annual household incomes below $40,000.

The three farmworkers had never heard about avian flu from their employers or state health officials and were not offered testing. The CDC said Recent Updates Facebook said its partnership with Meta, the company that owns Instagram, resulted in posts about bird flu appearing on computer and smartphone screens more than 10 million times.

That support doesn't reach farmworkers who don't scroll, don't speak English or Spanish or don't have smartphones or internet, said Bethany Boggess Al-Khauter, research and public health program director at the National Farmworker Health Center. She and others said protective equipment from health officials isn't reaching farms.

“We're hearing that employers are hesitant to take them up on the offer,” said Christine Sauve, policy and engagement manager at the Michigan Immigrant Rights Center. “If this starts to spread easily from person to person, we're in trouble, because farmworker housing units are very crowded and have poor ventilation.”

If a sick farmworker seeks medical care, the clinic may notify health authorities, but many farmworkers do not seek medical care because they do not have health insurance and risk being fired if they miss work.

“The biggest fear we hear is that they will face retaliation from their employer or be blacklisted from other jobs,” Sauve said.

Influenza Surveillance

The CDC assesses the current avian influenza situation as a low public health risk because the national influenza surveillance system has not generated any alarms of concern.

The system scans for unusual increases in visits to hospitals, where it finds that nothing unusual has happened, and also analyzes some of the patient samples for unusual strains of the flu virus. Since late February, officials have tested about 36,000 samples, but none have detected bird flu.

But Samuel Scarpino, an epidemiologist who specializes in disease surveillance, says the system will miss many emerging health threats because, by definition, it starts with a relatively small number of infected people. According to the CDC, roughly 200,000 people in the United States work on farms that raise livestock. That's just 0.1% of the U.S. population.

Scarpino said that if people start dying from bird flu — all 13 confirmed cases so far have been mild — the CDC's surveillance system would be triggered, and if the virus spreads beyond farmworkers and their close contacts, the surveillance system would detect a surge in infections, but by that point it may be too late to contain it.

“We don't want to get into a COVID-19 situation again,” Scarpino said, recalling when schools, restaurants and businesses were forced to close because the coronavirus spread too widely to be controlled through testing and targeted isolation of individuals. “By the time we started to understand the number of cases, there were so many, we were left with bad options,” he said.

Worrying Signs

Researchers warn that the H5N1 avian influenza virus has evolved over the years to become more infectious in mammals, including humans, underscoring the need to keep a close eye on what's happening as the outbreak spreads to dairy farms across the country.

Bird flu viruses appear to spread primarily through milk and milking equipment. But for the first time, researchers have found that In MayAnd July It did not spread efficiently through the air between laboratory ferrets a few inches apart, and Cow experimentSome cows became infected by inhaling tiny droplets containing the virus, the kind that can happen if an infected cow coughs near other cows.

Cows do cough, and a new study from Texas notes that cows coughed and showed other signs of respiratory disease during outbreaks on farms.

There were other ominous observations: At one farm, at the peak of the infection, about half of the approximately 40 cats suddenly died, likely from drinking raw milk contaminated with the avian flu virus.

Most people diagnosed with bird flu contract it from animals. In the new study, Gray found signs that the virus can also spread from person to person, but added that this is still only speculation. One of the two people who had antibodies worked in the farm's cafeteria next to the dairy, alongside farm workers but not with cows.

“We need to find better ways to monitor so we can make informed decisions, not decisions based on guesswork,” he said.

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