Cases of bird flu in Colorado suggest extreme heat may complicate efforts to control virus

CNN
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The scorching heat may have played a role in the infections of five workers who fell ill last week while culling a large flock of chickens infected with the H5N1 virus in Colorado, health officials said Tuesday.

“At the time the transmission would have occurred, it was 104 degrees or higher in Colorado,” and it was probably hotter in the barns, said Dr. Nirav Shah, deputy director of the U.S. Centers for Disease Control and Prevention. The CDC is investigating the outbreak with the Colorado Department of Public Health and Environment.

That made using personal protective equipment a challenge, Shah said.

In addition, large industrial fans were blown to bring down temperatures in the sultry barns, moving air, dust and feathers. Feathers from infected birds are known to carry the H5N1 virus.

“We understand that those large fans were moving so much air that workers were having a hard time maintaining a good seal or a good fit, either between the mask or with eye protection,” Shah said.

Four of the Colorado cases have been confirmed by the CDC. A fifth tested positive at a state lab and has been sent to the CDC for confirmation.

The incident quickly doubled the number of farmworkers known to be infected with the H5N1 virus in the United States, making it the highest number of workers known to be infected on a single farm.

In 2022, a poultry worker tested positive for H5N1 in Colorado. This year, four other farm workers have tested positive — one in Texas, two in Michigan and another in Colorado — after working with infected dairy cattle. The number of cases is thought to be undercounted because farm workers are often reluctant to get tested for fear of losing jobs and income.

Genetic analysis of the virus from one of the recent human cases involved in the poultry cull was reassuring, Shah said, because it showed no mutations that would indicate the virus spreads more easily to people. Testing also showed the virus was closely related to the strain spreading among cattle.

At the request of the state of Colorado, the CDC has sent a 10-person team to assist with investigation and contact tracing in the outbreak. Sixty people have shown symptoms consistent with bird flu, and all but five have tested negative at a state lab, Shah said.

“We have seen a significant increase in testing on this particular farm in Colorado,” he added.

None of the workers were hospitalized and many had traditional flu symptoms including conjunctivitis or eye infections, fever, chills, cough and sore throat. The workers have been given antiviral medication and are recovering.

In all, about 160 people are involved in the culling, or killing, of 1.8 million laying hens at the Colorado farm, a “major” egg production operation that officials did not name. The culling operation is expected to last another 10 to 14 days.

It’s not clear how the birds became infected, but the viruses isolated from the birds are closely related to the same strain that infects dairy cattle, said Dr. Eric Deeble, the U.S. Department of Agriculture’s acting senior adviser for the H5N1 response.

According to the CDC, the threat to the public from the H5N1 bird flu virus is low.

However, farm workers are at greater risk of contracting the infection. The disease has recently spread from domestic and wild birds to dairy cattle and other mammals.

To stay safe, the CDC recommends that people who work with sick or dead livestock or birds wear personal protective equipment (PPE). This equipment includes waterproof coveralls, a face mask, safety glasses or a face shield, boots, gloves, and a head covering.

Workers involved in the culling of the Colorado chickens were required to wear full uniforms, but environmental conditions made it difficult to maintain that. “We understand that the use of PPE was not optimal, particularly the masks and eye protection,” Shah said.

The United Farm Workers union has questioned whether the CDC’s recommendations are practical, given the record heat that has hit much of the United States this summer. The union called on the CDC to reconsider its PPE guidelines so more people could follow them.

“These are people who are being asked to put their lives on the line for a virus that we don’t understand very well, and they have no reasonable way to protect themselves from the virus or from heat illness,” Elizabeth Strater, director of strategic campaigns for United Farm Workers, said Tuesday. “They’re being put in an impossible position.”

Workers wear liquid-tight coveralls, Strater points out, which prevent sweat from cooling their bodies, making them prone to overheating. In dirty, wet environments like a barn, masks and respirators can become clogged or soaked in minutes.

The CDC said it is working to refine its PPE recommendations to take the heat into account. “We have sent as part of our team a specialist in these matters, an industrial hygienist who can help implement enhanced engineering controls that can make the use of PPE more uniform and palatable,” Shah said.

Strater said it’s time for the CDC to consider vaccinating farmworkers, as Finland is doing, to give them — and the general public — an extra layer of protection against the virus and against the threat of a new pandemic if the virus spreads.

“They should be prioritized, not only because it’s morally right to protect their lives by prioritizing vaccination, but it’s a relatively small group of people when you think about the kind of firewall they’re creating around the rest of the general public,” she said. “This is not a huge number of people that we need to protect. These are people who are on the front lines and who are so intimately exposed.”

While US health officials have stressed that they have no plans to distribute an H5N1 vaccine, they are preparing several vaccines that could be deployed if the virus becomes more dangerous.

In May, the U.S. Department of Health and Human Services announced that it was ordering 4.8 million doses of H5N1 vaccine, which would be produced from bulk ingredients in the nation’s Strategic National Stockpile. Those doses are expected to be ready by the end of this month.

In early July, HHS announced that it had paid Moderna $176 million to support the development of an mRNA-based vaccine against H5N1. The agency said it expects to see results from a phase 1 clinical trial on the safety of that vaccine by the end of the year.