Colorado bird flu cases suggest extreme heat may be complicating efforts to control the virus

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

“At the time when transmission is believed to have occurred, temperatures in Colorado were over 104 degrees Fahrenheit,” said Dr. Nirav Shah, principal deputy director of the Centers for Disease Control and Prevention, which is investigating the outbreak along with the Colorado Department of Public Health and Environment.

This has made it difficult to use personal protective equipment, Shah said.

Additionally, to cool the sweltering barns, large industrial fans were used to blow air through them, moving dust and feathers along with it – feathers from infected birds are known to carry the H5N1 virus.

“We understand that the large fans were moving large volumes of air, making it difficult for workers to maintain a good seal and fit with their masks and eye protection,” Shah said.

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

This incident rapidly doubled the number of farmworkers known to be infected with the H5N1 virus in the United States, making it the largest number of workers ever known to be infected and associated with a single farm.

In 2022, a poultry worker in Colorado tested positive for H5N1. Four other farm workers have tested positive for H5N1 this year. The test came back positive. One person in Texas, two in Michigan and one in Colorado have been confirmed to have the virus after working with infected dairy cows, and the number of cases is thought to be undercounted because farmworkers are often reluctant to get tested for fear of losing their jobs and income.

Shah said genetic analysis of the virus from one of the recent human cases linked to poultry culls was reassuring because it showed no mutations that would suggest the virus could easily infect humans. Tests also found that the virus is closely related to a strain infecting cattle.

At Colorado’s request, the CDC has deployed a 10-person team to help investigate the outbreak and conduct contact tracing. Shah said 60 people have shown symptoms consistent with avian flu, and all but five have tested negative at a state lab.

“We’ve seen an aggressive rollout of testing at this farm in Colorado,” he added.

None of the workers were hospitalized, and most had common flu symptoms — conjunctivitis, eye infections, fever, chills, cough and sore throat. They were given antiviral medication and are recovering.

About 160 people are helping to cull 1.8 million laying hens at a Colorado farm that officials are not naming as a “large-scale” egg production operation, and is expected to continue for the next 10 to 14 days.

Dr. Eric Deeble, deputy senior adviser for H5N1 response at the USDA, said it is unclear how the birds became infected, but the virus isolated from them is closely related to the same strain that is infecting dairy cows.

The CDC maintains that the threat posed by the H5N1 avian influenza virus to the general public is low.

But recently the disease has spread from domestic animals and wild birds to dairy cows and other mammals, putting farm workers at high risk of infection.

To stay safe, The CDC recommends Workers handling sick or dead cattle or birds must wear personal protective equipment (PPE) such as waterproof coveralls, face masks, goggles or face shields, boots, gloves and head covers.

Although workers involved in culling chickens in Colorado were required to wear uniforms, the environmental conditions made it difficult for them to continue wearing them. “We recognize that the use of PPE, particularly masks and eye protection, was suboptimal,” 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 US this summer, and has called on the CDC to rethink its PPE guidelines so more people can follow them.

“There’s no reasonable way to protect themselves from either the virus or heatstroke, and yet these people are being asked to risk their lives for a virus that we don’t even understand,” Elizabeth Strater, strategic campaigns director for the United Farm Workers union, said Tuesday. “They’re being put in an impossible position.”

Workers wear liquid-tight coveralls, Strater noted, which can block sweat cooling and make workers heat up more quickly, and in dirty, damp environments like barns, masks and respirators can become clogged or wet within minutes.

The CDC said it is working to refine its PPE recommendations to take heat into account: “We have brought in industrial hygienists as part of our team who are experts on this issue and can help implement improved engineering controls that will make PPE use more uniform and more acceptable,” Shah said.

Strater said it’s time for the CDC to consider vaccinating farmworkers, as Finland has done, to further protect them and the general public from the virus and the threat of a new pandemic if it spreads.

“We need to prioritize them not just because it’s moral to prioritize them for vaccination and protect their lives, but because they’re a relatively small number of people, given the kind of firewall that they’re building around the general public,” she said. “We don’t have a large number of people that we have to protect. These are people that are on the front lines, at very close risk.”

U.S. health officials have stressed that they have no plans to distribute an H5N1 vaccine, but they are preparing to deploy several candidate vaccines in case the virus becomes more dangerous.

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

Early July, HHS Announcement The agency announced it has paid Moderna Inc. $176 million to help develop an mRNA-based vaccine against H5N1. The agency said it expects results from a Phase 1 clinical trial on the vaccine’s safety by the end of the year.