Is heat wave helping spread of bird flu?

The largest U.S. human bird flu outbreak may be due in large part to the extreme heat now covering much of the country.

Four cases of avian influenza among poultry processors in Colorado have been confirmed by the Centers for Disease Control and Prevention and a fifth case is expected to be positive, though its lab result is pending. Officials said that the Colorado heat wave has likely made personal protective equipment less effective among the workers.

The Guardian noted it’s the first cluster of human cases of H5N1 bird flu reported in the U.S. The article said the “workers were culling a flock of egg-laying chickens that had tested positive for H5N1.” Officials reported it was 104 degrees Fahrenheit outside and even hotter in the chicken houses.”

In a media briefing Tuesday, the CDC’s primary deputy director, Nirav Shah, told reporters that the workers’ sweat and the gigantic industrial fans made it very hard to keep the goggles and masks the workers wear sealed. And the fans were likely blowing feathers and other virus-contaminated material, aiding in the spread.

The workers were expected to wear Tyvek suits, respirators, goggles, boots and gloves in the extreme heat as they culled the flock of 1.8 million chickens in an infected flock.

Poultry worker outbreak has worse symptoms

Officials said that of the 160 farm workers, 60 had some symptoms, but only the four or five have proven to have bird flu, based on results from Colorado’s state health lab. The CDC lab does further testing to confirm the results. The public health experts noted that only the workers who had symptoms were tested. Shah said more cases may be found as the investigation goes on.

Because the flock includes 1.8 million birds, the culling is an ongoing process that will last at least a couple more weeks. “USDA considers it very important for depopulation to continue to stop virus amplification and shedding, prevent further spread and to reduce the viral load in the environment,” Eric Deeble, U.S. Department of Agriculture senior advisor for H5N1 response, said during the media briefing.

Shah said the CDC sent 10 experts, among them an environmental hygienist, to help reduce worker exposure to avian flu as they handle the infected chickens.

Outbreaks in cows, chickens related

The Guardian article reported that “genomic sequencing shows that these cases are closely related to the outbreak in dairy cows; it seems to have jumped from cows to chickens to people, though it’s not clear how at this point. A USDA report from Michigan last month found the virus may be transported by people between farms.”

According to CNN , “Genetic analysis of the virus from one of the recent human cases involved in the poultry culling was reassuring, Shah said, because it didn’t show any mutations that might indicate the virus is spreading more readily to people. Testing also showed that the virus was closely related to the strain spreading in cattle.”

Unlike several cases in humans related to this outbreak in dairy cows, where workers’ only symptom was pink eye, the Colorado poultry workers also reported that, but also flu-like symptoms such as fever, chills and coughing, Shah said. All are recovering. The people infected after working with dairy cattle included one in Texas, two in Michigan and one on a dairy farm in Colorado.

The CDC told reporters it plans to modify its recommendations regarding personal protective equipment, given the very high temperatures. Shah said the CDC’s industrial hygienist who is now boots on the ground in Colorado “can help implement improved engineering controls that may make PPE use more uniform as well as more palatable.”

Avian flu vaccine, in case

The U.S. Department of Health and Human Services announced two weeks ago that it has contracted with Moderna to develop an mRNA-based pandemic influenza vaccine for bird flu under a contract worth about $176 million. “This award aids Moderna in ensuring the establishment of additional pandemic influenza vaccine response capability. These efforts will leverage existing U.S. domestic large-scale commercial mRNA-based manufacturing platforms and ongoing seasonal influenza vaccine development,” the announcement said.

Phase 1 safety trials are expected late in 2024. But public health officials say the vaccine-related activity is proactive; it does not mean that a vaccine will be recommended unless the situation and likelihood of spread to humans changes significantly.