Temperatures soared to more than 104 degrees, making it difficult for workers to wear the full-body protective gear, goggles and N95 masks needed to protect against the virus, federal officials said at a news conference Tuesday.
“It was definitely hotter in the houses where the culling took place,” said Nirav Shah, principal deputy director at the Centers for Disease Control. Large industrial fans were used to cool the houses, but they also spread feathers that are known to carry the virus, he said. The culling method involved frequent contact with infected birds, and required workers to load the birds into carts that kill them with carbon dioxide gas.
“Workers found it difficult to maintain a good seal or fit with both masks and eye protection,” Shah said. “This combination of factors may help explain why, where and when this outbreak occurred.”
Eric Deeble, a senior U.S. Department of Agriculture official overseeing avian flu efforts, said the cull at the Weld County poultry plant involves 160 workers and is expected to continue for another 10 to 14 days to prevent further spread of the disease among birds. About 55 symptomatic poultry workers have been tested, Shah said. All but five have tested negative for avian flu. Four have been confirmed by the CDC, and one presumptive positive case is pending confirmation.
Colorado health officials said 16 more poultry workers with symptoms were tested Monday and are awaiting results.
Officials said it was possible more cases would be discovered, but the risk to the public remained low.
Human infections are rare. All human cases in the United States Direct contact with infected cattle or poultry Officials say there is no person-to-person transmission.
H5N1 avian influenza is spreading among wild birds around the world and was first detected in dairy cows in the United States this spring. Almost 160 dairy cows The highly pathogenic avian influenza virus, which has been confirmed in 13 states, is deadly to poultry and can wipe out entire flocks within days, but doesn’t cause as severe an illness in cattle.
Colorado has been one of the states hardest hit by the virus. At least 37 dairy herds were killed, including one in Weld County where poultry workers were located. Genetic samples of the virus taken from chickens on the farm showed it was the same type found in a nearby herd of infected dairy cows, USDA’s Deeble said.
In early July, Colorado Dairy workers infected with bird flu A cow has been confirmed to be infected with the virus, and authorities are investigating whether there is a link between the dairy worker and five poultry workers.
Nine people across the United States have been infected with the H5N1 virus this year, including three dairy workers, two in Michigan and one in Texas.
Birds shed influenza viruses in their saliva, mucus and excrement, so direct contact with infected birds increases the risk of infection. Dairy workers can become infected with the virus through contaminated milk or equipment.
Genetic sequencing of the virus taken from one of the infected poultry workers may provide further clues about how the virus is spreading, officials said. Part of the virus is the same as that found in the Texas worker and the first worker in Michigan, Shah said. One hypothesis is that infected dairy cows from Texas were transported to Michigan and Colorado.
“What’s happening in the few cases could be spreading within a very small geographic area or region,” Shah said, “and that could explain why the virus we’re seeing is broadly the same, even though it’s occurring in a variety of locations from Michigan to Colorado.”
The CDC does not recommend vaccinating against bird flu because all of the infected livestock workers had mild symptoms. The poultry workers experienced typical flu symptoms, such as fever, chills, cough, sore throat and runny nose, as well as irritated and watery eyes, according to the CDC. No one was hospitalized.
Shah said the CDC has not identified any unusual flu trends in testing data or emergency department visits at the national, state or local level.
Preliminary analysis of the genetic sequence of the virus from the Colorado poultry workers showed no changes in the virus. They can increase the severity of the disease, make it easier for people to spread, Shah said it could make the Tamiflu treatment less effective.
Federal health and agriculture officials have repeatedly stressed the importance of precautions such as wearing personal protective equipment when handling infected animals. Federal and state authorities have provided dairy farmers with protective equipment but have not mandated its use.
Federal officials on Tuesday praised Colorado’s planning and response to the outbreak. After dairy farmers in the state were infected in May, the state requested 5,000 goggles, 300,000 pairs of gloves and 150,000 N95 masks from the federal stockpile. Over the weekend, the state requested 500 doses of Tamiflu after tests showed five poultry workers had the virus. More than 150 workers who may have come into contact with the infected poultry have been given the antiviral drug. State health officials also notified the CDC of worker infections in real time, allowing the agency to send a 10-person bilingual team to assist with investigations.
Nahid Bhadelia, director of the Center for Emerging Infectious Diseases at Boston University and a former senior adviser to the Biden administration’s White House coronavirus task force, said infectious disease experts are concerned about what could happen as the virus becomes more common and mutates to become more transmissible from person to person and potentially cause more severe illness.
“Right now, the disease is not very severe,” she said, “but it’s only a matter of time before we find someone with a condition that could cause the disease to take a more severe course.”
The Colorado worker is the first case of H5N1 infection among poultry workers since April 2022, when prison inmates were tasked with slaughtering poultry as part of a pre-release employment program. Infected He was infected with the same strain that caused an outbreak of avian flu among dairy cows. The worker reported feeling fatigued as his only symptom and was treated with Tamiflu and recovered.
Fixes
An earlier version of this article misspelled the name of Nahid Bhadelia, director of the Center for Emerging Infectious Diseases at Boston University. The article has been corrected.
