Bird flu has infected six farm workers in Colorado this month — the most in any state — and health officials have stressed the importance of preparedness to control the H5N1 virus spreading in dairy herds and poultry flocks across the country.
During a news conference Tuesday, federal officials said temperatures rising above 104 degrees make it difficult for workers to wear the full-body suits, goggles and N95 masks needed to protect them from the virus.
Nirav Shah, principal deputy director of the Centers for Disease Control and Prevention, said, « There is no doubt that the sheds where the killings took place were still hot. Large industrial fans were used to cool the sheds, but they spread feathers around, which are known to carry the virus. The killing process was extensive with infected birds. Involving contact, workers must place chickens in carts where they are killed by carbon dioxide gas.
« It was difficult for workers to maintain a good seal or a good fit between the mask or with the eye protection, » Shaw said. « This confluence of factors may play a role in explaining why, where and when this outbreak occurred. »
A poultry farm in Weld County has put 160 workers on hold and will continue to do so for 10 to 14 days to prevent further spread among the flock, said Eric Teeble, the senior USDA official overseeing bird flu outbreaks. About 55 poultry workers with symptoms have been tested, Shah said. All but five workers did not have bird flu. Four have been confirmed by the CDC; A positive case is pending confirmation.
According to Colorado health officials, an additional 16 symptomatic poultry workers were tested Monday and are awaiting results.
Although more cases are being detected, the risk to the general public remains low, officials said.
Human infection is rare. All US human cases are linked Direct contact with infected cows or chickens – Authorities have said that it does not spread from person to person.
H5N1 bird flu is widespread in wild birds around the world and caused an outbreak in U.S. dairy cows for the first time this spring. Almost 160 dairy herds According to the U.S. Department of Agriculture, 13 states have been infected. This strain of highly pathogenic avian influenza is fatal to domestic poultry and can wipe out entire flocks within days. But it causes less severe disease in cows.
Colorado is one of the states hardest hit by the virus, with outbreaks At least 37 dairy herds, including several in Weld County where the poultry workers were Infected. Genetic sampling of the virus from chickens on the farm showed the same type of virus found in nearby infected dairy herds, USDA's Teeble said.
Earlier in July, a Colorado The milkman contracted bird flu For cattle infected with the virus. Authorities are investigating the link between the milk worker and the five poultry workers.
Across the United States, a total of nine people, including three other dairy workers — two in Michigan and one in Texas — have been infected with H5N1 this year.
Since birds shed flu viruses in their saliva, mucus and feces, direct exposure to infected birds increases the risk of infection. Dairy producers can become infected with the virus through contaminated milk or equipment.
Officials said the genome sequence of the virus from one of the infected chicken workers could provide more clues about how the virus was spread. Part of the virus is similar to what was found in the Texas worker and the first Michigan worker, Shaw said. One hypothesis is that infected dairy cows from Texas were transported to Michigan and Colorado.
« What happens in a few limited cases spreads over very tight regional or local areas, » Shaw said. « It also explains that the virus we saw was mostly the same, even though it originated in different geographic areas, from Michigan to Colorado. »
The CDC does not recommend that livestock workers be vaccinated against bird flu because all workers exposed to the disease reported mild symptoms. Poultry workers experienced common flu-like symptoms including fever, chills, cough, sore throat and runny nose, along with conjunctivitis and watery eyes, according to the CDC. No one was hospitalized.
The CDC has not identified any unusual flu trends in lab data or emergency department visits at the national, state or local levels, Shaw said.
Preliminary analysis of the genome sequence of the virus from a poultry worker in Colorado showed no changes in the virus It can increase the severity of the disease, facilitate person-to-person transmission or Tamiflu may reduce the effectiveness of treatment, Shaw said.
Federal health and agriculture officials have repeatedly emphasized the importance of precautions such as wearing personal protective equipment when working with infected animals. Central and state authorities have made the materials available to dairy farm owners but have not required their use.
Federal officials on Tuesday praised Colorado for its planning and response to the outbreak. In May, the state requested 5,000 goggles, 300,000 pairs of gloves and 150,000 N95 masks from the federal stockpile because dairy herds in the state were affected. Over the weekend, the government requested 500 courses of Tamiflu after five poultry workers tested positive for the virus. More than 150 workers infected with the infected poultry farm received antiviral drugs. State health officials reported worker infections to the CDC in real time, allowing the agency to send a 10-person bilingual team to help with the investigation.
Nahid Padelia, director of Boston University's Center for Emerging Infectious Diseases and a former senior adviser to the Biden administration's White House coronavirus response team, said infectious-disease experts worry about what will happen as the virus hits more people, increasing its chances. Can become contagious from person to person and cause more serious illness.
« So far, yes, the diseases are not that severe, » he said. « But it's only a matter of time before the disease finds someone with medical conditions that can create a difficult course. »
Colorado workers reported the first cases of H5N1 infection in poultry workers since April 2022, when a prison inmate killed chickens as part of a pre-release work program. There was an infection The same strain that causes bird flu to spread to dairy cows. The worker reported fatigue as the only symptom, was treated with Tamiflu, and recovered.
Correction
An earlier version of this article misspelled the name of Nahid Patelia, director of Boston University's Center for Emerging Infectious Diseases. The article has been corrected.
