Outbreaks are ongoing HPAI has devastated poultry and wild bird populations across the United States and around the world. The virus, known as H5N1, is also increasingly adapting to mammals and has been found in cats, goats and raccoons. In the United States, it has spread to at least 170 dairy herds across 13 states. And in April, health officials confirmed that a dairy worker had contracted the virus from an infected cow. It was the first time the virus made the leap from mammal to human.
The number of people infected with bird flu is increasing. On July 25, the US Centers for Disease Control and Prevention Three more human cases confirmedbringing the total number of cases in the United States to 13 since April. The infections occurred in people who worked directly with infected poultry at an egg farm in Colorado, which reported an H5N1 outbreak in its poultry flock. All three people had mild symptoms and were given Tamiflu, an antiviral drug. The CDC said the risk of H5N1 infection in the general public remains low.
“These cases are not entirely surprising, given that these people work with infected poultry,” said Stephen Morse, an epidemiologist at Columbia University in New York. “The good news is that there is no evidence of human-to-human transmission so far. At that point, we really have to raise the red alert level to a level of concern.”
The CDC is looking into whether the workers in Colorado were wearing personal protective equipment, or PPE, such as gloves, gowns, footwear, masks, and goggles. Historically, most human cases of avian influenza have occurred in people who were not wearing recommended PPE, the agency said.
The new cases come on the heels of another cluster of human infections identified earlier this month. On July 19, the CDC confirmed six human cases of avian influenza among poultry workers at another Colorado facility. Those cases were among workers involved in culling birds infected with H5N1. When the virus is detected on a farm, poultry farmers are required to cull the entire flock. With the three latest cases, Colorado now has nine confirmed cases of avian influenza.
The remaining four cases—one in Texas, two in Michigan, and one in Colorado—were linked to contact with infected dairy cows. The virus likely spread to workers through raw milk. A The study was published in May. found that the virus can remain stable on milking equipment for at least an hour, increasing the likelihood of infection to humans and other animals. However, pasteurization of milk can kill the H5N1 virus.
So far, all cases in the United States this year have had mild symptoms, but in the past, H5N1 has caused mortality rate about 50 percentFrom 2003 to 2023, a total of 878 people tested positive for the virus and 458 deaths were reported.
The last time H5N1 caused a major outbreak in poultry in the United States was in 2015, when it killed 50.5 million birds. It wasn’t until April 2022 that the United States reported its first human case of bird flu, in a poultry worker in Colorado. No more cases have been reported since this year. “Something has changed,” said Anice Lowen, an influenza researcher at Emory University in Atlanta, Georgia. “It’s hard to know without more information whether it’s due to a change in the virus or a change in exposure circumstances.”
