April 24, 2024 – Particles of the bird flu virus recently found in dairy cattle have been detected in pasteurized milk, but the nation’s milk supply remains safe to drink and the CDC has taken key steps toward making a vaccine in case one is needed, federal officials announced Tuesday.
Known as H5N1 avian influenza, tiny bits of the virus aren’t expected to be removed from milk during a treatment process called pasteurization, the FDA said in an advisory, adding that the agency is doing a variety of further tests, including to see if the virus is able to replicate in laboratory conditions.
The agency affirmed it’s still safe to consume milk, stating that “based on the information currently available, our commercial milk supply is safe because of these two reasons: 1) the pasteurization process and 2) the diversion or destruction of milk from sick cows.”
Symptoms in infected cattle have included decreased lactation and low appetite, according to the advisory.
Pasteurization is a process of heating milk for a prolonged period to kill bacteria and viruses. The FDA said its further test results should be ready in “the next few days to weeks.”
David O’Connor, PhD, a virologist at the University of Wisconsin-Madison, told The New York Times that people who drink milk containing viral fragments are unlikely to get sick.
“The risk of getting infected from milk that has viral fragments in it should be nil,” he told the Times. “The genetic material can’t replicate on its own.”
Bird flu is widespread in wild birds and sometimes affects commercial poultry flocks. It is being documented in more animals, with cattle being the latest addition to the list.
Earlier this year, a Texas cattle farmer was confirmed to have been infected with bird flu. His main symptom was pink eye, and he recovered.
On Tuesday, the CDC posted an update on its bird flu webpage stating that antiviral drugs were effective against the flu strain that infected the cattle farmer, and the “CDC has already made a candidate vaccine virus (CVV) that could be used to make a vaccine if needed.”
Bird flu grabbed headlines in 1997, when 18 human cases were documented in Hong Kong. The infections were linked to poultry, and six people died. The unique strain of the virus was eliminated “through total depopulation of all poultry markets and chicken farms in December 1997,” according to a scientific paper published in 2003 about the outbreak.
Since 1997, humans have been infected with strains of bird flu in 23 countries, according to the CDC, and more than 50% of those people infected died. Bird flu is present in wild birds in all 50 U.S. states, and most states have also had confirmed infections in commercial or backyard poultry flocks in the past 2 years, the CDC says. Along with the Texas cattle farmer, there was another U.S. human case, which was linked to contact with poultry in Colorado in 2022.
In partnership with the CDC, FDA officials said they are monitoring data from emergency rooms and flu test results “for any unusual trends in flu-like illness, flu, or conjunctivitis,” which is also called pink eye.
Federal officials have published genetic information from recent bird flu strains “in the interest of public transparency and ensuring the scientific community has access to this information as quickly as possible to encourage disease research and development to benefit the U.S. dairy industry,” the U.S. Department of Agriculture announced this week.