Experts say they’re increasingly alarmed about the spread of a highly parthenogenic strain of the bird flu, or avian influenza, that’s showing signs of mutating to be more contagious to humans.
The virus, known as H5N1, was first detected in migratory birds in the U.S. in January 2022, and since has been detected in wild birds in all 50 states and more than 1,300 commercial poultry flocks across the country. Now, it is showing up in cattle herds, swine and other animals.
The Wild Felid Advocacy Center in Shelton, Washington, issued a statement on Facebook recently, saying 20 large cats at the facility had died from the virus. Several others contracted the virus but survived.
“We are heartbroken to share that animal health officials have confirmed the presence of highly pathogenic avian influenza (HPAI) among over half of our wild felids as of December 2024,” the statement said, adding that cats are particularly vulnerable and can die within 24 hours from pneumonia-like symptoms.
Dr. Amesh Adalja, of the Johns Hopkins Center for Health Security, told MedPage Today the federal government hasn’t taken sufficient action against the outbreak, predicting the situation is likely to get worse in 2025.
“In September we were still in the 20s in terms of human cases, and now we’re in the 60s,” the doctor said.
Recent news doesn’t indicate a pandemic is inevitable, “but it means the virus is starting to find its way into humans and potentially tune itself to being a human pathogen,” Dr. Adalja said.
As of December 30, 66 cases in humans had been confirmed, with a severe Louisiana case triggering concerns the virus was mutating to make it more transmissible. Forty of the cases were linked to poultry or dairy operations.
“Deep sequencing of the genetic sequences from two clinical specimens from the patient in Louisiana was performed to look for changes associated with adaptation to mammals,” the Centers for Disease Control and Prevention said, adding, differences were found in the genome when compared to the strain in the Louisiana man’s flock, “suggesting [the changes] emerged during the clinical course as the virus replicated in the patient.”
Experts worry if a patient contracts both H5N1 and seasonal flu at the same time, the viruses could swap genes.
“If there are all these people getting infected, that provides so many opportunities for the virus to better adapt,” Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan, told The New York Times. “It has the potential to really harm a lot of people.”
“The traffic light is changing from green to amber,” said Dr. Peter Chin-Hong, a professor of medicine at the University of California, San Francisco.
“Many signs are going in the wrong direction,” Dr. Chin-Hong told NBC.
A study published in the journal Science found a single mutation in the strain found in cows could make the virus, which historically has had a 30% mortality rate for humans, highly contagious.
The USDA has detected the virus in milk, prompting the agency to push for testing of dairy cattle – 901 herds in 16 states have tested positive so far. In California, more than 70% of herds have been infected.
In early December, the USDA’s Animal and Plant Health Inspection Service (APHIS) announced a nationwide milk testing program. The federal order requires the sharing of raw milk samples upon request and requires the mandatory testing of lactating cows before they can be shipped interstate.
As for poultry operations, APHIS said those seeking compensation for losses will have to undergo a biosecurity audit before restocking.
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