The Centers for Disease Control and Prevention (CDC) said Wednesday that it was tracking two new cases of H1N1 influenza in the United States that are more resistant to medication.
The CDC published the new information in its Emerging Infectious Diseases journal, where it said the mutations, called I223V and S247N, are of public health concern.
The new flu strains were first reported by CBS News.
It follows a report by scientists in Hong Kong who conducted tests and found the new strains were more resistant to the flu treatment oseltamivir, commonly sold under the brand name Tamiflu.
The new strains also retained sensitivity to other antiflu medications, but as it stands, there is no change to clinical care for the mutated virus, a CDC spokesperson said in an emailed statement.
The CDC noted that the flu vaccine offers protection from the illnesses “with or without these mutations.”
The two U.S. cases were detected in labs at the Connecticut Department of Health and at the University of Michigan this past fall and winter. The mutations have been in global circulation since May 2023, but detection frequency was low, according to the CDC.
The CDC said it’s not known how widely the new viruses will circulate in the upcoming flu season, but it’s “important to continue monitoring the spread of these viruses and the evolution of these viruses.”
The 2009 swine flu pandemic was caused by the H1N1 virus, and according to the World Health Organization, there was a confirmed 491,382 cases and 18,449 deaths globally during the outbreak.
