CDC Says "Mutant" Flu Strains Have Been Detected in U.S.—And Drugs May Not Help
The agency has just released a new report about concerning mutations.
After dealing with the COVID pandemic, you might not find yourself too worried about the flu—especially given that we've been battling influenza viruses for decades now through flu shots and prescription antiviral drugs. But new research from the Centers for Disease Control and Prevention (CDC) might be cause for concern, as the agency says "mutant" flu strains that may bypass those drugs have now been detected in the U.S.
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Back in March, Hong Kong scientists published a study in The Lancet journal detailing lab experiments on new H1N1 flu viruses with two concerning mutations: I223V or S247N. According to the study, these mutations appear to increase H1N1's resistance to oseltamivir, an antiviral commonly sold under the brand name Tamiflu.
These mutations first appeared in May 2023 with a case in the Canadian province of British Columbia, CBS News reported. And the rise of flu strains with one or both of these mutations continued to increase globally last fall, according to the Hong Kong study.
But now, a new analysis from the CDC, which was published June 12 in the journal Emerging Infectious Diseases, is confirming that these "dual mutant" flu strains have been detected within the U.S.
The agency's report indicates that at least two cases were confirmed in the country at the end of last year—one in Connecticut during October and the other in Michigan during December. Researchers said the "overall detection frequency" of these dual mutant strains is low, but the potential for it to increase in the future is still there.
"It is unknown how widely these mutated viruses will circulate in the upcoming season," a CDC spokesperson told CBS News. "It is important to continue monitoring the spread of these viruses and the evolution of these viruses."
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As CBS News further explains, it is not certain how much these two mutations could diminish the real-world effectiveness of oseltamivir drugs. The Hong Kong scientists determined that the mutated viruses were up to 16 times less sensitive to this antiviral, but their research was only conducted in laboratory test settings.
The CDC's new report also indicates that other approved influenza antiviral drugs were still effective against the dual mutant strains.
"These mutated viruses retained sensitivity to other anti-influenza medications, including a newer one, baloxavir marboxil," the CDC spokesperson told CBS News. "There are no immediate implications to change decisions for clinical care."
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