At least two human cases of the new so-called "dual mutant" strains of H1N1 influenza have been detected in U.S. patients, the Centers for Disease Control and Prevention said Wednesday, with genetic changes that could cut the effectiveness of the main flu antiviral that hospitals rely on.
An analysis of the new H1N1 flu viruses with these two concerning mutations – which scientists call I223V and S247N, describing changes to key surface proteins of the virus – was published this week in the agency's Emerging Infectious Diseases journal. It follows a report by scientists from Hong Kong who first tested the mutations. Their lab experiments, published in March , found the two mutations appeared to raise H1N1's resistance to the flu treatment oseltamivir, commonly sold under the brand Tamiflu by drugmaker Roche.
It is unclear how much the mutations could cut the real-world effectiveness of oseltamivir. A CDC spokesperson was not able to immediately comment on the new report. Cases on multiple continents Despite the "rapid spread of dual mutants to countries on different continents," the CDC's report on the new dual mutant flu strains found the mutations appear to still be rare for now.
Since the mutations first showed up in a case sampled from the Canadian province of British Columbia in May 2023, a total of 101 sequences have been submitted to the global virus database GISAID from Africa, Asia, Europe, North America and Oceania. These make up less than 1% of flu virus sequen.
