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The ‘dual mutant’ seasonal flu virus could make some treatments ineffective




The 'dual mutant' seasonal flu virus could make some treatments ineffective

Two human cases of “double mutant” strains of H1N1 flu have been reported by US health officials.

Unfortunately, the genetic changes appear to make the main flu antiviral drug, Tamiflu, less effective, researchers at the U.S. Centers for Disease Control and Prevention noted.

The new analysis, published in the agency on Wednesday Emerging infectious diseases magazine describes these two mutations in question – which scientists have named I223V and S247N.

The latest finding follows a report published in the newspaper last March Lancet journal of Hong Kong scientists who found that the two mutations appeared to increase resistance to the flu treatment oseltamivir (Tamiflu).

Lab tests showed that the mutated flu viruses were up to 16 times less sensitive to the antiviral drug, a smaller drop than some previous worrisome mutations, researchers led by Mira Patel, a senior scientist at the CDC, reported.

Still, the agency isn’t hitting the panic button at this point.

“These mutated viruses retained their sensitivity to other anti-flu drugs, including a newer one, baloxavir marboxil. There are no immediate implications for changing clinical care decisions,” a CDC spokesperson told CBS News, and vaccination still provides protection against mutated viruses.

Despite the “rapid spread of double mutants to countries on several continents,” the CDC report added that these new flu strains are still rare for now.

Since they were first spotted in a case from the Canadian province of British Columbia in May 2023, 101 sequences from Africa, Asia, Europe, North America and Oceania have been submitted to the global virus database GISAID, CBS News reported.

The two U.S. cases were discovered last fall and winter by laboratories at the Connecticut Department of Health and the University of Michigan.

“It is unknown how widely these mutated viruses will circulate in the coming season. It is important to continue to monitor the spread of these viruses and the evolution of these viruses,” the CDC spokesperson said.

Tamiflu is the most commonly prescribed flu treatment, according to the CDC. A study published in the journal Pediatrics Last year it emerged that the drug made up 99.8% of flu antivirals prescribed to children.

Doctors have also turned to Tamiflu to treat people infected during an ongoing outbreak of bird flu on dairy farms this year, CBS News reported.

More information:
Mira C. Patel et al, Spread of influenza A(H1N1)pdm09 viruses in multiple countries with reduced inhibition of oseltamivir, May 2023 – February 2024, Emerging infectious diseases (2024). DOI: 10.3201/eid3007.240480

Rhoda Cheuk-Ying Leung et al., Global emergence of neuraminidase inhibitor-resistant influenza A(H1N1)pdm09 viruses with I223V and S247N mutations: implications for antiviral resistance monitoring, The Lancet bug (2024). DOI: 10.1016/S2666-5247(24)00037-5

The CDC has more on the flu.

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