Skip to main content

'Dual Mutant' Seasonal Flu Virus Could Make Some Treatments Ineffective

Medically reviewed by Carmen Pope, BPharm. Last updated on June 13, 2024.

By Robin Foster HealthDay Reporter

THURSDAY, June 13, 2024 -- Two human cases of "dual mutant" strains of H1N1 flu have been reported by U.S. health officials.

Unfortunately, the genetic changes appear to render the leading flu antiviral, Tamiflu, less effective, researchers from the U.S. Centers for Disease Control and Prevention noted.

The new analysis, published Wednesday in the agency's Emerging Infectious Diseases journal, describes these two concerning mutations -- which scientists have dubbed I223V and S247N.

The latest finding follows a report published last March in the Lancet journal by Hong Kong scientists that found the two mutations seemed to raise resistance to the flu treatment oseltamivir (Tamiflu).

Lab tests found the mutated flu viruses were up to 16 times less sensitive to the antiviral, a smaller drop-off than in some previous worrying mutations, reported researchers led by Mira Patel, a senior scientist at the CDC.

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

"These mutated viruses retained sensitivity to other anti-influenza medications, including a newer one, baloxavir marboxil. There are no immediate implications to change decisions for clinical care," a CDC spokesperson told CBS News, and vaccination still offers protection against mutated viruses.

Despite the "rapid spread of dual mutants to countries on different continents," the CDC report added that these new flu strains are still rare for now.

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

The two U.S. cases were detected by labs at the Connecticut Department of Health and University of Michigan this past fall and winter.

"It is unknown how widely these mutated viruses will circulate in the upcoming season. It is important to continue monitoring 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 found the drug made up 99.8% of flu antivirals prescribed to kids.

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

Sources

  • Emerging Infectious Diseases, June 12, 2024
  • CBS News

Disclaimer: Statistical data in medical articles provide general trends and do not pertain to individuals. Individual factors can vary greatly. Always seek personalized medical advice for individual healthcare decisions.

© 2025 HealthDay. All rights reserved.

Posted June 2024

Read this next

HHS Announces Plans to Pay Moderna $176 Million for mRNA Flu Vaccine

FRIDAY, April 25, 2025 -- On Tuesday, the U.S. Department of Health and Human Services announced that the government will invest $176 million in Moderna to expedite the creation...

California Gives $25 Gift Cards To Boost Bird Flu Testing

FRIDAY, April 25, 2025 — Health officials in California are now offering gift cards to encourage folks near farms to get tested for bird flu. The project is a partnership...

Experts Warn Bird Flu Could Pose Growing Risk to Human Health

SATURDAY, April 5, 2025 -- Bird flu is changing fast and could become more dangerous to humans, new research from the University of North Carolina at Charlotte suggests. A team...

More news resources

Subscribe to our newsletter

Whatever your topic of interest, subscribe to our newsletters to get the best of Drugs.com in your inbox.