CDC Issues New Warnings About Evolving ‘Dual Mutant’ Flu Virus

By: Sam Watanuki | Published: Jun 14, 2024

The CDC has raised alarms about a new “dual mutant” H1N1 strain, identified as I223V and S247N. First detected in May 2023, these mutations have spread across 15 countries.

Researchers are particularly concerned because these strains show resistance to Tamiflu, a common antiviral medication used to treat the flu.

Global Spread and Detection

Since its initial discovery, the mutant strains have circulated globally, with higher prevalence in Europe. In the U.S., at least two human cases have been confirmed.

A woman coughing into her hand while she sits on a couch.

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The dual mutant virus has been found in 101 samples, according to the CDC’s publication in the Journal of Emerging Infectious Diseases.

Impact on Treatment Options

The resistance to Tamiflu is alarming, especially since this medication is crucial for treating high-risk groups and the elderly.

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The CDC notes that while these strains are resistant to Tamiflu, they remain susceptible to other antiviral drugs like baloxavir. This highlights the need for alternative treatments.

Expert Insights on the Mutation

Dr. Marc Siegel from NYU Langone Medical Center emphasized the unusual timing of the flu’s spread, noting that flu season typically ends by March.

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He expressed concerns about the reduced effectiveness of Tamiflu but still recommends its use for its partial benefits and suggests considering other anti-flu drugs.

Historical Context and Evolution

The dual mutant strains I223V and S247N were first tested by Hong Kong scientists and published in The Lancet Microbe in March 2024.

With a temperature of 103.8, Asa Moore, 6, of Vivian, Louisiana is examined by John Messier, a physician's assistant, at the North Caddo Surgical and Medical Center for symptoms of Influenza December 12, 2003 in Vivian, Louisiana. Moore had not received a flu shot and the medical center was out of the vaccine.

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These strains have shown to lessen the effectiveness of Tamiflu, underscoring the importance of continuous monitoring and research to understand their evolution.

CDC's Ongoing Surveillance

The CDC’s study shows the importance of closely monitoring these dual mutants. Researchers warn that additional changes in the virus could further affect drug susceptibility or give the virus an advantage over wild-type strains.

This photograph depicts an exterior view of CDC′s Roybal campus in Atlanta, GA


Continuous surveillance is key to staying ahead of these mutations.


Vaccination Recommendations

Despite the challenges posed by these new strains, the CDC continues to recommend annual flu vaccinations for everyone aged six months and older.

A doctor wearing a white coat and blue gloves opening a syringe.

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Vaccinations remain a critical tool in preventing the spread of the flu and reducing the severity of symptoms in infected individuals.


Current Flu Season Statistics

The 2024 flu season has been significant, with the CDC estimating at least 35 million flu-related illnesses, 390,000 hospitalizations, and 24,000 deaths.

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These statistics highlight the importance of vaccination and effective treatment options to manage flu outbreaks.


Future Research Directions

Ongoing research is crucial to developing new antiviral medications and vaccines that can effectively combat evolving flu strains.

A researcher using a scientific microscope.

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The CDC and global health organizations are committed to studying these mutations to ensure public health safety and preparedness.


Public Health Advice

Health experts advise the public to stay informed about flu developments and follow CDC guidelines, including getting vaccinated and considering antiviral medications if infected.

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High-risk groups such as immuno-compromised and elderly individuals should be particularly vigilant in protecting themselves against the flu.


Preventive Measures

Beyond vaccination, preventive measures such as frequent hand washing, wearing masks in crowded places, and maintaining good hygiene can help reduce the spread of the flu.

Person getting a flu shot while several other wait in line

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Public awareness and proactive behavior are essential in managing flu seasons effectively.


Staying Vigilant

The emergence of the dual mutant H1N1 strains underscores the dynamic nature of flu viruses and the need for continuous vigilance.

A person wears a mask to protect against the pandemic.

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The CDC’s warnings highlight the importance of staying informed, getting vaccinated, and supporting ongoing research to combat these evolving threats effectively.