Dual Mutant Flu Virus May Render Treatments Ineffective

On Thursday, June 13, 2024, U.S. health officials disclosed that two human cases of "dual mutant" strains of H1N1 flu have been identified. These new strains exhibit genetic alterations that appear to reduce the effectiveness of Tamiflu, a leading flu antiviral medication.

The U.S. Centers for Disease Control and Prevention (CDC) reported these findings in their journal, Emerging Infectious Diseases, highlighting two specific mutations named I223V and S247N. This discovery builds on research published in March in the Lancet journal by scientists from Hong Kong, who found that these mutations increase resistance to the flu treatment oseltamivir, commonly known as Tamiflu.

Laboratory tests indicate that these mutated viruses are up to 16 times less sensitive to oseltamivir, although this drop in sensitivity is not as severe as seen in previous mutations. According to Mira Patel, a senior scientist at the CDC, the agency is not overly concerned at this stage.

A CDC spokesperson emphasized that the mutated viruses continue to respond to other anti-influenza medications, including the newer drug baloxavir marboxil. Therefore, there are no immediate changes needed in clinical care decisions, and vaccinations still provide protection against these mutated strains.

Despite the rapid international spread of these dual mutants, the CDC report notes that the new flu strains remain relatively rare. Since the first detection in May 2023 from a case in British Columbia, Canada, 101 sequences have been uploaded to the global virus database GISAID. These sequences have been reported from regions in Africa, Asia, Europe, North America, and Oceania.

In the United States, the two cases were detected by laboratories at the Connecticut Department of Health and the University of Michigan during the past fall and winter seasons.

The CDC spokesperson pointed out the uncertainty surrounding the circulation of these mutated viruses in the upcoming flu season. Continuous monitoring of their spread and evolution is crucial.

The CDC also noted that Tamiflu is the most commonly prescribed flu treatment. A study published last year in the journal Pediatrics found that Tamiflu accounted for 99.8% of flu antivirals prescribed to children. Additionally, doctors have been using Tamiflu to treat humans infected during an ongoing outbreak of bird flu in dairy farms this year.

In summary, while the emergence of these dual mutant strains of H1N1 flu is concerning due to their reduced sensitivity to Tamiflu, other antiviral medications remain effective, and current vaccinations still offer protection. The situation underscores the importance of ongoing surveillance and research to adapt to evolving flu viruses.