Rare Drug-Resistant Flu Variant Detected in U.S.

The U.S. Centers for Disease Control and Prevention (CDC) has reported two human cases of influenza that are resistant to the most popularly antiviral flu medicine oseltamivir phosphate, known by the brand name Tamiflu.

While flu viruses are continually evolving, the CDC’s new infectious diseases report showed this variant contains two major mutations that derive from the most common version of seasonal flu called influenza A (H1N1), WebMD reported.

These concerning mutations could lower the effectiveness of treatment with Tamiflu, CNN reported. The mutated version of the flu virus was not resistant to newer, less used-antiviral drugs, such as baloxavir marboxil, which goes by the brand name Xofluza, the CDC said. In general, flu antiviral drugs have been shown to reduce the severity of the flu, and some studies have reported a link between taking these medicines and a lower risk of death for adults hospitalized with flu, WebMD said.

With active global surveillance for mutations, experts said the threat to humans remains low. Still, c, according to the CDC. However, the dual mutant flu variants cases remain infrequent, amounting to approximately 1% of the samples collected between May 2023 and February 2024.

Since October 2023, an estimated 35 million cases of flu have occurred in the U.S., resulting in 390,000 hospitalizations and 24,000 deaths, according to the CDC’s weekly FluView publication.