Two New Drug-resistant 'Dual Mutant' H1N1 Flu Strains Found In The US; CDC Says Is Tracking Them

At least two human cases of the new "dual mutant" strains of H1N1 influenza have been detected in US patients, the Centers for Disease Control and Prevention said, with genetic changes that could cut the effectiveness of the main flu antiviral that hospitals rely on. An analysis of the new H1N1 flu viruses with these two concerning mutations – which scientists call I223V and S247N, describing changes to key surface proteins of the virus – was published this week in the agency's Emerging Infectious Diseases journal. Read on to know.
Drug resistant dual mutant flu strains in US

There has been a growing concern over the new H1N1 flu viruses with mutations

The Centers for Disease Control and Prevention has said it is tracking at least two human cases of the new "dual mutant" strains of H1N1 influenza, with genetic changes that could cut the effectiveness of the main flu antiviral. There has been a growing concern over the new H1N1 flu viruses with mutations, called I223V and S247N with changes to key surface proteins of the virus. These changes were published in the agency's Emerging Infectious Diseases journal.
In March this year, scientists from Hong Kong had first published the report after first testing these mutations. Their lab experiments found that the two mutations appeared to raise H1N1's resistance to the flu treatment oseltamivir - commonly sold under the brand Tamiflu by drugmaker Roche.
According to experts, it is still unclear how much the mutations could cut the real-world effectiveness of oseltamivir. The laboratory tests found the mutated viruses were up to 16 times less sensitive to the antiviral, a smaller drop-off than in some previous worrying mutations.
"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," CDC told CBS News.

Mutations first appeared last year

Since the mutations first appeared in May 2023, many cases have been reported from 15 countries across five continents. At least more than a 100 virus samples have to date been shared with the global virus database GISAID from countries across Africa, Asia, Europe, North America, and Oceania.
The two countries with the highest number of reported cases include the Netherlands, with 30 reported cases, and France, with 24 reported cases. However, these mutations are still considered rare, making up less than 1 per cent of flu virus sequences globally.
In the US, two cases were detected by labs at the Connecticut Department of Health and University of Michigan this past fall and winter.

Flu season approaching

Experts say with the upcoming flu season, it is still unclear how the newly mutated viruses will spread, but doctors say flu vaccination remains important as it still offers protection.
The CDC also emphasizes the importance of early antiviral treatment for hospitalized flu patients and those at risk of severe illness. They say will continue to monitor and track any new spread and genetic changes. "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 wrote on its website.
The swine flu pandemic had grappled across the world in 2009 before it was wiped off the map by a competing H1N1 strain. Health authorities from Europe to Japan had reported seeing surges of a H1N1 strain that was resistant to oseltamivir in 2007 and 2008.
That strain had a mutation called H275Y, which at the time was up to 1,000 times less sensitive to oseltamivir in laboratory tests.
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