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Scientists Dig into Influenza’s Biggest Mystery

It’s a puzzling flu riddle straight from Medicine’s X-Files: How do the smallest flu threats sometimes pack the biggest and sickliest punch?

Scientists have found minor variants of flu strains not typically targeted on vaccines carry a more potent viral punch than previously realized, Medical News Today reported in early January 2016.

Authors of the paper, which appears in the journal Nature Genetics, studied samples from the 2009 Hong Kong flu epidemic. Their research determined that these minor strains are transmitted along with major strains and can replicate and elude immunizations. The bad news: None of these minor flu strands are included in this season’s vaccine formulas.

“A flu virus infection is not a homogeneous mix of viruses, but, rather, a mix of strains that gets transmitted as a swarm in the population,” said Elodie Ghedin, a professor in New York University’s Department of Biology and College of Global Public Health and a co-author of the study, told MNT. “Current vaccines target the dominant strains, because they are the ones that seem to infect the largest number of individuals. But our findings reveal an ability of minor strains to elude these vaccines and spread the virus in ways not previously known.”

The Influenza A virus has long been marked by a high level of genetic diversity. However, our efforts to fight Influenza A largely stem from the dominant strain, which vaccines target. The trouble minor strands poise to scientists is their still much mysterious ability to spread the virus between people.

Examining the confirmed 2009 Hong Kong flu cases and their household contacts through whole genome deep sequencing of upper nasal cavity swabs, Ghedin and her team were able to identify variants in flu strains and also quantify what was being transmitted between infected individuals.

Their results displayed that, as expected, most 2009 Hong Kong cases carried the dominant flu viruses – H1N1 and H3N2. But they also carried minor strains and variants of the major and minor strains, which easily transmitted across the board in the studied individuals.

“The combination of unique data, sequencing approaches and mathematical methods create a nuanced picture of the transmission of diversity during a pandemic,” said study co-author Benjamin Greenbaum, an assistant professor at the Tisch Cancer Institute at the Icahn School of Medicine at Mount Sinai.

Added Ghedin: We were able to look at the variants and could link individuals based on these variants.

“What stood out was also how these mixes of major and minor strains were being transmitted across the population during the 2009 pandemic — to the point where minor strains became dominant.”

Experts note the study’s findings further confirm the importance of one of the most proven flu prevention methods: Smart hand hygiene practices (including frequent handwashing with soap and water and regular use of hand sanitizer). It’s the one guaranteed influenza stopper for both major and minor flu strands that we have at the ready every flu season.

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