H3N2 Dominates US

Flu season is well underway, and as of late one particular strain of influenza A has pushed itself to the top.  According to the MMWR (Morbidity and Mortality Weekly Report) from the CDC, there has been 566 documented cases of hospitalizations in the US, where most of the patients were above 65 years of age, suggesting that older people are more at risk of developing severe symptoms from the flu. The particular strain that was observed to be dominantly present in these individuals was the H3N2 strain. Moreover, in lab, a total of 135, 202 specimens were tested, where 3.7% were tested positive for influenza, where 73.4% tested positive for influenza A, and furthermore where 90% of the influenza A was the H3N2 strain. Of course, the flu season is not even close to over, so these percentages may well be subject to change along with the H3N2 strain being the current dominant strain. The CDC believes that data from the US will be the best indicator of how the flu will behave this season, and it should be noted that last year, a H3N2 component that was used in the previous flu season vaccine was 32% effective against the strain H3N2.

MD Dugan it should be noted that the current H3N2 strain is less antigenically similar than the H3N2 strains utilized for the production of a component of the flu vaccine. The reason for this discrepancy can be explained through the nature of influenza A viruses themselves, where what is called genetic drift caused by the accumulation of point mutations on the virus occurs, leading to slight changes in the neuraminidase and hemagglutinin receptors. This change in the receptors thus makes the vaccine less effective.


All in all, the reality of the matter is that the worst is yet to come, so brace yourselves, because we are in for a flutastic season.

Sources:

-Daniel Gutierrez
  

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