Meet Influenza Virus!
Chances are you’ve caught “the flu” at some point in your life. There are 4 species of influenza viruses – A, B, C, and D.
The influenza virus is a 80-120nm, spherical, enveloped virus carrying an 8-segment RNA genome. Influenza Virus A and B (IAV and IBV) both contain hemagglutinin (HA), neuraminidase (NA), and M2 protein in the viral envelope. ICV and IDV contain a hemagglutinin-esterase fusion in the envelope. Just inside the viral envelope is a matrix protein capsid. This capsid protects 8 RNA segments each bound to a ribonucleoprotein (RNP) complex including an RNA polymerase.
Influenza virus has an incubation period of about 1-4 days and results in symptoms such as fever, chills, headaches, muscle pain, fatigue, cough, sore throat, and nose congestion.
Importantly, influenza viruses are very capable of antigenic drift, which is the gradual accumulation of mutations. Antigen drift is especially common in the HA protein, in which only a few mutations can lead to the evasion of pre-existing immunity. This propensity for antigenic drift is what constitutes a yearly vaccination, which is updated each year to provide protection against an H1N1 strain (IAV), an H3N2 strain (IAV), and one or two IBV strains. The WHO meets 2x a year, to look at hemispheric data and determine which strains should be included. The effectiveness of the flu vaccine averages 50-60%.
Posted on Instagram on April 9, 2021.