Influenza’s Simple Genome Packs a Wallop The Virology of Influenza, Part 1

(Card 1 of 2) Influenza is an ancient disease, and its name comes from the Italian word for “influence.” Centuries ago, it was believed that this constellation of symptoms (fever, myalgia, coryza, prostration, diarrhea, cough, and sometimes pneumonia or death) was caused by the influence of supernatural powers on humankind. Today, the source of influenza is well known. Influenza is a negative-sense stranded RNA virus. In fact, influenza comes in 2 main families, influenza A and influenza B, neither of which should be confused with the similarly named parainfluenza virus or the totally unrelated bacterium Haemophilus influenzae. Because it was originally isolated from the respiratory tracts of flu patients, H influenzae was thought, for a time, to be the cause of the flu, which we now know to be incorrect. Today, when we talk about the flu virus, we are referring to the influenza virus, especially influenza A. Influenza B is also a problem for humans and has the potential to make patients very sick. For this reason, the trivalent seasonal influenza vaccine always contains 1 influenza B antigen. However, influenza A is the main concern because it consistently makes up the great bulk of human infections. Influenza A: Influenza A’s genome is simple, consisting of just 8 genes. Two of the most important genes are for hemagglutinin (knob-like protein on virus’s surface that allows it to bind to respiratory epithelial cells) and neuraminidase (protein that allows new virions to bud from infected human cells, thus perpetuating the infection). Without both hemagglutinin and neuraminidase, influenza A would be rendered essentially harmless to human populations. The nomenclature of influenza A (H1N1, H3N2, etc) is based on the different combinations of antigens found on a given strain. (Reviewer-).