influenzaviruksen

Influenzavirus is a genus of negative-sense, single-stranded RNA viruses belonging to the family Orthomyxoviridae. These viruses are responsible for causing influenza, commonly known as the flu, in humans and other animals. The genome of influenzaviruses is segmented, typically consisting of eight RNA segments, each encoding one or more proteins.

There are four main types of influenza viruses: A, B, C, and D. Influenza A viruses are found in a wide range of animals, including birds, pigs, and horses, and are known to cause pandemics in humans. Influenza B viruses primarily infect humans and circulate seasonally, causing epidemics. Influenza C viruses cause mild respiratory illness and are not a significant public health concern. Influenza D viruses mainly affect cattle and are not known to infect humans.

The surface of the influenzavirus is covered with two key glycoproteins: hemagglutinin (HA) and neuraminidase (NA). HA plays a role in the virus's entry into host cells, while NA is involved in the release of newly formed virus particles from infected cells. The constant genetic variation of these surface proteins, through processes like antigenic drift and antigenic shift, is a hallmark of influenza viruses and necessitates the annual reformulation of influenza vaccines. Influenza viruses are transmitted through respiratory droplets expelled when infected individuals cough, sneeze, or talk.