Flunssavirukset

Flunssavirukset, also known as influenza viruses, are RNA viruses belonging to the Orthomyxoviridae family. These viruses are responsible for causing influenza, commonly known as the flu, a contagious respiratory illness that affects millions of people worldwide each year. There are four main types of influenza viruses: A, B, C, and D. Influenza A and B viruses are the most common causes of seasonal epidemics in humans. Influenza A viruses are further categorized into subtypes based on two surface proteins: hemagglutinin (H) and neuraminidase (N). Common human subtypes include H1N1 and H3N2. Influenza C viruses typically cause mild respiratory illness, and influenza D viruses primarily affect cattle.

Transmission of influenza viruses occurs through respiratory droplets expelled when an infected person coughs, sneezes, or talks. These droplets can be inhaled by nearby individuals or land on surfaces, where they can remain infectious for a period. People can become infected by touching contaminated surfaces and then touching their eyes, nose, or mouth. Symptoms of influenza often include fever, cough, sore throat, muscle aches, headache, and fatigue. While most healthy individuals recover within a week or two, influenza can lead to serious complications, particularly in young children, older adults, pregnant women, and individuals with chronic health conditions.

Influenza viruses are known for their ability to change over time through a process called antigenic drift, which leads to minor changes in their surface proteins. This is why new influenza vaccines are developed annually to target the strains predicted to be circulating in the upcoming season. More significant changes can occur through antigenic shift, which involves the reassortment of genetic material between different influenza virus strains. This can lead to the emergence of novel viruses to which most people have little or no immunity, potentially causing pandemics.