influensastammene

Influensastammene, also known as influenza viruses, are a type of virus that cause influenza, commonly known as the flu. There are four types of influensastammene, classified by their surface proteins: A, B, C, and D. Types A and B are the most common and cause seasonal influenza epidemics. Type C is less common and generally causes mild illness. Type D primarily affects cattle and is not known to cause disease in humans.

Influenza viruses are RNA viruses that belong to the Orthomyxoviridae family. They are enveloped viruses with a segmented, single-stranded RNA genome. The virus is approximately 80-120 nanometers in diameter and has a helical nucleocapsid.

Influenza viruses are transmitted through respiratory droplets produced when an infected person coughs or sneezes. They can also be transmitted through contact with contaminated surfaces. The virus can survive on surfaces for several hours to days, depending on the type of surface.

Influenza viruses are classified into subtypes based on the surface proteins hemagglutinin (H) and neuraminidase (N). There are 18 different H subtypes and 11 different N subtypes. The most common subtypes in humans are H1N1 and H3N2.

Influenza viruses are responsible for millions of illnesses and hundreds of thousands of deaths worldwide each year. The virus is particularly dangerous for high-risk groups, including young children, the elderly, and individuals with compromised immune systems.

Influenza viruses are subject to antigenic drift and shift. Antigenic drift is a gradual, continuous change in the virus's surface proteins, which can lead to the emergence of new strains. Antigenic shift is a sudden, major change in the virus's surface proteins, which can lead to a pandemic. The 2009 swine flu pandemic was caused by an antigenic shift in an H1N1 virus.

Influenza viruses are treated with antiviral drugs, such as oseltamivir and zanamivir, which can shorten the duration and severity of symptoms. Vaccination is the primary method of prevention, with new vaccines developed each year to match the circulating strains.