What type of virus is the flu

Influenza A viruses are classified by subtypes based on the properties of their hemagglutinin H or HA and neuraminidase N or NA surface proteins. There are 18 different HA subtypes and 11 different NA subtypes. Subtypes are named by combining the H and N numbers — e. Click on the image to enlarge the picture. There are four types of influenza viruses: A, B, C and D.

Human influenza A and B viruses cause seasonal epidemics of disease known as flu season almost every winter in the United States. Influenza A viruses are the only influenza viruses known to cause flu pandemics, i.

A pandemic can occur when a new and different influenza A virus emerges that both infects people and has the ability to spread efficiently among people.

Influenza C virus infections generally cause mild illness and are not thought to cause human epidemics. Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus: hemagglutinin H and neuraminidase N.

There are 18 different hemagglutinin subtypes and 11 different neuraminidase subtypes H1 through H18 and N1 through N11, respectively. Reassortment can occur when two influenza viruses infect a host at the same time and swap genetic information.

This graphic shows the two types of influenza viruses A and B that cause most human illness and that are responsible for flu seasons each year. Both influenza A and B viruses can be further classified into clades and sub-clades which are sometimes called groups and sub-groups.

Note that this graphic is an example, and currently circulating influenza clades and subclades may differ from those presented here.

Figure 1 — This is a picture of a phylogenetic tree. Each sequence from a specific influenza virus has its own branch on the tree. The degree of genetic difference between viruses is represented by the length of the horizontal lines branches in the phylogenetic tree. The further apart viruses are on the horizontal axis of a phylogenetic tree, the more genetically different the viruses are to one another.

Viruses gain their infamy through a combination of large infection rates and death, even when their power has been relatively subdued. Rabies, measles and chickenpox are still notorious, even though vaccines and medications have drastically reduced their deadliness. There are three different virus types that are made distinct by their shape.

The cylindrical helical virus type is associated with the tobacco mosaic virus. Envelope viruses, such as influenza and HIV come covered in a protective lipid envelope. Most animal viruses are classified as icosahedral and are nearly spherical in shape. The viruses within these categories share similar characteristics. Viruses are also the most abundant biological form of life on the planet. The first thing a virion does is enter a cell and becomes a virus. Next, it reproduces, creating viral protein and genetic material instead of the usual cellular products.

A virus can then spread through a wide variety of means, such as touching, coughing and sneezing. The body fights viruses by breaking down the viral genetic material via RNA interference. The immune system then produces antibodies that bind to viruses to make them noninfectious. Lastly, T cells are sent to destroy the virus. Antiviral drugs can treat viruses by inhibiting viral development and slowing down disease progression. These drugs help fight the flue, chickenpox and forms of hepatitis.

Vaccines create a herd immunity that helps prevent an outbreak. There are five different types of viruses: Conjugate vaccines, inactivated vaccines, live, attenuated vaccines, subunit vaccines and toxoid vaccines. There are several ways people can slow the spread of a virus in lieu of drugs or vaccination.

H7 virus infection in humans is uncommon. The most frequently identified H7 viruses associated with human infection are Asian lineage avian influenza A H7N9 viruses, which were first detected in China in While human infections are rare, these have commonly resulted in severe respiratory illness and death. Rare, sporadic H9N2 virus infections in people have been reported to generally cause mild upper respiratory tract illness; one infection has results in death.

Skip directly to site content Skip directly to page options Skip directly to A-Z link. Influenza Flu. Section Navigation.

Facebook Twitter LinkedIn Syndicate. Influenza Type A Viruses. Minus Related Pages. On This Page. Get Email Updates. To receive email updates about this page, enter your email address: Email Address.