Orthomyxoviridae facts for kids

The Orthomyxoviridae are a family of RNA viruses. The name comes from Greek words meaning "straight" and "mucus." This family includes five main groups, called genera: Influenzavirus A, Influenzavirus B, Influenzavirus C, Thogotovirus, and Isavirus.

The first three groups (Influenzavirus A, B, and C) contain viruses that cause influenza, also known as the flu. These flu viruses can infect many different vertebrates, including humans, birds (like in avian influenza), and other mammals.

Other viruses in this family infect different animals:

• Isaviruses infect salmon.
• Thogotoviruses can infect both vertebrates and invertebrates, such as mosquitoes and sea lice.

The three main types of Influenzavirus are different because of the structure of their proteins. They infect vertebrates in these ways:

• Influenzavirus A causes all flu pandemics and can infect humans, other mammals, and birds.
• Influenzavirus B mainly infects humans and seals.
• Influenzavirus C infects humans and pigs.

Types of Influenza Viruses

There are three main types of influenza virus: Influenzavirus A, Influenzavirus B, and Influenzavirus C. Each type includes only one species. Influenza A and C can infect many different animals, but influenza B mostly infects humans.

Influenza A

Influenza A viruses are further divided based on two special proteins found on their surface: hemagglutinin (HA or H) and neuraminidase (NA or N). Scientists have found 16 different H types and 9 different N types of influenza A virus.

Because there are so many variations, each specific influenza strain is named using a standard system. This name tells you the virus type, where it was first found, a number showing its order of discovery, the year it was found, and its H and N types.

For example:

• A/Moscow/10/99 (H3N2)
• B/Hong Kong/330/2001

Type A viruses are the most powerful human pathogens among the three influenza types. They cause the most severe illness. The types that have been found in humans and caused the most deaths are:

• H1N1 caused the "Spanish Flu".
• H2N2 caused the "Asian Flu".
• H3N2 caused the "Hong Kong Flu".
• H5N1 was a big concern for a pandemic in 2006-2007.
• H7N7 can spread from animals to humans in unusual ways.
• H1N2 is common in humans and pigs.
• Other types include H9N2, H7N2, H7N3, and H10N7.

Influenza B

Influenza B virus mostly infects humans. It is less common than influenza A. The only other animal known to get influenza B is the seal. This type of influenza changes (mutates) slower than type A. Because of this, it is not as genetically diverse, and there is only one influenza B type.

Since it doesn't change as much, people usually get some protection against influenza B when they are young. However, influenza B still changes enough that you cannot have lasting immunity for your whole life. This slower change, combined with its limited host range (meaning it doesn't easily jump between different animal species), means that influenza B does not cause pandemics.

Influenza C

The influenza C virus infects humans and pigs. It can cause serious illness and local epidemics (outbreaks in a specific area). However, influenza C is less common than the other types. It usually causes mild sickness, especially in children.

Images for kids

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  Structure of the influenza virion. The hemagglutinin (HA) and neuraminidase (NA) proteins are shown on the surface. The viral RNAs are shown as red coils inside.

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  Influenza A virus structure

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  Influenzavirus genomes. Segments translate to polymerase (PB1, PB2, and PA), hemagglutinin (HA), neuramindase (NA), nucleoprotein (NP), membrane protein (M), and non-structural protein (NS).

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  Transcription of mRNAs initiated by viral polymerase using cap snatching

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  Targets of anti-influenza agents that are licensed or under investigation

See also

In Spanish: Orthomyxoviridae para niños