Orthomyxoviridae

The Orthomyxoviridae (orthos, Greek for "straight"; myxa, Greek for "mucus") are a family of RNA viruses that includes five genera: Influenzavirus A, Influenzavirus B, Influenzavirus C, Isavirus and Thogotovirus. A sixth has recently been described. The first three genera contain viruses that cause influenza in vertebrates, including birds (see also avian influenza), humans, and other mammals. Isaviruses infect salmon; thogotoviruses infect vertebrates and invertebrates, such as mosquitoes and sea lice.

The three genera of Influenzavirus, which are identified by antigenic differences in their nucleoprotein and matrix protein, infect vertebrates as follows:

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