Influenza Virus Research Reagents

Influenza (the flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness. Serious outcomes of flu infection can result in hospitalization or death. There are four species of influenza viruses:

• A (IAV; genus, Alphainfluenzavirus)
• B (IBV; Betainfluenzavirus)
• C (ICV; Gammainfluenzavirus)
• D (IDV; Deltainfluenzavirus)

IAV and IBV cause seasonal epidemics of disease (known as the flu season) Influenza A viruses are the only influenza viruses known to cause flu pandemics and are responsible for most cases of severe illness of “the flu”.

Influenza A viruses are divided into subtypes based on the two surface proteins of the virus: hemagglutinin (H) and neuraminidase (N). One way influenza viruses change is called “antigenic drift.”, which results from mutations in the genes of the two surface proteins. The small changes that occur from antigenic drift usually produce viruses that are closely related to one another and therefore have similar antigenic properties.

Conversely “antigenic shift” causes an abrupt, major change in influenza A virus, resulting in new H and/or new H and N proteins, which can infect humans. One way shift can happen is when an influenza virus from an animal population gains the ability to infect humans. Such animal-origin viruses can contain an H or H/N combination that is so different from the same subtype in humans that most people do not have immunity to the new virus. Such a “shift” occurred in the spring of 2009 when an H1N1 virus with genes from North American Swine, Eurasian Swine, humans, and birds emerged to infect people and quickly spread, causing a pandemic. When shift happens, most people have little or no immunity against the new virus.