Antigenic shift

Definition

Antigenic shift is a process in which two or more different strains of a virus, or viruses from different species, combine to form a new subtype with a mixture of surface antigens. This can lead to sudden and major changes in the virus's antigenic properties.

5 Must Know Facts For Your Next Test

1. Antigenic shift is most commonly associated with influenza A viruses.
2. It can result in pandemics due to the lack of pre-existing immunity in the human population.
3. The process typically involves the reassortment of RNA segments when two different strains infect the same host cell.
4. Antigenic shift leads to significant changes that are not achievable by antigenic drift, which involves smaller, gradual mutations.
5. It is responsible for major global outbreaks like the Spanish flu (H1N1) in 1918 and the H1N1 pandemic in 2009.

Review Questions

• What types of viruses are primarily involved in antigenic shift?
• How does antigenic shift differ from antigenic drift?
• Why can antigenic shift lead to pandemics?

Related terms

antigenic drift: A gradual change in virus antigens due to point mutations.

reassortment: The process where segments of RNA from different viral strains mix during co-infection of a host cell.

pandemic: A worldwide outbreak of a disease affecting large numbers of people.