7. Viral infections Flashcards
1
Q
What are the 3 possible outcomes following host infection by a virus?
A
acute infection, latent infection or chronic infection
2
Q
What is acute viral infection?
A
- virus undergoes multiple rounds of replication causing death of host cell (used as factory for virus production
- shorter timeframe
3
Q
What is latent viral infection?
A
- caused by DNA viruses or retroviruses
- persistence of viral DNA either as extrachromosomal element (herpesviruses) or as integrated sequence within host genome (retroviruses) - during cell growth, viral genome is replicated with chromosomes of host cell.
- does not result in production of progeny virus until reactivation
4
Q
What is the consequence of latent infection by some retroviruses?
A
cell transformation, leading to cancer
5
Q
What is chronic viral infection?
A
- usually RNA viruses
- virus particles continue to be shed after period of acute illness
- amount of virus produced often less than in acute infection and viruses are often mutated from original
- associated with defective host immune responses that are insufficient to clear infection.
- some chronic infections do not result in overt disease but can produce disease after prolonged interval
6
Q
Give examples of the 3 types of viral infection.
A
i) acute: poliovirus or influenza virus
ii) latent: infectious mononucleosis caused by Epstein-Barr virus
iii) chronic: chronic hepatitis (and even liver cancer) caused by hepatitis C virus
