Question

5. What is antigenic shift? Explain the concept of antigenic shift with respect to influenza. How does antigenic shift affect the efficacy of the vaccine? 6. Which strains of influenza typically infect humans? 7. What are the typical symptoms associated with influenza?

Answer 1

5. Antigenic shift is the process through which two or more different virus strains or viruses combine to form a new subtype. This subtype have a mixture of the surface antigens of the original strains.

Antigenic shift is seen commonly in influenza virus. When two different influenza strains infect the same cell at same time, protein capsids and lipid envelopes are removed resulting in exposing their RNA, and transcription to mRNA. Thus new viruses are formed that combine their antigens. H3N2 and H5N1 exhibit antigen shift and form H5N2.

Antigenic shift results in formation of new subtype which is unaffected by the previous vaccine. This causes loss of immunity and vaccination mismatch.

6. Humans are infected by influenza A, influenza B and influenza C.

7. Influenza is an infectious disease and have symptoms resembling that of common cold. General symptoms of influenza are runny nose, headaches, chills and fever, red and watery eyes, body ache, sore throat, nasal congestion.