Super Flu:

Antigenic shift in influenza

Imagine that the year is 1919. You have just survived one of the greatest infectious disease disasters of the 20th century. Twenty million people world-wide (500,000 in the United States) have died from a brutal disease that causes their lungs to fill with fluid and their bloodstream to be filled with deadly toxins. A large number of these people were young adults with no previous health problems.

The disease responsible is influenza : the common flu.

An outbreak such as the one in 1918 could easily occur again if the influenza virus were to undergo a process known as "antigenic shift".

The information below and on following pages describes antigenic shift in influenza and its consequences for public health.

Anatomy of the virus:
Influenza viruses are composed of an icosahedral (20-sided) protein capsid surrounded by a lipid envelope. Imbedded in the envelope are spikes of two proteins; hemagglutinin (H) and neuraminidase (N). H and N are coded for by two separate pieces of viral RNA. Influenza has 8 pieces of RNA total.

Antigenic shift:
The animation to the left shows antigenic shift occuring due to reassortment of RNA segments from two different viral strains infecting the same cell.

View the frames singly with explanatory text.