WHILE NEW and exotic viral diseases have occupied much media attention in recent years, among scientists and public health officials a major concern has been to try to deal with one of the oldest viral infections known—influenza.
Influenza, with its ability to cause repeated epidemics of respiratory illness, can also be viewed as a new, emerging disease. Periodically the virus rises, phoenixlike, from the genetically reassorted residues of its antecedents to sweep through a susceptible human population, leaving death and destruction in its wake.
For many years, these shifts in the antigenic constitution of influenza have been monitored with the goal of developing effective vaccines against the new viral strains that emerge. In most years the antigenic changes are minor, but every now and again the virus undergoes a major change and causes a worldwide epidemic—a pandemic—of sudden and widespread illness. Such an event occurred in 1918-1919 and caused an