APRIL 1953

INFLUENZA VS. IMMUNITY--"The serological character of the A virus has changed seven or eight times since 1933, and each change in character has within a year been evident all over the earth. Soon after influenza A2 was found in the U.S., it appeared in Australia and England as well. After it had taken hold, no A1 strains were found anywhere. And so for each successive change. It is a parasite whose only natural host is man. To survive, it must pass continually from one human being to another--it is inhaled and lodges in the respiratory tract. But it soon finds itself in the position epidemiologists call 'exhaustion of susceptible hosts.' In other words, almost the entire population becomes immune. This highly transmissible virus meets the situation by a transformation of character--a mutation that enables it to overcome its host's immunity. --Sir Macfarlane Burnet" [Editors' note: Burnet was a co-winner of the 1960 Nobel Prize for Physiology or Medicine "for discovery of acquired immunological tolerance."]

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