300 Microbes and You 



one always seems to be suffering from a common cold, or from 

 measles or mumps. 



EPIDEMIC DISEASE 



If endemic diseases increase in number very quickly, they be- 

 come EPIDEMIC {epi, upon; demos, people) in character. Child- 

 hood diseases have a way of appearing in epidemic waves among 

 school children. These diseases seem to disappear just as rapidly 

 as they came, even though there are still a number of children who 

 apparently were equally exposed yet resisted infection. Their im- 

 munity, in other words, protected them from particular attacks, 

 but subsequent epidemics, perhaps caused bv more virulent organ- 

 isms, may well affect those children who escaped the first wave of 

 a particular infection. 



PANDEMIC 



When epidemics "go wild," that is, spread over vast areas- 

 whole continents or over many continents— they are termed pan- 

 demics {pas, all; demos, people). The plague of the middle ages 

 and the influenza pandemic after World War I are classed in this 

 group. 



PRIMARY INFECTION 



A full-blown case of the common cold is probably caused not 

 by one but by a number of microorganisms. The primanj cause 

 appears to be a virus, but unless the infection progresses, a typical 

 common cold will not result. 



SECONDARY INFECTION 

 After the initial groundwork has been accomplished by the 

 primary invaders, secondary opportunists take over in the common 

 cold, and much of the misery of this affliction can be attributed 

 to these secondary infecting organisms. The use of antihistamines 

 might be considered to be an attempt to slip a wedge between the 

 primary and the secondary infections of a common cold. Some- 

 times it appears to work, while at other times, the disease takes its 

 usual course. The conclusion of an extensive study in England on 

 the causes and possible cures for the common cold are of interest. 



