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December 29, 1923


JAMA. 1923;81(26):2186-2187. doi:10.1001/jama.1923.02650260028012

Discovery in the etiology of infectious disease has been limited largely to bacteria that are microscopically visible. Many years ago, however, certain disease-producing agents were recognized that were invisible and so small that they would pass fine earthenware filters. These were termed ultramicroscopic. Now, it seems, some of the organisms heretofore listed as ultramicroscopic can be made visible and so the whole group has come to be classed as the filtrable viruses.

In a recent review, Simon 1 refers to a list of forty-one diseases affecting man and various animals published by Lipschütz2 in 1913, in which the filtrable nature of the causative agent had been established with some certainty. Among these were the important epidemic diseases smallpox, yellow fever, measles, scarlet fever, poliomyelitis, dengue and trachoma, to which might be added now influenza, herpes and possibly epidemic encephalitis.

It is a curious fact, says Twort,3 that no