P18 DISEASES CAUSED BY FILTRABLE VIRUS 



There is a great deal of evidence to show that poliomyelitis car- 

 riers exist. Experimental evidence of this carrier state has been ad- 

 vanced by Osgood and Lucas 16 who found the virus in monkeys five 

 months after convalescence. We ourselves have seen cases in which 

 it could be definitely proven that they had not been in contact with 

 a preceding case, two of them in country districts where the scantily 

 populated surrounding area could be searched without danger of 

 overlooking a case. It is also likely that at times of epidemic a 

 great many very mild attacks of poliomyelitis may occur, which are 

 mistaken for mild influenza or severe colds, and in connection with 

 the occurrence of a recent case seen by us there were a number 

 of indefinitely diagnosed cases of intestinal disturbance, with fever, 

 in the neighborhood. It is not impossible that such cases may be 

 true poliomyelitis of a mild type without paralysis but capable of 

 passing on the virus. Peabody, Dochez and Draper 17 have cited 

 similar cases. 



The virus probably gets into the new patient by direct and in- 

 direct contact, and can be carried from place to place, perhaps on the 

 feet of flies, a fact which would be indicated by some experiments 

 done by Flexner. 



In 1911 epidemiologists of the State Public Health Service of 

 Massachusetts established a parallelism between the distribution of 

 poliomyelitis cases and the occurrence of the biting stable fly, Stomoxys. 

 Subsequently, M. J. Rosenau published experiments in which he 

 obtained poliomyelitis infection by allowing infected Stomxys flies to 

 bite monkeys. These observations were confirmed by Anderson and 

 Frost, 18 but all subsequent attempts to repeat the experiments have 

 failed. The ordinary manner of infecting of the human being is 

 probably, then, through the nasopharynx. A great many cases begin 

 with intestinal disturbances which may last a few days before the 

 patient is ill enough to go to bed. It is more than likely, therefore, 

 that the virus may also enter the body by ingestion and that infection 

 of food may play a role. 



The disease is usually present to some extent in crowded centers 

 of the world, in the spring and summer months. The season of greatest 

 prevalence is May to November. Most cases are in children below five, 

 but adult cases do occur. 



14 Osgood and Lucas, Journal A. M. A., 57,' 1911, p. 495. 



17 Peabody, Draper and Dochez, Monog. Rock. Inst., No. 4, Jan., 1912. 



18 Anderson and Frost, Journ. A. M. A., 56, 1911, p. 663. 



