920 DISEASES CAUSED BY FILTRABLE VIRUS 



Great Britain and Algeria in late 1917, and early 1918, and reached 

 North America during the latter half of 1918 and in early 1919. The 

 disease spread rapidly throughout the United States, and Smith says 

 that by May, 1919, cases had been reported from twenty of the states. 

 The largest number were reported from Illinois, New York, Louisiana, 

 and Tennessee, a fact which shows the apparent independence of the 

 disease of climatic conditions. The disease spread through the United 

 States from east to west. Smith summarizes the epidemiological 

 features as follows: In almost all outbreaks the appearance of epi- 

 demic encephalitis has been preceded by influenza. Evidence of direct 

 communicability is lacking, since in analyzing approximately 900 

 people exposed in the immediate families of cases, no secondary cases 

 occurred. The age distribution is entirely different from poliomye- 

 litis, so much so that Smith believes that this alone would distinguish 

 the two diseases. In poliomyelitis over 59 per cent, of the cases occur 

 before the fourth year, and 68 per cent of the cases occur below the 

 age of 5, whereas in epidemic encephalitis 58 per cent, of the cases 

 occurred in individuals 20 years of age and over. As to sex, 60 per 

 cent of the cases of encephalitis occurred in males. Seasonally the 

 apex of the epidemic curve in the United States was reached in March. 



The relationship of the disease to influenza is vague, but something 

 to be very seriously considered in view of the recent researches of 

 Olitsky with influenza and of Strauss and Loewe on filtrable virus in 

 encephalitis. 



The onset is usually gradual, with headache, lassitude and grad- 

 ually increasing fever. Occasionally there are vomiting, vertigo and 

 muscular pains. Disturbances of vision may appear early. Following 

 this there may be an acute stage during which the fever rises, vomit- 

 ing may intensify, there may be disturbances of the cranial nerves 

 and great general weakness which gradually lapses into coma. Occa- 

 sionally a case may get well in two or three weeks following this, again 

 the coma may persist for a long time. Paralysis of muscular groups 

 and facial paralysis, ptosis, disturbances of pupil reflexes and other 

 muscular reflexes occur. 



The spinal fluid shows an increased number of cells in a certain 

 percentages of cases. The leucocytes may be slightly increased, but 

 are usually not very high. The mortality in Smith 's study was 29 per 

 cent. 



The etiology of the disease has been very carefully worked upon 

 since the last appearance of the disease. A number of bacteria have 



