492 THE CONTROL OF MALARIA AND YELLOW FEVER 



Later Investigations. Hideyo Noguchi of the Rockefeller Insti- 

 tute isolated a microorganism, called a spirochaete, from yellow 

 fever victims in South America, which has been, until recently, a 

 focus for yellow fever. It is more like a protozoan than a bac- 

 terium. He made a vaccine from this organism, which is admin- 

 istered early in the disease and is very effective. The disease 

 has been practically exterminated in the Western Hemisphere, 

 due to his efforts. But experimental workers in Africa were 

 unable to isolate the spirochaete from the blood of victims of 

 yellow fever in that country. They were unable to inoculate 

 monkeys and guinea pigs with the disease as Noguchi had done. 

 Apparently, the germ causing yellow fever in Africa was differ- 

 ent from that causing the disease in South America. Noguchi 

 went to Africa to investigate the disease and he succeeded in 

 inoculating one species of monkey with the disease. Unfortu- 

 nately Noguchi became infected with yellow fever in Lagos, 

 Nigeria, and died in the spring of 1928. After he contracted 

 the fever, he insisted that samples of his own blood be inoculated 

 into monkeys. His associates carried on his experiments with 

 the cultures which he had started. It has not yet been decided 

 whether there are one or two types of yellow fever. From data 

 left by Noguchi, the Rockefeller Institute for Medical Research 

 is inclined to believe that there are two distinct forms of the 

 disease. Scientists are most anxious to clear up the infection 

 in western Africa before the transcontinental railroad is opened. 

 If the disease spreads to the East Coast, it may pass over into 

 India and southern China, which are full of the Aedes mosquito. 



Cause. A spiral protozoan, spirochaete, was discovered in 

 1918 by Noguchi and designated by him as the cause of yellow 

 fever. Experiments are being performed, at the present time, to 

 determine whether or not the spirochaete is really the specific or- 

 ganism causing yellow fever. The vaccine prepared by Noguchi 

 has not yet been accepted as a definite preventive. 



