YELLOW FEVER 451 



YELLOW FEVER. 



Yellow fever is an infectious disease which is endemic in the 

 West Indies, in Brazil, in Sierra Leone and the adjacent parts 

 of West Africa, though it is probable that it was from the 

 first-named region that the others were originally infected. 

 From time to time serious outbreaks occur, during which 

 neighbouring countries also suffer, and the disease may be 

 carried to other parts of the world. In this way epidemics 

 have occurred in the United States, in Spain, and even in 

 England, infection usually being carried by cases occurring 

 among the crews of ships. In the parts where it is endemic, 

 though usually a few cases may occur from time to time, there 

 is some evidence that occasionally the disease may remain in 

 abeyance for many years and then originate de novo. There is, 

 therefore, reason to suspect that the infective agent can exist 

 for considerable periods outside the human body. It is possible, 

 however, that continuity may be maintained by the occurrence 

 of a mild type of the disease which may be grouped with the 

 " bilious fevers " prevalent in yellow-fever regions. This would 

 explain the degree of immunity which is shown during a serious 

 epidemic by the older immigrants. 



Great variations are observed in the clinical types under 

 which the disease presents itself. Usually after from two to 

 six days' incubation a sudden onset in the form of a rigor 

 occurs. The temperature rises to 104- 105 F. The person is 

 livid, with outstanding bloodshot eyes. There are present great 

 prostration, pain in the back, and vomiting, at first of mucus, 

 later of bile. -The urine is diminished and contains albumin. 

 About the fifth day an apparent improvement takes place, and 

 this may lead on to recovery. Frequently, however, the remission, 

 which may last from a few hours to two days, is followed 

 by an aggravation of all the symptoms. The temperature rises, 

 jaundice is observed, hemorrhages occur from all the mucous 

 surfaces, causing, in the case of the stomach, the " black vomit " 

 one of the clinical signs of the disease in its worst form. 

 Anuria, coma, and cardiac collapse usher in a fatal issue. The 

 mortality varies in different epidemics from about 35 to 99 

 per cent of those attacked. Both white and black races are 

 susceptible, but those who have resided long in a country are 

 less susceptible than new immigrants. An attack of the disease 

 usually confers complete immunity against subsequent infection. 



Post mortem the stomach is found in a state of acute gastritis, 

 and contains much altered blood derived from hemorrhages 



