APPENDIX F. 



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 take place, during which 

 neighbouring countries also suffer, and the disease may be 

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

 have arisen in the United States and elsewhere, 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, there- 

 fore, 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 persistence 

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

 "bilious fevers" prevalent in yellow fever regions, and some 

 writers even speak of "carriers" of the virus. This would 

 explain the degree of immunity which is shown during a serious 

 epidemic by the older inhabitants. 



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 clay 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 

 on aggravation of all the symptoms. :■ The temperature rises, 

 ■ 87? 



