CHAPTER XLIV 



YELLOW FEVER AND THE LEPTOSPIRA ICTEROIDES, WEIL'S DIS- 

 EASE (INFECTIOUS JAUNDICE) AND LEPTROSPIRA ICTERO- 

 HEMORRILEGLZE 



YELLOW fever is an acute infectious disease which prevails en- 

 demically in the tropical countries of the Western Hemisphere, but 

 occurs also along the western coast of Africa and has exceptionally 

 appeared, in epidemic invasons, in the north temperate United 

 States and Europe. Guiteras, as quoted by Osier, classifies the 

 distribution of the disease into three areas of infection. 



1. The area in which the disease is never absent, including 

 tropical South American ports and Havana. 



2. The area of periodic epidemics, including sea-ports of the 

 tropical Atlantic in America and Africa. 



3. The area of accidental epidemics, extending from parallel 45 

 north latitude to 35 south latitude. In the United States severe 

 epidemics have frequently occurred in Louisiana, Mississippi, and 

 Alabama, and occasional but severe epidemics have occurred in 

 Philadelphia and Baltimore. 



The disease occurs spontaneously only in man, and experimental 

 inoculation of lower animals has been successful only in the chim- 

 panzee in a single case reported by Thomas. 1 



In man afflicted with the malady the clinical picture is one of 

 a rapidly developing fever with severe gastrointestinal symptoms, 

 vomiting of blood, albuminuria, and often active delirium. The mor- 

 tality is usually high, often reaching eighty per cent or more in 

 the severe epidemics. 



Mode of Transmission. Until comparatively recent years the 

 mode of transmission of yellow fever was not understood and many 

 erroneous theories were prevalent. It was supposed that yellow 

 fever was contagious, and transmitted from person to person by 

 direct or indirect contact with those afflicted or by fomites. The 

 first to make the definite assertion that yellow fever was transmitted 



1 Thomas, Brit. Med. Jour., 1, 1907. 



874 



