224 REPORT OF THE HARVARD AFRICAN EXPEDITION 
in Liberia during the long intervals between fatal cases, in children and adults 
who have a relative immunity and who undergo very mild attacks of the infec- 
tion and recover. Certainly Monrovia has no high death rate from any single 
disease, and there has been no large epidemic of any infectious disease for a 
number of years. 
An outbreak of yellow fever also occurred on the west coast of Africa in 
Senegal and in Accra and Lagos, during the year 1927. Cases also occurred in 
Dahomey and in the Ivory Coast. Lasnet ! reported six cases among the Euro- 
peans, three in Dahomey of which one was fatal, and three in the Ivory Coast, all 
fatal. Lasnet ? and Cazanove ® have described the epidemic of yellow fever in 
Senegal in 1927. The total number of cases from May to the thirty-first of 
December, for the entire colony, was 190, of which 135 died, a mortality of 70.89 
per cent. Eighty-two of the cases, with fifty-eight deaths occurred in Dakar. 
Selwyn-Clarke 4 reports that in Accra the epidemic in the colony in 1927 affected 
the African population rather more than the European, as there were eighty- 
eight cases with twenty-five deaths in the former and fourteen cases with ten 
deaths in the latter. In addition there were five cases of Syrians with five deaths. 
Mouchet ° has reported upon the first outbreak of the disease recorded from the 
Congo which occurred in Matadi and Boma in December, 1927 and January, 
1928. At Boma there were only three cases, two imported and one local and no 
natives were affected. At Matadi there were nineteen cases among Europeans 
of which eight recovered and eleven died. Twenty natives became infected, of 
whom five recovered and fifteen died. Sicé and Vaucel ® have found that Aédes 
aegypti (Stegomyia fasciata) is abundant at Brazzaville, one hundred and fifty- 
five miles further up the Congo than Matadi. Apparently this mosquito may be 
found when looked for in almost any part of the Congo. It has been shown to 
exist at Stanleyville by Dr. Mouchet, at Albertville on Lake Tanganyika (Dr. 
Schwetz), and at Elisabethville in Katanga (Dr. Schwetz). 
The west coast of Africa has long played an important part in the history of 
yellow fever. Reference has already been made to the suggestion that the mos- 
quito, Aédes aegypti, which commonly transmits the infection was originally 
imported into America from the West African coast. As yellow fever still occurs 
from time to time along this coast, it is of some interest to refer here to the 
recent advances made in our knowledge of this disease. 
After the isolation of Leptospira icterohaemorrhagiae by Inado and Ito in 
hemorrhagic jaundice, and of Leptospira icteroides by Noguchi from cases of 
yellow fever, we had frequent opportunity to compare the micro-organisms. 
For several years in our laboratories we were unable to distinguish any differ- 
ences, either in morphology or pathogenic action in animals, between Leptospira 
icteroides and Leptospira icterohaemorrhagiae, and we asked the question, — Is 
1 Lasnet: Bull. Office Intern. d’Hyg. Publique (1929), X XI, 49. 
2 Lasnet: Ibid., p. 54. 
3 Cazanove: Bull. Soc. Path. Exot. (1929), XXII, 260. 
4 Selwyn-Clarke: Gold Coast Report of Med. and San. Dept. for the year April 1927 to March 
1928, XX VII, 121; also Brit. Med. Jour. (1980), p. 298. 
5 Mouchet: Ann. Soc. Belge de Méd. Trop. (1928), VIII, 219. 
6 Sicé and Vaucel: Bull. Soc. Path. Exot. (1928), X-XI, 768. 
