Mozambique

00000000The Health Ministry of Mozambique recorded an epidemic in Pemba (province of Cabo Delgado), which begun in October 1984 at the beginning of the rainy season, and lasted until March 1985(20). At least two deaths were attributed to this disease initially thought to be malaria, and DEN-3 virus was isolated and identified in the sera of four patients. A decrease in blood platelets was frequently noted. This is the first record of DEN-3 virus in Africa.

West Africa

Nigeria

00000000Nigeria was the first African country to carry out exhaustive studies on dengue. Between the first virus isolate, in 1964, and 1975(21-24), dengue viruses were recovered from 68 patients (38 DEN-1 and 30 DEN-2). Most of the cases were children less than four years old and most of the samples examined were from children; cases in adults were few and most of them were hospital or laboratory personnel(25). Diseases were mild ones, generally milder in young patients, and no DHF or DSS was noticed. Three strains of DEN virus were obtained from children with febrile convulsions(26). A single case with low haemorrhagic tendency was diagnosed in as American physician.

00000000Epidemiologically, all cases diagnosed were from the rain forest area, mainly from Ibadan because surveillance was higher in this city. The virus was isolated all the year round, except in the dry months of February and March, with the peak occurring in August, which corresponded to a short dry season between the two rainy seasons. A single isolate of DEN-2 virus was obtained from Adeds aegypti caught in Ibadan in August 1969(21).

00000000The first suspicions of a sylvatic cycle of dengue were aroused after serological surveys were carried out to investigate yellow fever on the Benue Plateau(27) and in the Nupeko Forest(28). Neutralizing antibodies for DEN-2 antigen were commonly found in the sera of village inhabitants a well as in some monkey sera from an area where A. aeghpti is not prevalent(29). Further investigations were carried out in the southern part of Nigeria by means of a serological survey in monkeys and humans(30), and the results showed that DEN viruses were prevalent in the four ecological zones studied. In the rain forest area the antibody prevalence was about equal in urban and rural areas (43 per cent and 41 per cent respectively). The highest prevalence was in derived savannah zones, and it was higher in urban than in rural areas (67 per cent and 33 per cent respectively). In the southern Guinea savannah zone, the rate was also higher in urban areas but lower than in derived savannah zones (urban areas 45 per cent and rural areas 32 per cent). On the plateau, dengue antibodies were found only in the urban community (30 per cent). The hypothesis of a sylvatic cycle of DEN viruses was reinforced by the isolation of a DEN-2 virus strain from wild caught unidentified Stegomyia, probably Aedes luteocephalus, on the Jos Plateau in November 1969, and by the isolation of two strains of DEN-1 virus from Aedes africanus in the Mamu River Forest (Eastern Nigeria) in 1977(31).