Dengue Review by State

East and South Africa

South Africa (Natal)

00000000A big epidemic occurred in 1926 - 1927 in the town of Durban, where more than 40 000 cases were suspected. Haemorrhagic syndromes seem to have been frequent and probably also shock syndromes since Edington(2) mentioned "many serious cases of cardiac decompensation". The real nature of this epidemic was only recognized in 1956, when Kokernot et al(11) found DEN-1 antibodies in the blood of nine 26-year-olds. No other positive response for DEN-1 or DEN-2 viruses was found outside the Durban area and, considering the commercial relations of this harbour, it is most likely that the virus was introduced from South-East Asia.

00000000More recently, a case of DEN-1 was diagnosed in Durban by virus isolation from a patient just returned from India; several other cases were suspected in the same area(12).

Indian Ocean Islands

00000000During World War II or immediately after, epidemics occurred in the Comoro Islands(3,4) as well as in Diego-Suarez in Madagascar(5). None of these epidemics was serologically investigated and their dengue nature has remained doubtful.

00000000In 1976 - 1978, the Seychelles Islands experienced an extensive epidemic which affected at least 60 per cent of the population(13). This epidemic started in December 1976, at the beginning of the rainy season, reached its peak in February 1977 and lasted until September 1977; sporadic cases were observed in 1978 and there was a small resurgent epidemic between September 1978 and January 1979(14). The rainfall is 2000 - 3000 mm per year and occurs from December to March. The epidemic spread through nearly all of the inhabited islands of the archipelago. Twenty-three DEN-2 virus isolates were obtained from the 36 tested sera and a retrospective serological survey in the town of Mahe showed only two negative responses for DEN antigen out of 231 tested sera(13). Most of the sera were positive for the four antigenic types. Clinically, most of the cases were typical dengue, the rash being less frequent than usual. No haemorrhagic syndrome or shock syndrome was noticed, but there were deaths caused by encephalitis and meningitis of "probably viral" origin. Cases occurred in indigenous people as well as in expatriates. The most likely vector was Aedes albopictus, which is very abundant during the rainy season; twenty-three tested pools of this species yielded five isolates; isolates were also made from two of eight Culex quinquifasciatus pools and from one of the two Styloconops spinosifrons (Ceratopogtonidae) pools, but the virus might have resulted from recently ingested blood.

00000000At the same time (1978) an epidemic was observed in La Reunion Island, and the nature of the epidemic was suspected after a single DEN-2 virus isolate was made at the Pasteur Institute of Madagascar from the blood of a patient who had just arrived from La Reunion. The number of cases was estimated at about 160 000, that is to say 30 to 35 per cent of the total population, and no DHF or DSS was recorded(15).