A DENGUE EPIDEMIC IN NEW-CALEDONIA (1989) - ENVIRONMENTAL-FACTORS ANDPREVENTION

An extensive dengue epidemic was reported in New Caledonia en 1989. En vironmental factors (temperature and rainfalls) directly controlled th e mosquitos population at the end of 1988. The introduction of a new d engue virus, transmitted by Aedes aegypti, was responsible for an epid emic that occurred in January-April 1989 and lasted until July 1989. T he estimated number of cases was 25,000 and the attack rate was close to 120 per thousand inhabitants for a six month-period. The epidemic i nvolved mainly the adult population in 84% of cases and 6-8% of patien ts was admitted in hospital with thrombopenia, leucopenia, minor haemo rrhages in 2/3 of cases and 12 patients died with severe hemorrhagic d isease or shock syndrom; initial serological results from suspected ca ses were positive against dengue by haemaglutination inhibition. Two d engue viruses were involved (dengue 1 and dengue 3) but dengue 3 was b y far the most common. Ultra-low volume aerosols of diluted insecticid e (decamethrine K'Othrine, Roussel) from road vehicles and aircraft wa s used from February to May to kill the adult mosquitoes (adulticiding ). The efficacy dependant on the interaction of the insecticide and th e flying mosquitoes is relative and debated but played probably a majo r role on the transmission, though the reduction of breeding sites was primarily uncovered. Since the epidemic, only sporadic cases were obs erved in 1991 and 1992.