[Dengue epidemic in New Caledonia (1989). Environmental factors and prevention]

An extensive dengue epidemic was reported in New Caledonia en 1989. Environmental factors (temperature and rainfalls) directly controlled the mosquitos population at the end of 1988. The introduction of a new dengue virus, transmitted by Aedes aegypti, was responsible for an epidemic that occurred in January-April 1989 and lasted until July 1989. The 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 involved mainly the adult population in 84% of cases and 6-8% of patients was admitted in hospital with thrombopenia, leucopenia, minor haemorrhages in 2/3 of cases and 12 patients died with severe hemorrhagic disease or shock syndrome; initial serological results from suspected cases were positive against dengue by haemaglutination inhibition. Two dengue viruses were involved (dengue 1 and dengue 3) but dengue 3 was by far the most common. Ultra-low volume aerosols of diluted insecticide (decamethrine K'Othrine, Roussel) from road vehicles and aircraft was used from February to May to kill the adult mosquitoes (adulticiding). The efficacy dependent on the interaction of the insecticide and the flying mosquitoes is relative and debated but played probably a major role on the transmission, though the reduction of breeding sites was primarily uncovered. Since the epidemic, only sporadic cases were observed in 1991 and 1992.