Possible dengue sequential infection: dengue spread in a neighbourhood during the 1996/97 dengue-2 epidemic in French Polynesia

A DEN-2 epidemic occurred in French Polynesia from August 1996 to April 199 7 after 7 years of DEN-3 circulation. The susceptible population constitute d all expatriates and Polynesians under 21. In August 1996, two successive DEN-2 cases occurred in Teroma, a Tahitian neighbourhood close to the inter national airport of Tahiti. A serological prospective study of persons < 21 years living in Teroma was conducted. The study population was bled in Sep tember 1996, October 1996 and June 1997. Analysis of dengue spread in Terom a confirmed that dengue transmission occurs primarily in the house, thus ve ctor control campaigns should incorporate focal insecticide spraying and sy stematic daily use of insecticide in houses. The evolution in time of the d isease demonstrated that among a susceptible population, prevalence and inc idence rates are related to the time of exposure, and consequently to age. Comparison of dengue incidence or dengue prevalence between populations the refore requires adjusted age rates. Most studies did not adjust for age, le ading to the conclusion that DHF is more frequent during secondary than dur ing primary dengue infection. Prospective studies taking into account the t ime of dengue exposure are necessary to confirm the sequential infection hy pothesis.