FIELD EPIDEMIOLOGY OF AN OUTBREAK OF DENGUE FEVER IN CHARTERS TOWERS,QUEENSLAND - ARE INSECT SCREENS PROTECTIVE

Between March and July 1993 a dengue virus epidemic swept through Char ters Towers, a rural North Queensland mining community of 10 000. This clearly delineated outbreak provided an ideal opportunity to carry ou t one of the few field epidemiological studies of dengue in Australia. The epicurve was consistent with that of a point source outbreak, 18 weeks in duration and peaking at four weeks. A basic reproduction numb er for the dengue epidemic of 1.99 indicates a similar rate of spread to that found in dengue epidemics overseas. A female-to-male sex ratio of 1.7:1 was obtained for the 238 cases identified. An age- and sex-m atched retrospective case-control study showed that cases were signifi cantly more likely to live in unscreened houses than were controls (Mc Nemar chi(2)=56, 1 df, P<0.0001). Despite being generally accepted, an association between insect screens and a reduced incidence of mosquit o-borne diseases has not previously been demonstrated in Australia. We speculate that unscreened housing facilitates the initial spread of a dengue epidemic.