Climatic factors associated with epidemic dengue in Palembang, Indonesia: implications of short-term meteorological events on virus transmission.

An extensive outbreak of dengue fever and dengue hemorhagic fever occurred in the city of Palembang, South Sumatra, Indonesia from late 1997 through March/April 1998. All surveyed administrative areas (kelurahan) in Palembang were found to be 'permissive' for dengue virus transmission; and all areas that had Aedes (subgenus Stegomyia) larval mosquitoes in abundance experienced increased cases of DHF during the epidemic. The Aedes House Index (HI) for combined Aedes aegypti and Aedes albopictus was recorded every 3 months before, during, and after the epidemic. Ten surveyed sentinel sites (October-December 1997) immediately preceding the epidemic peak had a combined HI of 25% (range 10-50.8%). Entomological surveys during the peak epidemic period (January-April) showed a combined HI of 23.7% (range: 7.6-43.8%). Kelurahans with the highest numbers of reported dengue cases had an HI exceeding 25%; however, there was no discernable relationship between elevated HI and increased risk of DHF incidence. Despite the unusual climatic conditions during late 1997 created throughout the region by the El Niño Southern Oscillation (ENSO), the house indices during both wet and dry months remained above 23% for the 4 quarterly (3-month) periods surveyed in the second half of 1997 and first half of 1998. Rainfall returned to near normal monthly levels shortly before the reported increase in human cases. However, mean ambient air temperatures continued above normal (+0.6 to 1.2 degrees C) and were sustained over the months leading up to and during the epidemic. Evidence suggests that an ENSO-driven increase in ambient temperature had a marked influence on increased virus transmission by the vector population. We explore the apparent associations of entomological and climatic effects that precipitated the epidemic before the influx of reported human cases.

Enhancing knowledge and awareness of dengue during a prospective study of dengue fever.

In 1992, the Indonesian CDC implemented strategies to control and prevent dengue fever (DF) by including community involvement to reduce larva breeding sites and a mass health education program. To contribute to this effort, we incorporated an educational component into a prospective study of DF conducted at two textile factories in Bandung. This education provided: a lecture on the signs and symptoms of dengue and ways to prevent the disease, posters in the health clinic at each factory and handouts given to each volunteer with an explanation of symptoms. Upon enrollment, each participant completed a questionnaire to gather demographic information. Additionally they were given a brief (non-standardized) test (PRE-test) of their dengue knowledge, which was verbally administered by the study physicians. Five questions (15 point system) were designed to assess the participant's ability to recognize and describe aspects of dengue in lay terms. The subject material included: the symptoms of acute DF, transmission of dengue virus, and basic steps for disease prevention. The same questionnaire was re-administered 18 months later (POST-test), and the results were compared. A total of 2,340 participants completed both the PRE- and POST-tests; there were 1,373 males and 967 females, median age 36 years (range 18-59). Only 0.3% of participants scored EXCELLENT (15-14 points) on the PRE-test whereas 8.4% scored EXCELLENT on the POST-test. Fewer participants scored VERY BAD (2-0 points) on the POST-test compared to the PRE-test (1.4% vs 4.0%). The average raw scores for the PRE- and POST-tests were 7.8 and 10.1, respectively. Improvement of individual scores correlated highly with educational level. No significant correlation was identified for gender, age, factory location or a diagnosis of dengue during the study. These findings demonstrate that our prospective study enhanced knowledge and awareness of dengue in the volunteers.