Abstract
Timely and extensive space spraying has been widely used to prevent the spread of dengue fever/dengue hemorrhagic fever (DF/DHF). Field evaluations on its effectiveness have been rarely reported. This study aimed to evaluate the timeliness, coverage, and effectiveness of space spraying for DF/DHF control using a geographic information system (GIS). Longitudinal monitoring of DF/DHF cases and spray activities in Songkhla municipality was done between May 2006 and April 2007. After a case was detected, subsequent cases occurring within a 100 meter radius of the index case's house and between 16–35 days of onset were considered as potential secondary cases. During the study period, 140 cases of DF/DHF were detected. Of these, 25 were identified as secondary infections from 20 index cases. Where a secondary infection occurred, the mean attack rate was 2.7 per 1,000 population. Two significant predictors for being a secondary case were both related to the house of the index case, namely, absence of window screens and being constructed with corrugated iron sheets. Our findings suggest that space spraying in the study area was inadequate and often failed to prevent secondary cases of DF/DHF. Control programs should target houses constructed with corrugated iron sheets.
Highlights
Dengue fever (DF), dengue hemorrhagic fever (DHF), or dengue shock syndrome (DSS) is one of the most important mosquito-borne viral diseases caused by one of four closely related, but antigenically distinct, virus serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), of the genus Flavivirus
This study aimed to evaluate the effectiveness of space spraying for DF/DHF in Songkhla municipality, southern Thailand during May 2006 to April 2007 and to determine the risk factors for secondary DF/DHF cases
All cases were identified under the definition given above; 115 primary cases were classified into 20 index cases and 95 primary cases
Summary
Dengue fever (DF), dengue hemorrhagic fever (DHF), or dengue shock syndrome (DSS) is one of the most important mosquito-borne viral diseases caused by one of four closely related, but antigenically distinct, virus serotypes (DENV-1, DENV-2, DENV-3, and DENV-4), of the genus Flavivirus. The transmission cycle starts when the female Aedes mosquito takes blood from a person during the viraemic phase (acute febrile) of illness and becomes infected with the dengue virus. After an extrinsic incubation period of 8 to 12 days [2], the salivary glands of the mosquito become infected, and the virus is transmitted when the infective mosquito bites and injects the salivary fluid into the blood of another person. Symptoms caused by dengue infection may last 3 to 10 days, with an average of 5 days [3], after the onset of symptoms This is the crucial period when the patient is most infective for the vector mosquito and contributes to maintaining the transmission cycle if the patient is not protected against vector mosquito bites. Infection with one Journal of Tropical Medicine of four dengue virus serotypes does not provide long-term cross-protective immunity, so a person living in a dengueendemic area can have four dengue infections from their lifetime
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