 This trial is evaluating the use of insect repellent 20 diethyltoluamide to reduce incidence of malaria, Japanese Encephalitis and Dengue. The investigators will recruit up to 1000 households from 100 villages in rural Laos. In each house the investigators shall recruit up to 5 individuals. Half of households will be randomised to repellent, half to a placebo. All individuals will be provided with insecticide treated bed nets for use at night. All household occupants will be followed for 7 months to record malaria cases by Rapid Diagnostic Test every month. Blood spots will be collected at start and end of study to measure Japanese Encephalitis and Dengue. All positive cases will be promptly treated. Outcome will be reduction in number of malaria cases primary outcome and DengueJapanese Encephalitis secondary outcomes. 