Does Mosquito ShieldTM reduce the incidence of ABV infection, as measured by DENV specific neutralizing antibodies, in children >=4-16 years of age whose sero-status to dengue at baseline is seronegative, indicating they have never been exposed to dengue, or monotypic, indicating positive antibodies to a single DENV infection?

The study will be conducted in clusters of households, who will be selected from three Medical Officer of Health (MOH) areas in the district of Gampaha: Negombo, Wattala and Kelaniya.

A total of 14,430 total subjects across 3,900 households will be enrolled for monitoring for active disease – labeled the ‘febrile surveillance cohort’. These households will form 30 clusters (15 allocated to intervention, 15 allocated to placebo control), each containing ~187 houses. A subset of this cohort, 3,570 (110-120 per cluster) subjects aged >=4-16 years that test seronegative (naïve) or positive to a previous single dengue virus (DENV) infection (monotypic) at baseline sampling will also be enrolled for measuring DENV infection based on laboratory-confirmed seroconversion – labeled the ‘longitudinal cohort’ All participating houses in each cluster will be monitored entomologically for adult Aedes aegypti surveys for 3 months before deployment of the spatial repellent (SR) intervention and monthly after the intervention is in place. Entomological surveys will include monitoring of indoor Ae. aegypti adult population densities and blood-fed status.

Mapping of the study area and census measurements: Prior to enrollment, all structures in the study area will be mapped using GPS coordinates and assigned a unique Household Identification Number (HIN). SR Intervention: The SR will be a new formulation of transfluthrin. This active ingredient (AI) is widely used in mosquito coils and other household pest control products worldwide. The new formulation is a passive emanator that will release the AI over a period of up to four weeks, Mosquito ShieldTM. The emanator will consist of a pre-treated piece of cellulose acetate or other medium, which will be positioned within consenting households according to manufacturer specifications of 2unit/9m2. A placebo product of matched design with inert ingredients will be applied similarly. Each Mosquito ShieldTM received directly from industry partner(s) will have a Unique Identifier Code (UIC) identifying the contents as having the AI or blank/placebo. Industry partners will ensure that the listing of UICs is accurate and kept strictly confidential. The intervention will be carried out for 24 months. Both SR and placebo interventions will be replaced every 4 weeks throughout the 24 months of follow up with intervention.

The external statistician serving on the Data Safety Monitoring Board (DSMB) will use a random number generator to assign clusters to SR or placebo treatment arm. All households within the intervention arm (randomly chosen) will be assigned active products with all houses within the control arm (randomly chosen) receiving blank/placebo. Both participants and study staff will be blinded as to whether a study cluster is receiving the active SR or placebo product.

LONGITUDINAL SEROCONVERSION Individual Level Inclusion Criteria: >= 4 – 16 years of age Plans to stay in residence and/or study area for a minimum of 24 months Resident of household or frequent visitor (~20% of day hours in house / month)

FEBRILE SURVEILLANCE Household Level Inclusion Criteria: • Adult head of households agrees to census, health visits and logging resident symptoms when febrile (or in the case of suspected Zika in the absence of fever, presenting with rash, arthralgia, arthritis or non-purulent conjunctivitis). • Individuals spend a minimum of 4hrs per week during the daytime hours or sleep in the house.

FEBRILE SURVEILLANCE Individual Level Inclusion Criteria: • >= 6mo of age. • Fever at the time of presentation or report of feverishness within the previous 24 hours or presenting with a rash, arthralgia, arthritis or non-purulent conjunctivitis (suspicion of ZIKA determined by project physician) • Individual who spends a minimum of 4 hours per week within the household or sleeps in the house.

ENTOMOLOGICAL MONITORING Household Level Inclusion Criteria: • Adult head of household agrees to surveys. • Properties where study personnel do not identify a security risk (i.e., site where abusive substances are sold, residents are always drunk or hostile).

SPATIAL REPELLENT INTERVENTION Household Level Inclusion Criteria: • Adult head of households agrees to have intervention applied inside the home and to provide access to team member at 4-week intervals to change products. • Properties where study personnel do not identify a security risk (i.e., site where abusive substances are sold, residents are always drunk or hostile).

LONGITUDINAL SEROCONVERSION Individual Level Exclusion Criteria: • < 4 and > 16 years of age • Plans to leave residence and/or study area within next 24 months • Temporary visitor to household (<20% of day hours in house/ month)

FEBRILE SURVEILLANCE Household Level Exclusion Criteria: • Adult head of households does not agree to census, health visits or logging symptoms of residents. • Households where study personnel identify a security risk (i.e., site where abusive substances are sold, residents are always drunk or hostile). • Sites where no residents spend time during the day (i.e. work 7d a week outside the home).

FEBRILE SURVEILLANCE Individual Level Exclusion Criteria: • < 6mo of age. • No fever at time of presentation or report of feverishness within the previous 24 hours or not reporting with a rash, arthralgia, arthritis or non-purulent conjunctivitis • Individuals who have spent less than 4 hours in the household during the week prior to illness.

ENTOMOLOGICAL MONITORING Household Level Exclusion Criteria: • Adult head of household does not agree to surveys. • Properties where study personnel identify a security risk (i.e., site where abusive substances are sold, residents are always drunk or hostile).

SPATIAL REPELLENT INTERVENTION Household Level Exclusion Criteria: • Adult head of household does not agree to Mosquito ShieldTM deployment or study team access. • Properties where study personnel identify a security risk (i.e., site where abusive substances are sold, residents are always drunk or hostile