Assessing the burden of dengue among household members in Alaminos, Laguna, the Philippines: a prospective cohort study.

Background: The incidence of dengue is increasing rapidly and is a challenging health issue in the Philippines. Epidemiological data are largely based on a passive-surveillance reporting system, which leads to substantial under-reporting of cases. Objectives: To estimate dengue infection and disease incidence prospectively at the community level in an endemic area of the Philippines using an active surveillance strategy. Methods: We implemented active surveillance in the highly endemic community of Alaminos, Laguna. The study consisted of a 1-year follow-up with 2 visits scheduled at the start and end of the study, as well as regular active surveillance in between and unscheduled visits for suspected cases. Blood samples were collected and analyzed to detect dengue during the first scheduled visit and all unscheduled visits, and clinical examination was performed at all visits (registered at clinicaltrials.gov NCT02766088). Results: We enrolled 500 participants, aged from 6 months to 50 years; 76.2% were found positive for immunoglobulin G (95% confidence interval [CI], 71.9-80.0), with 92.0% among those aged 9-17 years. Active (weekly) surveillance identified 4 virologically confirmed cases of dengue (incidence proportion 0.8; 95% CI 0.3-2.1); all in participants aged ≤14 years. Conclusions: Routine surveillance programs such as sentinel sites are needed to characterize the entire clinical spectrum of symptomatic dengue, disease incidence, and transmission in the community.