Study setting: Medellin and Bello municipalities, Colombia Health condition(s) studied: Dengue, Zika and chikungunya virus infection Intervention: Deployment of Wolbachia-infected Aedes aegypti mosquitoes in Medellin and Bello.

Study design:

1. An interrupted time-series analysis utilising routine disease surveillance data collected by the Medellín and Bello Health Secretariats, which aims to compare incidence of dengue, chikungunya and Zika pre- and post-Wolbachia release.
2. A test-negative study using an incident case-control design, which aims to quantify the reduction in disease incidence among people living within a Wolbachia-treated zone compared with an untreated zone that has a similar dengue risk profile at baseline.

• Selection and enrolment of participants: Enrolment of patients will commence after completion of Wolbachia releases in the early zones. Study processes for enrolling patients presenting with febrile illness will be established at a network of primary health care facilities that serve the population who reside in the study area. Trained research staff will be employed to assist with study processes in each site. Participants will be enrolled from within the population of patients (aged ≥3 years old) presenting with undifferentiated fever of 1-4 days' duration. All patients meeting the inclusion criteria will be eligible for enrolment and will be asked to provide written informed consent before participating in the study.
• Recruitment procedures: All eligible participants meeting study inclusion criteria will be invited to enroll continuously throughout the study period. Recruitment will occur during normal clinic hours. Participants will be managed according to standard clinical practice by the attending physicians. Recruitment rates in each clinic and across the study site as a whole will be monitored weekly, including a review of the screening logs to identify the proportion of eligible participants who did not consent to participate. The field coordinator will make regular visits to low-enrolling clinics to identify clinic-based, patient-based or other causes for low recruitment, and put measures in place to address these.
• Screening: All patients presenting with febrile illness will be screened against the study inclusion criteria by trained staff. All eligible febrile individuals will be recorded in a screening log and invited to participate. Participation status (consent/decline) will be recorded against each participant in the log.
• Informed consent: Written informed consent will be sought from participants (or their guardian where the participant is a minor) by trained local staff, after explaining the study objectives, processes, data, and sample collection, and the participant has had an opportunity to ask questions. A verbal explanation of the written Explanatory Statement will be provided to all participants in the local language. In addition, participants aged between 7 and 17 years will be invited to sign an assent form indicating they understand the research and agree to participate. Data and sample collection procedures
• Data collection: A unique identifier will be assigned to each participant at enrollment. Basic demographic details, eligibility against the inclusion criteria and illness onset date will be recorded in a standardized case report form.

Inclusion Criteria:

• Fever (either self-reported or objectively measured, e.g. axillary temperature ≥38oC, with a date of onset between 1-4 days prior to the day of presentation.
• Aged ≥3 years old.
• Lived (i.e. slept) in the study area every night (or day) for the 10 days preceding illness onset.

Exclusion Criteria:

• Localising features suggestive of a specific diagnosis e.g. severe diarrhea, otitis, pneumonia
• Prior enrollment in the study within the previous 4 weeks.

The case-control study area as a whole has a population of approximately 564,000, of which approximately half will be resident in areas that receive early Wolbachia deployments ('early-release') and half in areas that will receive late Wolbachia deployments ('late-release').

The study population for measurement of the efficacy endpoint is the population of patients who reside in the study area, presenting to the network of participating primary health care facility with febrile illness, and meeting the eligibility criteria.