American Samoa's Successful Dengue Outbreak Response Utilizing Advanced Targeted Residual Spraying Against Aedes Mosquitoes

Pago Pago, American Samoa - The American Samoa Department of Health (DOH), through technical assistance from the Pacific Island Health Officers’ Association (PIHOA) Secretariat, successfully and effectively scaled up vector control operations during the ongoing dengue outbreak, with a special focus on targeted residual spraying (TRS) – a highly effective intervention for suppressing the dengue vector mosquitoes.

As dengue cases continue to rise, TRS is being rapidly deployed to disrupt transmission, primarily in areas where dengue cases are reported, such as households with dengue cases. As a preventive measure, TRS is being used in high-risk schools, workplaces, community health centers, and the Lyndon B. Johnson Hospital. Unlike space spraying, which provides short-term knockdown, TRS leaves a long-lasting insecticidal barrier on surfaces where Aedes aegypti and Aedes polynesiensis commonly rest, giving communities extended protection. 

What Targeted Residual Spraying Does



TRS treats key indoor and peri-domestic resting surfaces, including under tables, behind doors, in shaded outdoor areas, around water containers, and on walls near human activity. This method:

• Provides up to 6 months of protection, depending on the type of insecticide used and the surface type
• Targets the resting behavior of Aedes aegypti, which prefer indoor and shaded areas where traditional fogging may not reach
• Reduces adult mosquito survival, lowering the chance of mosquitoes living long enough to acquire and transmit the dengue virus
• Limits unnecessary chemical use by focusing on epidemiologically relevant areas rather than blanket spraying

Technical Support for TRS Implementation



The PIHOA Secretariat, in coordination with the U.S. Centers for Disease Control and Prevention (CDC) and other partners, continues to provide specialized support for TRS operations, including:

• Training DOH Environmental Health and vector control teams on safe mixing, application, QA/QC, and monitoring of residual insecticides following American Samoa EPA guidelines
• Developing site-specific TRS plans based on case investigation data, mosquito behavior, and environmental conditions
• Ensuring proper insecticide selection and procurement, aligned with Integrated Pest Management standards and resistance profiles of Aedes mosquitoes in American Samoa



In addition to TRS implementation technical support, the PIHOA Secretariat has also been assisting the American Samoa DOH to procure Dengue testing kits, PPEs, household mosquito repellant and emanators, and other critical supplies to support response and community protection efforts. 

Why TRS Matters in American Samoa’s Current Outbreak



American Samoa’s unique housing, indoor mosquito resting habits, and high human–mosquito contact make Aedes mosquitoes difficult to control using source reduction alone. TRS provides a synchronized, localized approach that directly protects households with confirmed or suspected dengue cases, reduces the mosquito population’s ability to sustain transmission, and creates protective zones in neighborhoods with rising case clusters.

“Targeted residual spraying is one of the most effective tools we have for interrupting dengue transmission in households and communities,” said Aileen Solaita, American Samoa DOH’s Director of the Environmental Health Services Division. “By working closely with partners like PIHOA and American Samoa Community College, we are ensuring American Samoa has the technical capacity and operational support needed to apply this method safely and strategically.”

This work is fully supported by funds made available from the U.S. Centers for Disease Control and Prevention (CDC) of the U.S. Department of Health and Human Services (HHS), through PIHOA’s Partnership Cooperative Agreement OT21-2101: Strengthening the Public Health Systems in the US-Affiliated Pacific Islands. The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement, by CDC/HHS, or the U.S. Government.