Dengue virus detected in wastewater sample from Hawaiʻi Island

A wastewater sample from the Hilo wastewater treatment plant tested positive for dengue virus, according to the Hawaiʻi Department of Health.

The sample was collected on Aug. 24 and the department was notified on Aug. 31, which is when a follow-up sample was collected. The Department of Health is not currently tracking any active dengue cases in Hawaiʻi County.

Dengue virus is transmitted from an infected person to a mosquito and then to another person. While Hawaiʻi is home to mosquitoes that can carry dengue, the disease is not endemic, or established, in the state.

All dengue cases reported in Hawaiʻi to date have been travel-associated. Of the seven dengue cases reported in Hawaiʻi in 2026, all have involved travel to Pacific Island countries and territories.

Dengue is a year-round risk in tropical and subtropical areas of Central and South America, Asia, the Middle East, Africa and several Pacific islands, including American Samoa, the Federated States of Micronesia, the Republic of the Marshall Islands and the Republic of Palau.

Travelers returning from areas with dengue risk should take precautions to prevent mosquito bites for three weeks. If dengue symptoms develop within two weeks of returning, travelers should seek medical evaluation.

Symptoms of dengue can range from mild to severe and include fever, nausea, vomiting, rash and body aches. Symptoms typically last two to seven days. While severe illness can occur, most people recover within a week.

Individuals who have recently traveled and are experiencing these symptoms should contact their healthcare provider. Healthcare providers and individuals who suspect dengue infection are advised to call the Disease Reporting Line at 808-586-4586.

Hawaiʻi collects municipal wastewater samples each week and sends them to the State Laboratories Division for dPCR testing, as well as to the University of Missouri for advanced sequencing to look for bacterial and viral genetic material associated with community infections.

Wastewater sampling is routinely conducted across Hawaiʻi to support infectious disease surveillance. This testing can identify viral genetic material shed by infected individuals, including those who may not yet have symptoms or have not sought medical care.

A dengue signal in wastewater does not confirm a clinical case or indicate community transmission. Instead, it serves as an early indicator that can prompt awareness and monitoring for potential cases.

For more information about wastewater surveillance:

• Hawai‘i Wastewater Surveillance
• WastewaterSCAN Dashboard
• Centers for Disease Control and Prevention Wastewater Monitoring Program

For more information about dengue and mosquito control, visit:

• Centers for Disease Control and Prevention – Dengue
• Hawaiʻi Department of Health – Dengue
• Hawaiʻi Department of Health – Mosquito-Transmitted Diseases
• Hawaiʻi Department of Health – Vector Control