Notes from the Field: Dengue Outbreak — American Samoa, 2025–2026

Dengue is a febrile illness caused by four distinct dengue viruses (DENV-1, DENV-2, DENV-3, and DENV-4).The virus is transmitted by infected Aedes mosquitoes (1).In 2025, several countries and territories in the Western Pacific Region experienced dengue outbreaks (2), and on June 20, 2025, American Samoa, a territory of the United States located in the south Pacific Ocean, reported its first positive dengue test result in 2025.Two weeks later, on July 8, American Samoa declared a public health emergency after identifying six dengue cases, including two locally acquired cases and four associated with travel to neighboring Samoa, where a large dengue outbreak was ongoing (3,4).Recent dengue outbreaks in American Samoa were associated with DENV-4 (2009), DENV-3 (2015), and DENV-2 (2016-2018) (5).After the 2016-2018 outbreak, American Samoa implemented confirmatory laboratory dengue testing on the island.* Including nausea or vomiting, rash, headache, eye pain, joint pain, muscle aches, leukopenia, thrombocytopenia, abdominal pain or tenderness, extravascular fluid accumulation, mucosal bleeding, liver enlargement >2 cm, or increasing hematocrit level (CSTE case definition).† InBios DENV Detect NS1 ELISA Kit; InBios Dengue Detect IgM Capture ELISA kit; and BioFire Defense Global Fever Panel