The Department of Health in American Samoa says the hospital has noticed a recent rise in the number of patients with dengue like symptoms.
It also says four highly suspect cases have been identified in the last few weeks.
The department says the territory has no record of current cases which suggests the start of an outbreak.
The last outbreak was in 2001 with over 3,000 cases reported at the hospital within a 3-month period.
To prevent another large outbreak in the territory, health officials recommends that everyone should immediately inspect around their homes and clear any debris that may collect water in which mosquitoes can breed.