More than sixty people have contracted type one dengue in Rarotonga in the Cook Islands since late February.
The illness, which is transmitted by mosquitoes, has symptoms that include fever, headache and muscle pain.
The Cook Islands secretary for health, Dr Roro Daniel, says the nine people that have been hospitalised are all in a stable condition.
"It has been traced back to somebody who has come from outside the country. The number of cases is slow, we see around two cases a day, some of them are admitted, but some of them are sent home on oral treatment."
Dr Roro Daniel says health officials are running awareness campaigns and are encouraging people to destroy all mosquito breeding sites, such as water containers.