The CDC has a seven member team in the territory helping the Department of Health tackle the Zika virus outbreak.
The number of confirmed Zika cases has climbed to 10, including three pregnant women.
The leader of the CDC team, Dr Thane Hancock, said the mosquitoes that carry the Zika virus bite people outside the homes, don't fly very far and die after two weeks.
But he said before that happens they can lay hundreds of eggs, so eliminating the larvae is vital.
"If we spray and kill the adult mosquitoes there are still all those eggs that will hatch out later on, so instead the real way to shut down the outbreak and reduce the number of mosquitoes is really starting with the mosquitoes at the source where all these young mosquitoes are coming out at places of standing water."