An outbreak of the Zika virus in the United States has prompted the CDC to begin monitoring more than 6,000 people who have traveled to Puerto Rico.
The agency said Thursday that it will collect DNA samples from more than 1,500 of the more than 10,000 Puerto Rican residents in its quarantine program.
The CDC has not released a complete list of Puerto Rican individuals it will monitor for Zika, although it says they may include those who have had sexual contact with a known Zika virus case.
Puerto Rico has been under a mandatory quarantine since April.
Alejandro Garcia Padilla announced Thursday that he will not seek reelection in 2019, saying he would work with the CDC and other federal agencies to help the island recover.
Padilla has been criticized by some Puerto Ricans for not doing enough to prevent the spread of the virus.
___ AP Writer Alicia Caldwell contributed to this report from Miami.