The Ministry of Health in the Cook Islands says not enough people have taken up free chlamydia treatment in Rarotonga.
The mass treatment for chlamydia started last week.
The Ministry's Director of Public Health, Rangi Fariu, says the programme has been extended a week as only half the targetted number of people was reached.
"We have gone through all the schools, all the work places in the communities, at the market places, and we are going to do that again this week. So far we have treated just over 3,000 people and we will continue on until we reach close to 6,000."
Dr Fariu says the youth rate of chlamydia is high in the Cook Islands.
He says a Ministry of Health study done four years ago found between 35 and 40 percent of people under 25 years old are infected.