The zika virus infection has reached the Cook Islands for the first time with as many as 175 people displaying symptoms.
Cook Islands health authorities first thought they were dealing with dengue fever but the first batch of test results confirm 18 cases of zika, which is caused by the same family of viruses.
They are waiting on about 40 more test results from French Polynesia, where the mosquito-born disease first broke out in the region before spreading to New Caledonia.
The Director of Community Health Services Dr Rangi Fariu says it was brought back to Rarotonga by someone who visited Tahiti.
"We have been vigilant about spraying all the planes that come in from Tahiti but unfortunately there are some who get the disease or virus in their own country but come here and get sick and certainly that was the case."
Dr Rangi Fariu says 165 people on Rarotonga have zika-like symptoms and 10 on Aitutaki.
He says no one has been hospitalised so far and most people recover within a week.