There are now 49 confirmed cases of zika virus in the Cook Islands and as many as 630 people are believed to have suffered from the mosquito-born disease.
Last month health authorities first thought they were dealing with dengue fever but the first batch of test results confirmed 18 cases of zika.
The Director of Community Health Services Dr Rangi Fariu says further results from French Polynesia, where the disease first broke out in the region, take the number to 49.
He says scientists there are still determining the exact nature of the strain.
"Tahiti just asked for those who were already shown positive, they wanted more samples to find out if the zika strain that we have here is similar to the one that they have in Tahiti."
Dr Rangi Fariu says doctors have reported about 630 cases of suspected zika virus in the Cook Islands, and says the real number would be much higher.