Four community cases reported in New Zealand overnight, including an Auckland hospital worker, brings the total to five.
Cases are all linked to Tuesday's first case in Auckland, which is confirmed as the Delta variant.
"While the epidemiological variance and transmission link for the community case in New Zealand is still being investigated, we must act swiftly here to minimize exposure risk for the Cook Islands so we remain safe," said prime minister Brown.
The prime minister has announced the Cook Islands will move to Alert Level 2 effective midnight August 16, 2021.
Cook Islands News reports the alert level change will mean that international inwards passenger arrivals for 72 hours through to Thursday are suspended.
This pause on international arrivals will allow Te Marae Ora Ministry of Health to test arriving passengers from 11 August.
This also means domestic travel to the Pa Enua from Rarotonga is suspended for 72 hours also.
Passengers can return to New Zealand from Rarotonga. Passengers from Pa Enua or outer islands can return back to Rarotonga.
"This is a good time to remind ourselves of the need to practice good hygiene measures, and to actively tag in with Cooksafe and Cooksafe+," Mark Brown said.
Cook Islands Cabinet will meet again today to consider new updated information received and next steps.