Samoa will go under lockdown from Saturday as it faces its first outbreak of COVID-19 after a woman who was about to leave the country tested positive.

Although health authorities have so far found just a single case, it is the first time Samoa has found any unexplained cases in the community and likely points to an undetected outbreak that has been going on for days or even weeks.

A government report leaked online indicates the woman had visited church services, a hospital, stores, a library and a travel agency since first feeling ill last Saturday.

Samoa and several neighboring Pacific island nations were among the last places on earth to avoid virus outbreaks. But the more transmissible omicron variant has changed the equation, and one by one the island nations have been succumbing to COVID-19.

Since the start of the year, Kiribati, Tonga, the Solomon Islands, the Cook Islands and American Samoa have all experienced their first big outbreaks.

John Fala, who runs a logistics company in Samoa, said it was inevitable that Samoa would eventually get the virus, a reality brought home for many when COVID-19 began spreading in nearby American Samoa.

"We've had two years to prepare," Fala said. "Now it's finally here. Of course, there is going to be a bit of scrambling."

From midnight Saturday, all schools will be closed, public gatherings will be banned, and all stores and other services will be shut down, except those considered essential. From midnight Friday, people were required to wear masks and use vaccination cards.

There were reports Friday of panic-buying ahead of the lockdown.

Fala, who is vaccinated, said his company is considered an essential service and he's frantically trying to navigate the new rules to keep it operating.

The lockdown is initially scheduled to last through midnight Tuesday although Fala expects it will be extended.

The father of three young children, Fala said his biggest concern is that unvaccinated children will catch the virus. He said the nation of 200,000 had good rates of inoculation among adults but had only just begun vaccinating children aged 5 to 11 in the past week or so.

About 65% of all Samoans have had at least two doses of a coronavirus vaccine, according to Our World in Data.

Samoa's Prime Minister Fiame Naomi Mata'afa told people about the positive case in a special announcement to the nation late Thursday. She said the infected woman was in isolation and that her movements and contacts with people were being traced.

Mata'afa said officials wanted to do all they could to contain it from spreading rapidly.

"Although our country continues to traverse through these difficult times, let us continue to trust in the Lord," Mata'afa said in her announcement.

Samoa has had previous virus scares and lockdowns after returning plane passengers tested positive while isolating, but had managed to avoid any community outbreaks until now.

Micronesia, the Marshall Islands and Nauru are among the few remaining Pacific island nations to have avoided omicron outbreaks.