A measles outbreak has been declared in American Samoa, a move that will see public schools closed and gatherings in parks banned.

Key points: Neighbouring independent Samoa has been suffering a deadly measles crisis

Neighbouring independent Samoa has been suffering a deadly measles crisis American Samoa will receive vaccines from authorities in the US mainland

American Samoa will receive vaccines from authorities in the US mainland Immunisation rates are much higher than in Samoa but children are still vulnerable

Announcing the outbreak on Friday, the Government said nine cases had been recorded in the US territory.

Five of those infected had been travelling outside the territory.

As for the other four people who tested positive for measles, "we're suspecting that is local transmission, meaning that it's most likely that some of these travellers did transmit the measles virus to them, causing them to be sick," Health Department epidemiologist Aifili John Tufa said.

In the neighbouring nation of Samoa, at least 65 people, mostly children, have died and more than 4,000 people have been infected, since an outbreak started in mid-October.

American Samoa will get a measles vaccine shipment from the US Centres for Disease Control and Protection on Monday, Dr Tufa said.

Data presented by health officials during a Cabinet meeting early this week shows a 99.7 per cent vaccination rate for mumps, measles and rubella in the territory, officials said.

But Dr Tufa said more needed to be done for children aged one to five, for whom the immunisation rate stood at 84.7 per cent.

"The number one way to stop the spread of measles is to immunise," he said.

The developments in American Samoa came after dozens of Hawaii health care workers returned to their homes after voluntarily providing measles vaccinations to thousands of residents of the independent nation of Samoa.

A team of 76 health care workers and support staff went to Samoa for a two-day medical mission to ensure residents were immunised from the highly contagious virus.

The Samoan Government has declared a state of emergency over the measles outbreak. ( Facebook: Government of Samoa )

"You have scores of people dying, and the society is paralysed," Honolulu surgeon Paulus Tsai said. "Basically life has come to a standstill for the island."

Samoa declared a state of emergency and complete shutdown of government and business operations while vaccination teams searched for residents susceptible to the disease, health officials said.

About 34,000 people were immunised over two days, officials said.

"Of all the efforts to save children around the world, immunisation has the most dramatic impact," Dale Glenn, a doctor from Straub Medical Centre, said.

"Everybody came together with their aloha to unite and support Samoa and attack this disease head-on in a way that will make a permanent difference in the lives of the people."

The mission was coordinated by medical doctor and Lieutenant Governor Josh Green who worked with Samoan leaders, the World Health Organisation and the Centres for Disease Control and Prevention, officials said.

AP