American Samoa has declared a public health emergency amid fears of a deadly measles outbreak.
It follows a young girl testing positive to the viral infection, and a further 31 probable cases being investigated.
The announcement prompted its nearest neighbour, Samoa, to impose travel restrictions on Wednesday.
From Monday, people arriving from American Samoa must show proof of a measles vaccination, while accompanying children under two years of age must have had at least a single vaccine dose.
Suspected cases include children who had been hospitalised, but were under six months old and ineligible for the vaccine.
"We are closing all of our schools," American Samoa's chief epidemiologist, Scott Anesi, said.
"We started the first round of closing the childhood education centres, as well as the child daycare centres.
"We are now moving into all the elementary schools and wrapping up our mass vaccination campaign."
The US territory has a 91 per cent vaccination rate, and health officials are visiting communities to track the spread of the disease.
Active cases 'doing well'
Dr Anesi said all current cases were "stable and doing well".
"With measles, the first four to five days are crucial so our clinical team are evaluating them but so far all are doing well," he said.
The goal was to get all school children, from grade 1 and above, fully vaccinated in order to reopen schools.
"All schools are required by law to check the vaccination status of children enrolled in schools above grade one."
Non-essential government services and inter-island ferries have been closed, and residents were placed under a dawn-to-dusk curfew while unvaccinated people have been told to place a red flag on their homes.
"The main response now is clinical investigations, contact tracing to identify active cases that are symptomatic in the community, get them tested, cared for, isolated and try to stem the flow of community transmission."
Dr Anesi acknowledged the public health response was being set back by a lack of local laboratory testing, which meant samples of probable cases had to be sent to the Hawaii State Laboratory for analysis.
"We are discussing turnaround times [at the Hawaii State Laboratory ]," he said.
"We will know more about this outbreak by the end of the week."
A highly contagious viral infection
In 2019 Samoa staged a two-day lockdown to contain a measles epidemic that killed at least 81 people, most of whom were children.
Dr Anesi said they were treating the response as if "we would have widespread community transmission".
"In low-vaccinated populations, one person can spread measles to as many as 18 people," he said.
"That is why we have shut down schools, are limiting gatherings and working with the community."
According to the World Health Organization, measles is particularly deadly among children under the age of five.
The highly contagious viral infection killed millions of people each year before vaccination rates improved.
American Samoa is home to 50,000 people, including a large US military community.
ABC/AFP
