For more than two years, the isolation of the Pacific archipelago nation of Tonga helped keep COVID-19 at bay.

But last month's volcanic eruption and tsunami brought outside deliveries of desperately needed fresh water and medicine — and the virus.

Now the country is in an open-ended lockdown, which residents hope will help contain the small outbreak, and not last too long.

"We have pretty limited resources, and our hospitals are pretty small," Tongan business owner Paula Taumoepeau said on Friday.

"But I'm not sure any health system can cope. We are lucky we've had two years to get our vax rate pretty high, and we had a pretty immediate lockdown."

Remoteness adding extra pressure

Tonga is only one of several Pacific island countries to experience their first outbreaks over the past month.

All have limited health care resources, and there is concern that the remoteness that once protected them may now make helping them difficult.

"Clearly when you've got countries that have already got a very stretched, and fragile health system, when you have an emergency or a disaster and then you have the potential introduction of the virus, that's going to make an already serious situation immeasurably worse," said John Fleming, the Asia-Pacific head of health for the Red Cross.

Tonga was coated with ash following the January 15 eruption of the massive undersea Hunga Tonga-Hunga Ha'apai volcano, then hit with a tsunami that followed.

The aftermath saw three people confirmed killed and several small settlements in outlying islands wiped off the map, while the volcanic ash has tainted much of the drinking water on the island.

The nation of 105,000 had reported only one case of COVID-19 since the beginning of the pandemic — a Church of Jesus Christ of Latter-day Saints missionary returning to the island from Africa via New Zealand who tested positive in October — and authorities debated whether to let international aid in.

They decided they had to, but despite strict precautions unloading ships and planes from Australia, New Zealand, Japan, Britain and China, two Tongan men who worked at the capital's Queen Salote Wharf handling shipments tested positive on Tuesday.

Battling tsunami aftermath and COVID-19

"Tonga is just out of luck this year," said Samieula Fonua, the chairman of Tonga Cable Ltd., the state-own company that owns the sole fibre-optic cable connecting the nation to the rest of the world.

The two were moved into isolation, but in tests of 36 possible contacts, one's wife and two children also tested positive, while the others tested negative, the local Matangi Tonga news site reported.

It was not clear how many people they might have come into contact with the dock workers, but the government released a list of locations where the virus might have spread, including a church on two days, several shops, a bank on two days and a kindergarten during school hours.

Prime Minister Siaosi Sovaleni told reporters "some" of the five infected had started to show symptoms and were being quarantined at a medical facility.

Most without internet during lockdown

He imposed an open-ended lockdown starting 6pm on Wednesday; one that could be particular arduous for Tongans because most have been without any internet connections since the volcanic eruption severed the fibre-optic cable to the country.

The government has been primarily communicating with residents by radio addresses, and Mr Fonua said his crews estimate they may have to replace an 87-kilometer section of undersea cable.

Still, they were hopeful to restore service by next week.

COVID-19 possibly brought through aid

It is not yet known what variant of the virus has reached Tonga, nor who brought it in.

Officials have stressed that the aid deliveries were tightly controlled, and that it is not yet proven the virus came in that way.

Sailors aboard the Australian aid ship HMAS Adelaide reported nearly two dozen infections after an outbreak on board, but authorities said it had been unloaded at a different wharf.

Crew members aboard aid flights from Japan and Australia also reported infections.

Dock workers test positive

One of the dock workers who initially tested positive has now tested negative, but remains in quarantine, and 389 other port workers have all tested negative, Mr Sovaleni told reporters in Tonga.

But he said Friday that a "primary contact" to one of the people infected had tested positive, and ordered the lockdown extended another 48 hours.

"The people are OK with the lockdown because they understand the reason why, so the corona doesn't spread over our little country," said resident Tulutulu Kalaniuvalu, a 53-year-old former police official who now in private business.

Uphill battle to contain outbreak

Despite the optimism, experience from elsewhere in the pandemic, especially with prevalence now of the rapid-spreading Omicron variant, suggests that Tonga faces an uphill battle in trying to contain the outbreak, according to Indonesian epidemiologist Dicky Budiman.

Some 61 per cent of Tongans are fully vaccinated, according to Our World in Data, but because the country has not yet seen any infections, there will be no natural immunity and it is not clear whether the shots were given long enough ago that they may now be less effective, Mr Budiman said.

The global experience has been that when the virus hits such countries, the number of hospitalisations is very high, he said, recommending that the government immediately start offering booster shots and open vaccinations to younger children.

The October case of the missionary with COVID-19 prompted a wave of vaccinations, and 1,000 people already showed up for a first dose after the current outbreak was detected, Mr Kalaniuvalu said.

Outbreak prompts people to get first jabs

This is already starting to be seen in the Solomon Islands, which reported its first community outbreak on January 19.

With only 11 per cent of its population fully vaccinated, the virus has been spreading rapidly with the Red Cross reporting that less than two weeks later, there are now more than 780 recorded cases and five COVID-19 related deaths.

Elsewhere, Fiji — still reeling from damage caused by Cyclone Cody in early January — has been battling an ongoing spike in cases, fuelled by Omicron, and cases have been reported for the first time in Kiribati, Samoa and Palau.

Palau has nearly its entire population fully vaccinated, while Fiji has 68 per cent and Samoa 62 per cent, but Kiribati is only at 33 per cent.

The key to ensuring hospitals aren't overwhelmed is to make sure more people get shots, Mr Budiman said.

Mr Kalaniuvalu said some people have questioned the decision to let the ships carrying aid into Tonga, but most feel it was necessary to help through the aftermath of the volcano and tsunami, and that the islanders now just had to do their best to minimise the impact of the outbreak.

"To be honest with you, we were one of the luckiest countries in the world for almost three years, now it's finally here in Tonga," he said.

AP