Tonga is learning to live with coronavirus brought to its shores during aid deliveries following a volcanic eruption and tsunami.

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 will not last too long.

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

Tonga is only one of several Pacific 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 Jan. 15 eruption of the massive undersea Hunga Tonga Hunga Ha'apai volcano, then hit with a tsunami that followed.

Only three people have been confirmed killed, but several small settlements in outlying islands were wiped off the map and the volcanic ash tainted much of the drinking water.

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.

"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.

"We desperately need some good news."

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 might have come into contact with the dockworkers, but the government released a list of locations where the virus could have spread, including a church, several shops, a bank and a kindergarten.

Tonga's prime minister Siaosi Sovaleni imposed an open-ended lockdown starting 6pm on Wednesday.

It 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.

One of the infected dock workers has since tested negative, but remains in quarantine, and 389 others have been cleared of Covid-19, Mr Sovaleni told reporters in Tonga.

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

The government has been primarily communicating with residents by radio addresses, and Mr Fonua said his crews estimate they may have to replace a 54 mile section of undersea cable.

They were hoping to restore service by next week.

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.