Tonga will enter a lockdown on Wednesday after finding coronavirus infections in two port workers helping distribute aid arriving in the Pacific nation following a volcanic eruption and tsunami.

The urgent announcement by Prime Minister Siaosi Sovaleni appeared to confirm fears that accepting the aid following the disaster last month could usher in a second disaster by bringing Covid-19 into a nation that had been virus-free.

The volcanic eruption and tsunami last month tainted drinking water, severed communications and left dozens homeless. Three people died in Tonga and two in Peru after the tsunami crossed the ocean.

Ships and planes from Australia, New Zealand, Japan, Britain and China have been delivering aid. Those nations had promised to drop off their supplies of fresh water and medicine without coming into contact with anybody on the ground in Tonga, which usually requires incoming travellers to spend three weeks in quarantine.

But the threat was underscored when dozens of sailors aboard the Australian aid ship HMAS Adelaide reported infections after an outbreak. Crew members aboard aid flights from Japan and Australia also reported infections.

News site Matangi Tonga reported that the positive test results came after officials tested 50 front-line workers at the port. The lockdown was open-ended, the site said, with updates expected from health officials every two days.

Since the pandemic began, Tonga had previously reported just a single case of the virus when a Church of Jesus Christ of Latter-day Saints missionary returning from Africa tested positive in October after flying home via New Zealand.

Tonga and several other small Pacific nations, including Kiribati and the Solomon Islands, were among the last places on the planet to have avoided any virus outbreaks, thanks to their remote locations and strict border controls.

But that has changed in the last few weeks as their defences appeared no match against the highly contagious Omicron variant.

The lockdown in Tonga comes as many homes and businesses remain without internet access after the tsunami severed the sole fibre-optic cable that connects the country to the rest of the world. Officials are hoping repairs will be completed within a week or two.

About 61% of Tonga’s 105,000 people are fully vaccinated, according to Our World in Data.