British and Australian navy ships have arrived in Tonga to deliver aid without making contact with anybody ashore, to avoid spreading COVID-19 in a nation which has never had an outbreak.

The danger of spreading the disease was underscored when nearly two dozen sailors aboard the Australian ship HMAS Adelaide were reported infected on Tuesday, raising fears they could bring the coronavirus to the small Pacific archipelago devastated by an undersea volcanic eruption and a tsunami on Jan. 15.

Since the pandemic began, Tonga has reported just a single case. It is one of the few countries in the world currently completely virus free.

About 61 per cent of Tongans are fully vaccinated, according to Our World in Data.

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Meanwhile, the US has announced it will provide an additional $US2.5 million ($3.5 million) in humanitarian assistance to Tonga through the US Agency for International Development. The aid is in addition to an initial pledge of $US100,000 ($140,000).

Britain said its ship the HMS Spey arrived with 30,000 litres of bottled water, medical supplies for more than 300 first aid kits, and basic sanitation products. It said none of its sailors disembarked the ship, and instead moved the supplies ashore by crane.

The Australian government said its ship had completed the 3300-kilometre voyage from Brisbane and would deliver supplies without contact with the local population to avoid infections.

With restoration of the drinking water supply a major priority, the ship has brought a desalination plant. It’s also carrying helicopters and engineering equipment.

Australia said it was widening its disaster support to include restoration of power and communications.

Under pandemic measures, Tonga typically requires visitors to quarantine for three weeks on arrival, which has complicated the international disaster response. All international aid is to be delivered without local contact.

Tongan authorities have been wary that accepting international aid could usher in a bigger disaster than the huge eruption of the volcano. The subsequent tsunami killed three people.

The ship is the second aid mission from Australia in which at least one crew member tested positive. A C-17 Globemaster military transport plane was earlier turned around mid-flight after a person aboard was diagnosed with the virus.

-AAP