The deadly virus has almost certainly entered Tonga via infected personnel delivering aid from countries that include Australia, New Zealand, the US, China, France, Fiji and Britain.
Two wharf workers tested positive Tuesday. The Ministry of Health has been testing workers there amid international aid shipments after last month s volcanic eruption.
Exhausted naval technicians claim they are battling temperatures of up to 50deg Celsius while trying to repair a crippled warship which also has a Covid-19 outbreak on board.
A massive electrical power failure has crippled the Australian Navy's largest warship as it completes its humanitarian mission to Tonga after the 14 January eruption.