The union representing seafarers and port workers says the latest case of COVID-19 in a New Zealand port is a concern, but the problem has a solution.

A crew member aboard the Pan Gloris currently in the Port of Tauranga tested positive for COVID-19 this week. As a historical case, they were no longer infectious.

Maritime Union of New Zealand National Secretary Craig Harrison says overseas ships are a key risk when it comes to border security in a pandemic.

He says there is one simple answer that could help: boosting the role of New Zealand domestic coastal shipping.

The Bay of Plenty District Health Board has investigated and confirmed that it was an historical case and not infectious, says a Port of Tauranga spokesperson.

'The crew haven't left the ship since they arrived so there is no risk to the community.

'All port workers who have interacted with the ship have taken the usual precautions.”

The Maritime Union is campaigning for domestic cargo between New Zealand ports to be carried by New Zealand flagged and crewed vessels.

Under current laws, international ships are allowed to move domestic cargo between New Zealand ports.

If international ships made less calls, and just came into major ports with international cargo, it would reduce the chances of infection, says Craig.

He says this a strong argument for a hub and spoke model, where New Zealand coastal shipping moved domestic cargo between regional ports and international hub ports.

Mr Harrison says it is a major concern for maritime workers that they are exposed in a more direct way to COVID-19 than other New Zealanders.

The problem was not with overseas crew, many of whom have been stuck on ships for months without a break, but the system, he says.

The Pan Gloris is expected to leave as scheduled on Sunday.