A New Zealander who is an international authority on coronaviruses says he favours wearing masks in the right situation to prevent the spread of COVID-19.

Gary McLean is a professor in molecular immunology at London Metropolitan University and also a researcher with Imperial College. He's an international authority on coronaviruses.

He says masks are only needed in high risk areas, such as indoors when you are in prolonged contact with people.

But he says obviously if you are at a restaurant you need to take the mask off to eat.

Gary is currently in Italy and says there they only wear masks indoors.

"So if you go into a bar to have a cappuccino or anywhere inside you must wear a mask, and everyone does, they really are compliant here.

"As opposed to the UK where it has been a guideline now for a number of weeks, the number of people who wear masks is much much lower. I think it's an altruistic phenomenon to wear a face mask.

"So if you go into a bar to have a cappuccino or anywhere inside you must wear a mask, and everyone does, they really are compliant here.

"As opposed to the UK where it has been a guideline now for a number of weeks, the number of people who wear masks is much much lower. I think it's an altruistic phenomenon to wear a face mask."

He says he favours wearing masks in the right situation.

"It's when you're in prolonged inside contact with numerous people is the problem, so taking a train might be the right place to wear them."

Gay says there has been a lot of back and forth on the issue of whether or not to wear face masks.

But he says governments in Europe are now starting to mandate their use in specific situations.

"Obviously healthcare workers wear them for a reason and I'm not convinced there's too many undesirable consequences of wearing a face mask.

"At the very least wearing them will remind you, the wearer, to be careful, it can obviously avoid you touching your face, nose and transmission of virus that way that you may well have picked up from a surface.

"And if you're asymptomatic but shedding virus, the mask should minimise potential transmission."

Gary says it is good to be cautious and just wear one.

"I don't see how it's going to do any harm, I mean people might get a little bit annoyed at the lack of freedom, being told what to do, wear a face mask, but if everyone does it it will minimise transmissions."

Mask wearing may not be completely necessary in countries with very low rates of COVID-19 transmissions and there are also exceptions for very young children and other people with breathing problems, he says.

"But that's not the majority of people, so I think the more people you get to wear them in the right situation, helping each other out, I think it's just probably a good thing to do."

Gary says with no vaccine the world is likely to be living with outbreaks of COVID-19 for a long time with localised lockdowns continuing to be necessary.

He says there is no reason why New Zealand cannot again achieve the elimination of COVID-19.

"But this test, trace, isolate system is going to need to be very very sharp to remain virus-free and we've seen what's happened in the last few days."

The border will have to reopen at some point and monitoring arrivals is the key, he says.

"But we see just how easy it is for those new cases to appear, the way the virus circulates, you just don't know and then before you know it 20-30 cases that can amplify from there, it's frightening."

-RNZ