Frontline emergency hospital staff are being told they should wear surgical masks at all times, in a protocol change prompted by overseas evidence.

Photo: SUPPLIED / Waikato Hospital

The Australasian College of Emergency Medicine, which represents emergency doctors, is updating its guidelines today and wants the support of health authorities.

Its president, John Bonning, said ordinary surgical masks should be worn when dealing with all patients - even those with no signs of the virus.

Higher protection N95 masks should still be used for patients who could have Covid-19, he said.

There has been debate about the effectiveness of the surgical masks which tie at the back of the head and do not fully seal, allowing some air flow at the sides.

Dr Bonning said while they were not perfect, if used well they helped reduce the spread of the virus particularly by those who did not yet have symptoms.

"You certainly shouldn't rely on them in a high risk situation with a patient clearly with Covid disease in front of you but they do reduce transmission between co-workers," he said.

Photo: RNZ Insight/Karen Brown

Overseas, there was evidence colleagues were catching the disease from one another, he said.

"Remember, we're in our Level 4 bubbles at home but healthcare workers are going to hospital and a lot of us are mixing with each other. We're trying to practise distancing at work as well but you do have to get close," he said.

The masks were no replacement for stringent handwashing, gloves and other hygiene measures, he said.

There was no shortage of the basic surgical masks but N95 masks should still be reserved for suspected cases, he said.