Multiple waves of winter illness are washing over a health system already under strain, and now the fight is on to keep clinicians' heads above water.

Last night Dunedin Hospital closed all its wards to visitors after patients and staff on several wards were exposed to Covid-19.

There were 26 patients in Dunedin Hospital with the virus on Friday, a rise of more than 60 percent from early last week.

Southern DHB chair Pete Hodgson said considering that environment, closing to visitors made sense.

"The proactivity of the staff is to be admired. They're saying 'We're closing to visitors because we're going to get on top of this'.

"You do need to manage these diseases very assertively and our staff are and I think that's great. I'm fully supportive of it."

Some visitors were still allowed on compassionate grounds.

Hodgson said he understood it would be frustrating for many.

Southern DHB took the same step at Southland Hospital last month, before reopening to visitors a week later.

Minister of Health Andrew Little, who was in Dunedin yesterday to mark the beginning of construction of the city's new hospital, also backed the measure, saying it made sense with the healthcare system battling Covid-19, influenza and other respiratory ills, like RSV.

"All hospitals are having to manage that and manage the risk of infection to other patients and to visitors, so it doesn't surprise me and we're seeing other hospitals taking similar measures. They're all very short-term."

Dunedin Hospital's Covid-19 ward had been running at capacity, and other wards might yet be temporarily used for Covid-19 patients.

Elsewhere in the motu, hospitals were also extremely busy.

Hawke's Bay Hospital had 33 patients with the flu on Friday - more than three times the number on Monday.

Another 14 patients had Covid-19.

In Counties Manukau DHB, the surge of winter illness had come much earlier than expected.

Chair Mark Gosche said Middlemore had been at near-capacity throughout the pandemic.

"We've got lots of winter illnesses impacting us right now. Covid has stubbornly stayed at a level that impacts every part of the hospital ... and the community and primary sector that serves Counties Manukau are feeling a lot of pressure as well."

Clinicians were also fighting illness themselves.

Over recent weeks an average 14 percent of the more than 3500 clinical staff at Wellington Regional Hospital and 4 percent of the more than 1600 staff at Hutt Hospital have been absent.