Most elective surgery is being postponed in Canterbury as hospitals grapple with Covid-19 staff shortages.
More than 500 of the region's doctors, nurses and allied health staff are off sick with the virus, isolating or caring for whānau.
Hospitals will only do urgent surgery from today, including treating cancer patients and people who have been in accidents or suffered major trauma.
The DHB's Covid-19 controller, Helen Skinner, said staff hoped to be able to do some urgent elective surgery on a case by case basis.
"We do understand this is a distressing time when people have their surgery deferred, so we're making those decisions day by day depending on the staffing that we have to make sure that we maintain safe care for people within our facilities," Dr Skinner said.
"We're not probably at the peak of our cases yet here in Canterbury, so we're going to be needing to make those decisions over the next few weeks."
Some outpatient appointments were also being postponed, she said.
"Many have already been switched to virtual consults and are carried out over the phone or by video call, however we have to postpone more planned in-person appointments this week," she said.
"Urgent outpatient clinics such as dialysis will continue as will urgent and non-deferrable surgery and medical procedures."
People whose surgery or outpatient appointment has been deferred would be contacted by phone, Dr Skinner said.
"We apologise for the inconvenience and stress of having your surgery or appointment postponed at short notice, and hope people appreciate the need to prioritise all our available people resources to ensure safe care for everyone," she said.
Canterbury District Health Board employs about 11,000 staff.
On the West Coast, a "significant cluster" of Covid-19 cases has emerged at the reclusive Gloriavale Christian Community.
District Health Board incident controller Philip Wheble said staff were helping church leaders manage the outbreak.
"This includes providing infection prevention and control advice and resources, and clinical support," he said.
"It is important to remember that there is a national outbreak of Covid-19 and increasing case numbers throughout the West Coast, so everyone should be taking steps to protect themselves, including being vaccinated, masking, and getting a test if they become symptomatic.
"In that context, the DHB advises that there is no additional risk to the general public from this cluster of cases."
The Gloriavale community has traditionally been against vaccinations, but mandates prompted a change of heart to stop its schools closing.
As the Omicron wave rolls down the country, the number of PCR tests being processed has fallen to an average of just over 4000 a day.
Ministry of Health data shows laboratories processed an average of almost 30,000 tests a day late last month.
New Zealand Institute of Medical Laboratory Science president Terry Taylor said the introduction of rapid antigen tests had eased the pressure, along with better public education about when to take a PCR test.
"Staff got absolutely hammered during the later period of February," he said.
"At the moment, it can be a lot more manageable for us in the laboratory setting with the way things are panning out with more responsibility being passed onto the public."
Director-General of Health Ashley Bloomfield has conceded the Ministry of Health overestimated the number of tests labs could process once the virus started to spread.