Public health authorities have long known that Covid positive test results have been under-reported since New Zealand switched to self-conducted rapid antigen testing last year.
That low return rate for test results has become a problem now that a second wave of Omicron cases is sweeping the country.
The official case number for the Te Whatu Ora Southern (the former Southern District Health Board) area yesterday was 895, down from 1045 on Thursday.
"Case numbers in Southern are about the same as they were back in March [the first Omicron wave] and wastewater testing is showing us that potentially more than half of people with Covid-19 in Southern are not reporting their infection," Te Whatu Ora Southern (TWOS) medical officer of health Susan Jack said.
"Reporting your result gives healthcare teams the information we need to plan and distribute resources where they are needed the most."
Reporting a positive test also meant patient wellbeing could be monitored and people could have appropriate care and support arranged quickly, Dr Jack said.
The spiralling number of cases in the past fortnight had been mostly older people, and the biggest jump in cases had been in people aged 45 and over, she said.
Case numbers in younger demographics, especially preschoolers and school pupils, would likely ease due to the school holidays, but planners expected to see cases rise again among children in a week once the winter break was over, Dr Jack said.
"People are getting reinfected, so please, even if you have already had Covid-19, wear a mask when you are out in our communities," she said.
"Something as simple as wearing a mask could protect you and your loved ones from serious illness."
There was another big jump in the number with Covid in hospital in the region yesterday, the figure at 49.
Of those, 23 were in Southland Hospital — which remains closed to visitors after multiple Covid exposure events — 21 were in Dunedin Hospital, one was in Gore Hospital and Oamaru and Dunstan Hospitals had two cases apiece.
None of those patients were in intensive care; it is understand many of them are people who have Covid-19 incidentally, rather than it being the reason they are in hospital.
Southern district interim director Hamish Brown said the dedicated Covid-19 wards at Dunedin and Southland Hospitals were frequently reaching capacity.
"Although there are overflow plans in place, high levels of staff absence due to illness, isolation requirements and vacancies means staffing constraints are putting increased pressure on the health system."
General practices are also being seriously constrained by staff illness and absence, as are private healthcare providers.
Mercy Hospital chief executive Richard Whitney said the Dunedin facility — which opened a new three-bed intensive care unit yesterday — was running at about 85% capacity.
"We are balancing specialist, staff and patient absenteeism on a daily basis," he said.
"We are also active in supporting Health NZ Southern to keep a stream of their elective surgical volume going."
Earlier this week Canterbury — which has more than 100 Covid cases in its hospitals — took the drastic step of cancelling all non-urgent surgical procedures until August 31 to try to maintain enough healthy clinical staff to keep emergency surgical services going.
Mr Brown said TWOS had no plans at this stage to follow the same actions as Te Whatu Ora Waitaha Canterbury.
"This is an evolving situation and will be reassessed regularly."
The latest Health New Zealand Southern regional breakdown of Covid-19 cases showed a more than 500 jump in active cases in the two days since Wednesday.
Of the 5529 active cases in Otago and Southland, 2757 were in Dunedin (up 260), 816 were in Queenstown-Lakes (up 100), 424 were in Central Otago (up 71), 335 were in Southland (up 48), 308 were in Waitaki (up 19) and 194 were in Clutha (up 24).
Invercargill bucked the trend, its 577 cases being 33 down on Wednesday, as did Gore (119, down 48).
Nationally, 10,470 new community cases of Covid-19 were reported by the Ministry of Health yesterday as well as 16 deaths, one of which was in Southern.
There were 773 people in hospital who had Covid-19, 14 of whom were in intensive care.
