Public health units focus on environmental health, communicable disease control, tobacco control and health promotion programmes.
The number of doctors in public health units confronting the pandemic is in crisis, but there is no sign of a plan to fix the situation.
The funding for training registrars to become public health specialists is so limited applicants have had to be turned away.
The College of Public Health has written to Prime Minister Jacinda Ardern warning the situation is critical.
"The Covid-19 response has exposed an extremely concerning reality - that there is a massive and hugely problematic shortfall in New Zealand's public health investment," said the May 4 letter signed by more than 50 public health specialists.
College head Dr Felicity Dumble described it as "incredible insufficient resourcing of public health".
"We appreciate the small increases that we've had recently, but we need them to be larger and we need them to be sustained," she told RNZ.
The country's 12 regional public health units have fewer than 200 doctors to call on.
Public health has been growing at one fifth (9.6 per cent) of the average rate of the other 16 medical specialisations (48 per cent), for a decade, and is the only specialisation falling behind the population growth rate.
Migrant doctors make up 39 per cent of the DHB workforce overall, but only 17 per cent of the doctors in public health.
"Due to the extremely limited funding for training of the registrars, we've had to turn away excellent applicants who would make amazing public health physicians if we had the funding to train them ... and I know of several who I would love to work with," Dumble said.
Des Gorman led attempts to identify then fix the shortages while heading the Government's Health Workforce unit until last year (when the unit, having had its staff numbers chopped, was rolled up into the Ministry of Health).
"It was profoundly frustrating," Gorman, a professor of medicine at Auckland University, said.
"We had no support from the Ministry of Health.
"We had little or no support from the district health boards and we received quite strong opposition from some of the more established medical colleges because they quickly worked out that if more money was going to go to public health and palliative care, that might mean less money for them."
He offered generous subsidies to DHBs to take on more trainees - "one chief executive said to me, 'Not if it costs me a cent'."
He tried to overhaul the whole funding system.
It did not work. A year on, and amid a pandemic, little has changed, he said.
"There is no strategy."
Despite dealing with the flu pandemic of 2009, the fatal Havelock North water contamination of 2016, last year's measles outbreak and now Covid-19 - and all the time delivering health education and disease screening to a growing population - the country's public health teams are getting a third less government funding now than they did a decade ago.
Their funding was nudged up from $403 million to $440m this month in the only government Budget delivered during a pandemic emergency in living memory - but it is still $80m less than it was 10 years ago ($517m).
The Southern District Health Board raised the problem at a board meeting this month.
"This issue has been raised consistently with the Ministry of Health by district health boards over the years, however, it is not until one gets to an event like this that one realises the impact of under investment," the board minutes show.
Southern DHB's public health unit got just over $1m more to combat Covid-19, part of $70m of urgent funding to improve contact tracing.
Gorman said DHBs were part of the problem.
The extra ministry money could not magic up more trained doctors, he added. "What we are looking at now is a three to five year lag time."
Dumble said the extra money was a decent, short-term injection - but asked what of the long term?
The letter to the Government said the pandemic was "the opportunity to move public health service design into the 21st century".
"We must have excellent and collective foresight to plan the services we need to deliver into the future, rather than repeating past mistakes of responding with 'just enough' to see us through the current crisis."
RNZ understands the ministry is now considering extra funding to increase training places. The ministry has been asked for details.
Gorman said there was "every danger" any funding increase would be a one-off.
"I think the Public Health College's view that there needs to be a sustained pipeline of training is absolutely right.
"But I think it needs to be broader than just doctors.
"It needs to be a training pipeline which looks at future need across the entire range of the public health workforce."
Public health units also employ protection officers, nurses and experts in environmental pollution, and the equipping of that workforce was being done "piecemeal", he said.
The letter to the Government called for investment across epidemiology and statistics, geospatial epidemiology, social marketing, informatics, and emergency management, and related specialist areas of occupational health, health protection and drinking water assessment.
Dumble said it was not just staff that were outnumbered by the task; the electronic tools they had to hand also were not good enough.
"Nationally, we need information systems that can capture all our data needs, from clinical and laboratory notification through to case and contact management, as well as real time monitoring and centralised reporting," the letter to the Government said.
Disjointed data systems meant regional public health units lost sight of contact tracing cases sent to the national tracing centre in a "case/contact split", it said.
"This is a stop-gap measure only and should absolutely not be the longer-term approach," it said.
The Health and Disability System Review, which is overdue for release, is expected to comment on if there should be a central public health agency.
The ministry earlier told RNZ it had no plans to restructure the regional units.
"We're aware that during the course of the Covid-19 response there has been a lot of public attention on the role that regional public health units play. Recent funding has strengthened their ability to respond."
Move comes despite no one falling off a float in the 75 years the parade's been running.