Public health units across Ontario are raising concerns about a sweeping amalgamation of their services planned by the province, saying the changes could affect the delivery of programs and lead to layoffs.

Dr. Robert Kyle, president of the Association of Local Public Health Agencies, said the units have so far received only "high level" information from the government about the consolidation of 35 units into 10 -- a process set to get underway later this year.

The planned transformation comes as the government lowers its public health spending, requiring municipalities to contribute millions more to their health budgets than anticipated. By 2021-2022, the provincial cut is expected to be $200 million annually.

The situation has chief medical officers of health across Ontario worried about disruption to essential public health service delivery, Kyle said.

"While all of this is happening, we have to continue to provide programs and services," he said. "It's almost akin to having an auto mechanic fine-tuning a car that's still running."

Ontario's public health units co-ordinate services including vaccination programs, infectious disease outbreak investigations, and restaurant inspections.

It's unclear if the amalgamation exercise will result in savings, but it could result in layoffs since frontline staffing makes up a significant portion of agency budgets, Kyle said.

The government has said it conducted a review of the province's public health units and believes the current structure does not allow for consistent service delivery.

Amalgamating the current 35 units into 10 entities by 2020-21 will help strengthen the system, the Tories said, but discussions with the agencies and municipalities are underway to work out the specifics.

"Nothing is carved in stone at this point," said Health Minister Christine Elliott. "There is a lot of consultation yet to happen."

The consolidation will nonetheless mean that health units will have to serve larger geographic regions, which include communities with different needs. Northern Ontario's nine health units will be reduced to two -- one in the east and one in the west.

The chief medical officer of the North Western Health Unit, which will likely have to merge with the Thunder Bay Health Unit, said her agency serves a predominantly rural population with different needs than other parts of the province.

Many residents have limited access to family doctors so public health fills a gap in primary care, said Dr. Kit Young Hoon. She worried that some of that customized programing could fall by the wayside under the new system.

"That's the main issue, is that the local voice gets lost once you start moving towards larger entities and bigger organizations," she said.

Meanwhile, the Simcoe Muskoka District Health unit said it has been told it will be split into two as a result of the amalgamation. The change will see Simcoe residents served by a new agency with York Region, and Muskoka residents fall under a new North East health unit, which will stretch all the way to James Bay and Hudson Bay.

The agency's chief medical officer of health, Dr. Charles Gardner, said the Simcoe Muskoka unit would like to see its entire service area shift south, rather than be broken into pieces.

"We doubt very much (Muskoka residents) would get the same degree of support by going to the north ... with resources stretched over a much greater territory," Gardner said. "It'll cost more time, more resources and probably more money in the transition because of the complexity of it as opposed to simply staying together and going to the south."

Staff are preparing for the change based on verbal direction from the government but need more information from the ministry, Gardner said.

Public health units in Southwestern Ontario could also shift greatly under the government plan, with five units expected to be merged into one large agency that will cover an area stretching from Windsor to Sarnia to London.

The head of the London-Middlesex Health Unit said he was staying optimistic about the change but acknowledged it would create challenges in how services are delivered, "The hardest part will be that this all happens in a shrinking funding envelope," he said.

"We do important work. One of the top areas of focus will have to be ensuring that we're able to meet the core mandate and support our excellent staff to do their work in an environment that's changing dramatically and shrinking as well."

The president of the Ontario Nurses' Association, which represents nurses at a number of the health units, also raised concerns about the amalgamation in a letter to members over the weekend. Vicki McKenna said Premier Doug Ford did not ask the association's advice before moving ahead with the "unnecessary downsizing."

"We would have told him the truth: skimping on public health will make people sicker and drive up health care costs," she said.