York Region stands to lose reliability in its warning signs for population-wide COVID-19 and influenza cases as provincial wastewater surveillance ends, public health said.

The Ontario government announced it is ending the program, which allowed public health units to track COVID-19 in wastewater sampling sites across the province, on July 31.

York Region associate medical officer of health Dr. Sarah Erdman said the tool was very useful to help inform public health decisions.

“Given tighter testing eligibility for COVID-19 and influenza, wastewater surveillance provided helpful information about the burden of disease and community transmission among the general population,” Erdman said. “It also provided an early warning of surges ahead of an increase in cases and hospitalizations; without wastewater data, York Region will be unable to reliably obtain these estimates moving forward.”

The program began in 2020 to address the onset of the COVID-19 pandemic. Since then, York Region and other public health units have regularly updated wastewater surveillance data to highlight trends in the transmission of infectious diseases.

“It helped us detect emerging threats,” Erdman said. “We found the tool to be very useful.”

The change means that region-specific wastewater tracking will no longer be available. Public health units were able to upload and access information on a provincewide dashboard and could see disease signals in wastewater up to two weeks before cases would show in the population.

Other public health researchers and agencies have decried the move.

“It is really unfortunate because I think the rest of the world is certainly embracing this (science), so I’m not quite sure why they’re not continuing this very important infectious disease surveillance tool let alone for COVID, but also for influenza and other infections,” said Dr. Colin Lee from the Simcoe Muskoka District Health Unit.