An Algoma Public Health (APH) epidemiologist says more sewage samples need to be analyzed for the presence of COVID-19 in Sault Ste. Marie after a sharp rise in the SARS-CoV-2 viral load last week was followed by a sudden drop. Amanda Perri says the increased viral load since March 24 is the highest concentration the health unit in the city has seen since it first started collecting data at Sault Ste. Marie East End Wastewater Treatment Plant with the assistance of PUC Services Inc. in February 2021. A graph on the APH website reflects the pin, but Perri says another data point from March 28 will be included in that graph to show the sudden plunge of the viral load. “This means that this March 24 increase could have been a misfortune, it could have been a data error,” Perri told SooToday on Friday. “We are not really sure, because when we look at sewage, we want to look at a lot of samples to determine if there is a trend.” Sewage samples are collected from the East End treatment plant – which serves 52,000 people in Sault – about three times a week by PUC Services Inc. The samples are then sent to the Health Sciences North Research Institute in Sudbury for analysis. Data also include COVID-19 infections that are not laboratory-confirmed cases. According to the APH, researchers can use trends in viral loads in sewage along with other indicators – namely the number of cases, hospitalizations and the number of people in intensive care – to make decisions about possible interventions. While the findings may provide an estimate of COVID-19 contamination trends in the community, Perri advises the public to be careful when interpreting wastewater monitoring data based on variable short-term and daily intervals. “We want to be careful when interpreting, especially when looking at such short intervals. “That’s why we want to wait for so many samples to come and see this trend – and once we can identify a trend, we can say that there are cases in the community, COVID is out,” Perri said.
Algoma Public Health is participating in the Ontario Wastewater Surveillance Initiative, a $ 12 million research project coordinated by the Department of the Environment, Conservation and Parks.