N.B. wastewater data suggests some COVID-19 cases went undetected in 2021
CBC
Public Health officials have raised questions around whether some COVID-19 cases in New Brunswick went undetected in early 2021, after an apparent mismatch between the amount of COVID-19 appearing in wastewater and the province's own COVID-19 testing.
The wastewater data shows four apparent spikes of COVID-19 in 2021: on Feb. 8, March 18, April 29 and June 28, all times when there were "minimal cases or positive tests" reported and PCR testing was widely offered.
The wastewater testing is conducted by the City of Moncton, which has a partnership with Dalhousie University, and is provided to New Brunswick Public Health. CBC News obtained a copy of the test results, and discussion within the Department of Health about the results, through access to information.
Emails from this past April show health officials tried to find an explanation for the differences in the 2021 data, such as increased occupancy at hotels around March break, a difference in the boundaries between the health zone and the area covered by the wastewater treatment plant, and the role of temporary foreign workers who were quarantining in local hotels.
But they couldn't find an easy answer.
"The points that you have mentioned are all things that we have considered, but things do not seem to be lining up," Shannon LeBlanc, the manager of surveillance for the Department of Health, wrote in an April 7, 2022 email.
"We have taken into accounts cases in areas outside of Moncton, and cases among the temporary foreign worker population. It is possible that we had cases that went undetected (how many is not clear)."
No one from Public Health was made available for an interview to explain the apparent mismatch.
In an emailed statement, Department of Health spokesperson Valerie Kilfoil said the government is still assessing the benefits of the wastewater testing pilot in Moncton.
"The materials provided to you should be considered working documents – not a formal surveillance program by the province," Kilfoil wrote.
She didn't provide any explanation about why the data seemed to show some cases of COVID-19 went undetected.
Raywat Deonandan said the province shouldn't dismiss the wastewater results.
"It is so objective, more so than PCR testing, that I think we have to hang our hats on it more confidently," said Deonandan, who is an epidemiologist and associate professor in the faculty of health sciences at the University of Ottawa.
Without widespread random testing, which can capture people who are asymptomatic, Deonandan said it's common to under-detect COVID-19 cases.
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