How many people in Newmarket have had Covid-19 – or have it now? 

I’m sorry. I haven’t a clue.

But, then again, no-one else knows either.

Historic data

York Region’s Covid webpage gives the results for PCR testing (polymerase chain reaction) which the Province transitioned away from on 31 December 2021. The data is historic. 

The official statistics do not pick up the vast majority of Covid cases. People who self-test using the widely available Rapid Antigen kit are not picked up.

The two key metrics

Instead, the Region uses two key metrics: (a) hospitalizations which is a measure of the severity of the illness and (b) wastewater analysis which purportedly measures prevalence.

I say “purportedly” in the light of this observation from Public Health Ontario:

“Wastewater surveillance for COVID-19, when combined with corresponding clinical testing and epidemiology data, may have potential for tracking or anticipating COVID-19 disease trends but is not yet recommended as a means to estimate prevalence. It is a rapidly evolving area of research and operationalization, and as an adjunct to clinical testing for assessing infection rates in a community”. (My underlining)

The Region’s website tells us that wastewater analysis comes from two catchment areas which, together, do not cover the entire Region. We are not told the size of the catchment area.

However, I must assume it is possible to extrapolate the findings across the region. Otherwise, what’s the point? 

How widespread is the virus?

The Toronto Star pulls together the latest data on Covid deaths, hospitalizations and vaccinations with the following caveat:

“On June 16, the Ontario Government halted daily COVID-19 data reporting, moving to weekly reports… Case counts are not included here. Reduced testing this year means that the number of cases shown is no longer an accurate reflection of how widespread the virus is.”

That hits the nail on the head.

There is probably a lot more Covid out there than we care to admit.

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See also Newmarket Today, 30 July 2022

Update on 1 August 2022: from Nature: How long is Covid infectious?

Update on 2 August 2022: The Globe & Mail editorial: The pandemic isn't over but now we are navigating it in the dark