On the analysis of wastewater for COVID

Vincent J. Curtis

9 Mar 22

RE: Straight poop on COVID surveillance.  Editorial the Hamilton Spectator

When I first read about the proposal to monitor wastewater for COVID virus loading, my experience in business and in analytical chemistry told me to be skeptical.  Straightaway, it was obvious that somebody had their hand out.  Grant money was required to develop the analytical technique, and then more money would have to be paid to get the analyses done once the technique was developed.  Nice business, if you can get it.

But even if you could measure accurately the viral load in wastewater, so what?  What can you usefully relate that measurement to?  There’s many a slip betwixt lip and cup.  It was argued that rising viral loads would forecast rising case numbers.  That very thing has been argued the last two weeks.  But what have we actually seen?

If rising viral load in wastewater is analytically (or quantitatively) related to incipient case rise, then the difference in time can’t be more than five to seven days, given the course of the infection.  But for the last two weeks, wastewater numbers in Ontario have been forecasting rising case numbers, which hasn’t occurred.  In fact, case numbers continue to drop.  The link between wastewater number and case number is too tenuous to be useful, it turns out, however plausible the dialectal argument in the proposal seemed.

The relationship between viral load in wastewater and future case number is too weak to be useful.  So, why spend the money?

If it costs him nothing, then the bureaucrat will continue piling up useless data points.  But try to take it out of his pay, and he’ll make damned sure any data he’s paying for himself is very helpful.

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