Thread by @GreaterfoolVan

🧵 BC PH modelling report on Jan 14 said "Virus concentration in wastewater peaked in first week of January and correlates with COVID-19 case counts across FHA and VCH".
"infections are likely to have reached their peak"
news.gov.bc.ca/files/14.01.22… (1/n)

Also "BC's case trajectory so far is consistent with that observed in other jurisdictions.." (2/n)

But with much reduced PCR testing starting Dec 23 (Vancouver) & Dec 30 (Fraser Health), and very high % positivity (40%+), the reported case counts do Not reflect the current situation. (Rapid tests are not reported)

https://twitter.com/GreaterfoolVan/status/1482565422167695360

(3/n)

Wastewater Covid-19 virus concentration in Greater Vancouver went UP 8x-19x between Dec 20 - Jan 5, while officially reported cases Dropped during the same time frame (due to reduced testing)

https://twitter.com/GreaterfoolVan/status/1481373045193326598

(4/n)

% of public-funded tests testing positive in Greater Vancouver increased from 20%'s to 40%'s from Dec 20 to Jan 10, reflecting significant under-testing.

https://twitter.com/GreaterfoolVan/status/1481077305502011397

(5/n)

Also, by limiting PCR to > 65, HCW, living in group settings, unvaccinated, or told to be tested, the reported results only reflect a small group of population. (We can see older population getting over-represented starting late-Dec when RAT replaced PCR). h/t @vb_jens (6/n)

Re: Wastewater Covid-19 virus measurement, it was pioneering work by collaboration of MetroVan, UBC, BCCDC making wastewater info available in 2021.
There was however missing data during Dec 20-Jan 5 due to holidays. (7/n)
metrovancouver.org/services/liqui…

Backgrounder: Wastewater Covid conc. can be diluted by rainfall/snowmelt, esp if there are areas with combined sewer system, or problems of inflow (rain water seeping into broken pipes) and infiltration (ground water penetrating into broken pipes) burnaby.ca/services-and-p… (8/n)

Some jurisdictions correct for the effect of rainfall or dilution by using ways to "normalize" the data.
There is information that currently the BC wastewater does not show normalized data, thus does not correct for factors like rainfall/snowmelt. 613covid.ca/wastewater/ (9/n)

Greater Vancouver experienced significant snowmelt and rain Jan 5-7. (10/n)

News reports of "Excess rainwater in sewer system" with "5 to 10 times the sewage volume, equivalent of 20,000 homes flushing their toilets" (Coquitlam)
burnaby.ca/services-and-p… (11/n)

BCCDC: "recent heavy snowmelt runoff and rain in Metro Vancouver may affect results in unpredictable ways." (12/n)

I believe it is very likely that the wastewater sample during Jan 5-7 may have been under-estimated due to dilution. Another 1-2 weeks of data, normalized for precipitation, should give PH a better picture. (13/n)
#Covid19BC

*Correct link to the Coquitlam sewer story (14/n)
burnabynow.com/local-news/tax…

Going back to the top, BC's current "case trajectory" is Severely underestimated and should not be used to compare to other jurisdictions.
I also do not think BC has reached the "peak of infections" yet. Hospitalizations will lag by another 1-2 weeks. ∼end