The latest update from the Metropolitan Council shows a decrease in the amount of SARS-CoV-2 detected in wastewater flowing through the seven-county Twin Cities metro.
The amount of coronavirus (SARS-CoV-2) detected in wastewater can serve as a predictor for a rise or fall in infections, as new cases tend to lag wastewater detection trends by about 6-8 days.
The virus is tracked in wastewater by copies of viral RNA per milliliter. And the number of copies per milliliter tends to correspond with the number of cases in the metro per 100,000 people. You can see the corresponding trends in the line graph below.
The Met Council was tracking 232 copies per milliliter on Dec. 18 before it shot up to a pandemic-high 1,047 on Jan. 6. But the latest report issued Monday shows that copies per milliliter have dropped 35% to 679, as of Jan. 12.
If the wastewater detection decreasing isn't a fluke, one could logically assume that the number of cases – at least in the Twin Cities metro area – will soon begin to decline.
The Met Council also tracks which variant of the coronavirus is flowing through sewage. As you can see in this chart, the delta variant (blue) accounted for 100% of all wastewater samples for months, only to rapidly be replaced by the extremely transmissible omicron variant. As of Jan. 13, wastewater samples were 93% omicron and just 3% delta.
If the wastewater samples are accurate in predicting the rise and fall of COVID-19 cases, then the Twin Cities area and perhaps all of Minnesota could soon experience a rapid decline in cases.
For example, in the Boston metro area, the viral load in wastewater skyrocketed around the holidays before dropping just as rapidly, according to the Boston Herald. Health officials there are "cautiously optimistic" they are headed for a sharp decline in cases, followed by a drop in hospitalizations a few weeks later.