Lots of good points here! Viral loads and variants are important to keep in mind when interpreting wastewater data. That said, our current best guess is that the rising SARS-CoV-2 concentration in Boston wastewater reflects a real increase in cases. Delta has higher nasal shedding than other variants, but not necessarily higher fecal shedding--the ratio of wastewater concentrations to clinical cases seems pretty constant in our data over time (see our blog post on this topic here: https://biobotanalytics.medium.com/mass-vaccination-delta-an...) We know much less about omicron, but it's probably still only a small minority of cases. We're currently sequencing samples of Boston wastewater, so we'll know more about omicron levels in wastewater very soon!