Some interesting and good news out of the University of Arizona. Scientists’ fascination with sewage stops community spread:
Some big news out of the University of Arizona (@uarizona):
UA scientists & staff found a coronavirus outbreak on campus *before it happened* — and seem to have snuffed it out.
How in the world do you do that?
You use wastewater testing.
— (((Charles Fishman))) (@cfishman) August 27, 2020
The short version is that people who are infected with COVID begin to defecate COVID virus traces very quickly after they become infected. This fact plus a very good understanding by the University of Arizona’s staff about their sewage system allowed for the installation of a partial campus disease surveillance and early warning network. Roughly 20 buildings including all occupied dorms’ outflow pipers are monitored. Before students came on campus, all of these dorms had no COVID in their outflow.
Earlier this week, one dorm had a detected spike in COVID virus traces in the sewage. This is a surveillance signal. It was a signal that was good enough to say “PROBLEM IN HOUSE X”.
The University of Arizona had an action plan; they tested every dorm resident dorm with rapid turnaround tests. 2 out of 300+ people returned a presumed positive test. Those two folks will have a PCR diagnostic test for confirmation. While the confirmation results are being processed, the two presumed positive individuals are isolated and put under medical surveillance. Follow-on testing may be used to confirm that close contacts are not infected.
This is aggressive and effective community public health where the University of Arizona was able to identify non-symptomatic individuals who are likely to be in their infectious period early enough that the window where the presumed infected individuals could bump into non-infected and susceptible people is very small.
It is a good case example of how the surveillance, test, and isolate cycles can work. Sewage surveillance is a valuable tool for public health epidemiologists for COVID and for many other infectious diseases that are often minimally symptomatic. It gives a strong enough signal that should trigger a targeted, localized and effective response. Other surveillance strategies can also perform that function. Routine, recurring, low cost and modestly sensitive testing with extremely rapid turnaround is a more distributed strategy which should allow for the smothering of outbreaks at the individual and micro-cluster level of correlated risk (families, roommmates etc) instead of broad clusters (entire dorms, apartment buildings, most of a workplace etc).