The university is conducting surveillance testing on undergraduates students on the Danforth Campus.
We (Infectious Disease, Occupational Health, and Medical School Leadership) have and continue to discuss the value of surveillance testing. We recognize that there are widespread misunderstandings of its utility. The purpose of such testing is primarily to monitor the prevalence of disease in a high risk population (not in individuals).
Routine surveillance testing of asymptomatic undergraduate students is part of our institutional testing strategy because their more communal living and potentially lower compliance with public health measures, such masking and distancing, makes them the highest risk population for large clusters of transmission. The intent of the surveillance testing is to serve as an early warning signal. Thus far, it has been of limited benefit. This is because, even in high risk populations during periods of high community transmission, the rate of positivity rarely even reaches 1% and on Danforth we have never exceeded 0.6%.
While a positive test in an asymptomatic individual can be helpful for the initiation of isolation and contact tracing, we have actually seen no transmission in classroom or lab settings on the Danforth campus when everybody is masked, even when a student tested positive. As one might expect, these individuals generally appear to have lower viral loads and are thought to be less likely to spread disease.
In addition, there can be false positives resulting in inappropriate isolation and quarantine of truly uninfected individuals. Importantly, a negative test has very limited value to you as an individual. It reflects a point in time – the shedding of virus on that day and for approximately 18-24 hours from the time of taking the sample. By the time the test result comes back, the situation could be quite different.
There are false negative results attached to asymptomatic testing as well. We have seen both of these scenarios play out in the White House (X3) and in the NFL where daily testing is performed. At least in part, that appears to be due to a natural relaxation in fastidious attention to the effective public health measures we know work when someone receives a negative test. We have seen some anecdotal evidence confirming relaxation of masking and physical distancing following a negative test result on the Danforth campus.
The university is continuously monitoring the data to determine if this strategy needs to change.