Modeling the effectiveness of olfactory testing to limit SARS-CoV-2 transmission

Abstract

A central problem in the COVID-19 pandemic is that there is not enough testing to prevent infectious spread of SARS-CoV-2, causing surges and lockdowns with human and economic toll. Molecular tests that detect viral RNAs or antigens will be unable to rise to this challenge unless testing capacity increases by at least an order of magnitude while decreasing turnaround times. Here, we evaluate an alternative strategy based on the monitoring of olfactory dysfunction, a symptom identified in 76-83% of SARS-CoV-2 infections -- including those that are otherwise asymptomatic -- when a standardized olfaction test is used. We model how screening for olfactory dysfunction, with reflexive molecular tests, could be beneficial in reducing community spread of SARS-CoV-2 by varying testing frequency and the prevalence, duration, and onset time of olfactory dysfunction. We find that monitoring olfactory dysfunction could reduce spread via regular screening, and could reduce risk when used at point-of-entry for single-day events. In light of these estimated impacts, and because olfactory tests can be mass produced at low cost and self-administered, we suggest that screening for olfactory dysfunction could be a high impact and cost effective method for broad COVID-19 screening and surveillance.

Higher viral load drives infrequent SARS-CoV-2 transmission between asymptomatic residence hall roommates

“…Second, a notable contribution of this work is to provide evidence that viral levels are positively correlated with the probability of transmission in the context of a high frequency screening program. There has been very little work examining the relationship between viral load and the risk of transmission, although it is a common hypothesis underpinning COVID-19 transmission modeling studies (Larremore et al, 2021, 2020). We observed that students who transmitted SARS-CoV-2 to their roommates had, on average, 6.5-fold higher viral loads than students who did not transmit virus to their roommates (Figure 4).…”

Improved screening of COVID-19 cases through a Bayesian network symptoms model and psychophysical olfactory test

“…It can substantially mitigate disease transmission as patients with no apparent symptoms are less likely to follow public health guidelines compared to symptomatic patients [57]. Several studies have stressed the importance of frequent, mass testing [16, 17], and modeling suggests that frequent screening for olfactory dysfunction could substantially reduce viral spread [58]. Until a substantial proportion of the population is vaccinated, frequent, accessible, routine screening for COVID-19 is critical to isolate infectious individuals and effectively break the chain of viral transmission.…”

“…Some of the cases we classified as false-positives due to negative RT-PCR results could have been true COVID-19 cases. This also underscores the importance of frequent testing for COVID-19 [16, 17, 58].…”

“…Several studies have stressed the importance of frequent, mass testing, with a short sample-to-answer reporting time to limit viral transmission in this epidemic [16, 17, 25, 26]. Furthermore, modeling suggests that frequent screening for olfactory dysfunction could substantially reduce viral spread at a comparatively low cost [27]. However, despite the expectation that an olfactory test would be cost-effective [27], some settings with limited resources may not necessarily afford it financially.…”

“…Modeling studies have shown that effective COVID-19 surveillance should prioritize the frequency of testing, accessibility, and immediate results [16, 25, 26]. Infectious individuals might then be able to isolate and stop onward transmission promptly.This could be achieved, for example, using antigen tests which can have a turnaround time as low as 15 minutes and may cost about USD5-50 per test, or using mass screening for specific high-prevalence symptoms of SARS-CoV-2 infection, such as olfactory dysfunction [27].…”