Isolation Precautions and COVID-19: How Long is Enough?

The coronavirus 2019 (COVID-19) pandemic isn’t likely to be ending any time soon. With cases surging across many states in the US, and delays in testing, there is an increasing focus on sustainable response and the need to get a handle on the pandemic.

An important element to this is the use of isolation precautions in healthcare. Isolation of sick and infectious patients is a critical piece to breaking the chain of transmission. One piece though, for any novel disease, is the duration of isolation precautions. The Centers for Disease Control and Prevention (CDC) guidelines have been 10 days since symptoms began (or since the positive test if asymptomatic) and 72 hours without a fever (and the use of fever reducers) with symptoms resolving.

On July 17, the CDC released new guidance based off new research and findings. One piece to this focuses on isolation precautions—for most people they can be discontinued 10 days after symptom onset and resolution of fever for at least 24 hours (without the use of fever reducers) and improvement of other symptoms. For those with more severe illness, it is likely that they produce replicant-competent virus beyond that 10 days which could mean isolation should be extended for up to 20 days after symptom onset.

These updates come just a few short weeks after another study within the American Journal of Infection Control. Researchers worked to evaluate strategies for determining when it is safe to discontinue isolation precautions for COVID-19 patients. This analysis reviewed data from 100 patients in the Mayo Clinic Florida’s COVID Virtual Clinic. Evaluating length of time from detectable to undetectable results, length of time from onset of symptoms to undetectable result, and length of time from resolution of fever to detectable result.

The authors noted that “Analysis of the first 100 patients revealed that 87% met CDC criteria for the symptom-based strategy for release from isolation (fever-free greater than 72 hours, improved symptoms, and 10 days from first symptoms). 53% (N=31) of eligible patients continued to have detectable results and require repeat testing. Of eligible repeat testers, only 48.75% (N=39) had undetectable results. The mean and median time for onset of symptoms in these patients to undetectable testing was 21.5 and 20.5 days, respectively.”

The mean time from first detected result to undetectable result was 14.89 days. Interestingly, of those 39 patients who were retested, 33% reported that their fever resolving as the key indicator for symptom resolution. Overall, this study sheds light on the ongoing discussion regarding isolation precautions. With the new CDC guidance, it does underscore the implications for severe disease, which was not accounted for in this study.

Another key piece is that detectable viral RNA does not equate to infectious viral RNA, meaning that was is shed may not be viable material to cause infection. With these discussions, it will be important to differentiate detection that relies on highly sensitive tests that might yield positive results based off unviable versus infectious viral particles. Currently, the new CDC guidelines mirror this sentiment of longer isolation for those with severe disease but do address the 10-day rule for most people with mild illness or no symptoms.