Characteristics and Timing of Initial Virus Shedding in Severe Acute Respiratory Syndrome Coronavirus 2, Utah, USA

Nathaniel M. Lewis; Lindsey M. Duca; Perrine Marcenac; Elizabeth A. Dietrich; Christopher J. Gregory; Victoria L. Fields; Michelle M. Banks; Jared R. Rispens; Aron Hall; Jennifer L. Harcourt; Azaibi Tamin; Sarah Willardson; Tair Kiphibane; Kimberly Christensen; Angela C. Dunn; Jacqueline E. Tate; Scott Nabity; Almea M. Matanock; Hannah L. Kirking


Emerging Infectious Diseases. 2021;27(2):352-359. 

In This Article

Abstract and Introduction


Virus shedding in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can occur before onset of symptoms; less is known about symptom progression or infectiousness associated with initiation of viral shedding. We investigated household transmission in 5 households with daily specimen collection for 5 consecutive days starting a median of 4 days after symptom onset in index patients. Seven contacts across 2 households implementing no precautionary measures were infected. Of these 7, 2 tested positive for SARS-CoV-2 by reverse transcription PCR on day 3 of 5. Both had mild, nonspecific symptoms for 1–3 days preceding the first positive test. SARS-CoV-2 was cultured from the fourth-day specimen in 1 patient and from the fourth- and fifth-day specimens in the other. We also describe infection control measures taken in the households that had no transmission. Persons exposed to SARS-CoV-2 should self-isolate, including from household contacts, wear a mask, practice hand hygiene, and seek testing promptly.


The coronavirus disease (COVID-19) outbreak first recognized in Wuhan, China, in December 2019 is now a global pandemic.[1] Serial intervals for transmission have been estimated,[2,3] and presymptomatic transmission from confirmed case-patients to others has been documented.[4–8] In addition, studies suggest that virus shedding can begin before the onset of symptoms[7,8] and extend beyond the resolution of symptoms.[9] However, data on the initiation and progression of viral shedding in relation to symptom onset and infectiousness are limited. Intensive early monitoring of household members through serial (i.e., daily) collection of a respiratory tract specimen for testing by real-time reverse transcription PCR (rRT-PCR), which could clarify the characteristics of initial viral shedding, has rarely been implemented, although serial self-collection of nasal and saliva samples was used in a recent study.[10] To examine the transmission dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and guide public health recommendations, we describe initial detection and progression of SARS-CoV-2 viral shedding, as indicated by rRT-PCR positivity for SARS-CoV-2 and cycle threshold (Ct) values, in relation to exposure to an index patient, symptom onset and duration, and transmission to household contacts who underwent intensive early monitoring with viral cultures.