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

Abstract

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.

Keywords: COVID-19; SARS virus; SARS-CoV-2; coronavirus disease; respiratory infections; reverse transcription PCR; severe acute respiratory syndrome coronavirus 2; virus shedding; viruses; zoonoses.

Figure 1

Results of rRT-PCR for SARS-CoV-2 and symptom onset among index case-patients, SARS-CoV-2–positive household contacts, and SARS-CoV-2–negative household contacts in study of initial virus shedding in SARS-CoV-2, Utah, USA, April–May 2020. The timelines of symptom onset and testing dates preceding and during the 15-day study period are ordered by individual households (HH-01–HH-05). Sex and age (in parentheses) are listed to the left. Symptom onset date is only included for household members who tested positive at any time during the study period or for whom onset of symptoms consistent with coronavirus disease prompted an interim visit from investigators. HH-05 opted out of day 14 nasopharyngeal specimen collection. C_t, cycle threshold; HH, household; rRT-PCR, real-time reverse transcription PCR; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Figure 2

Symptom timing, symptom type, cycle threshold values, and viral culture results among household contacts positive for SARS-CoV-2 by rRT-PCR in study of initial virus shedding in SARS-CoV-2, Utah, USA, April–May 2020. The symptom onset and progression of 7 SARS-CoV-2–positive household contacts in households 2 and 5 (HH-02 and HH-05), who tested positive by real-time reverse transcription PCR, are detailed from first symptom onset to the end of the daily swabbing period (days 0–4). Fading bars indicate symptoms persisting after day 5. CSTE, Council of State and Territorial Epidemiologists; C_t, cycle threshold; rRT-PCR, real-time reverse transcription PCR; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.