Infectious Period of Severe Acute Respiratory Syndrome Coronavirus 2 in 17 Nursing Home Residents-Arkansas, June-August 2020

Abstract

Background: To estimate the infectious period of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in older adults with underlying conditions, we assessed duration of coronavirus disease 2019 (COVID-19) symptoms, reverse-transcription polymerase chain reaction (RT-PCR) positivity, and culture positivity among nursing home residents.

Methods: We enrolled residents within 15 days of their first positive SARS-CoV-2 test (diagnosis) at an Arkansas facility from July 7 to 15, 2020 and instead them for 42 days. Every 3 days for 21 days and then weekly, we assessed COVID-19 symptoms, collected specimens (oropharyngeal, anterior nares, and saliva), and reviewed medical charts. Blood for serology was collected on days 0, 6, 12, 21, and 42. Infectivity was defined by positive culture. Duration of culture positivity was compared with duration of COVID-19 symptoms and RT-PCR positivity. Data were summarized using measures of central tendency, frequencies, and proportions.

Results: We enrolled 17 of 39 (44%) eligible residents. Median participant age was 82 years (range, 58-97 years). All had ≥3 underlying conditions. Median duration of RT-PCR positivity was 22 days (interquartile range [IQR], 8-31 days) from diagnosis; median duration of symptoms was 42 days (IQR, 28-49 days). Of 9 (53%) participants with any culture-positive specimens, 1 (11%) severely immunocompromised participant remained culture-positive 19 days from diagnosis; 8 of 9 (89%) were culture-positive ≤8 days from diagnosis. Seroconversion occurred in 12 of 12 (100%) surviving participants with ≥1 blood specimen; all participants were culture-negative before seroconversion.

Conclusions: Duration of infectivity was considerably shorter than duration of symptoms and RT-PCR positivity. Severe immunocompromise may prolong SARS-CoV-2 infectivity. Seroconversion indicated noninfectivity in this cohort.

Keywords: COVID-19; RT-PCR; SARS-CoV-2; infectivity; nursing homes.

Figure 1.

Timeline showing number of nursing home residents (N = 95) newly testing positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after serial point-prevalence surveys, notable events, and period of enrollment at the nursing home—Arkansas, June 9–July 15, 2020. HCP, healthcare personnel.

Figure 2.

Timeline of visits and activities conducted at each visit, including questionnaire administration and specimen collection. COVID-19, coronavirus disease 2019; PCR, polymerase chain reaction.

Figure 3.

Participant enrollment among all residents (N = 95) at the nursing home—Arkansas, July 7–15, 2020. SARS-CoV-2, severe acute respiratory syndrome coronavirus 2

Figure 4.

Period of COVID-19 symptoms (A) and detection of SARS-CoV-2 RNA by RT-PCR, viral culture, and seroconversion (B) among participants (N = 17) at nursing home — Arkansas, July–August 2020. Notes: (1) RT-PCR-positive result at day 0 represents initial diagnosis; (2) Composite RT-PCR results are determined from attempted collection of oropharyngeal, anterior nares, and saliva specimens at each visit. Due to challenges with specimen collection, transport, and processing, RT-PCR results for each specimen type were not always available for each visit. (3) Seroconversion was determined by a signal threshold >1 at the 1:100 dilution. Figure 4B notes: †Participants A and N could not be phlebotomized; ∞Participants B, D, and K all had blood collections at enrollment, but subsequent collections were missed due to refusal, hospitalization, or death.

Figure 5.

Viral culture results of reverse-transcription polymerase chain reaction (RT-PCR)-positive oropharyngeal and anterior nares specimens by cycle threshold (Ct) value and days since first RT-PCR-positive result among participants (N = 17) at nursing home—Arkansas, July–August 2020. *The lowest Ct value for N1 is displayed from a composite of oropharyngeal and anterior nares specimens for each participant. --- Indicates a Ct value of 29, above which replication-competent virus could not be cultured.