Characteristics and Outcomes of Contacts of COVID-19 Patients Monitored Using an Automated Symptom Monitoring Tool — Maine, May–June 2020

Anna Krueger, MS; Jayleen K. L. Gunn, PhD; Joanna Watson, DPhil; Andrew E. Smith, ScD; Rebecca Lincoln, ScD; Sara L. Huston, PhD; Emilio Dirlikov, PhD; Sara Robinson, MPH


Morbidity and Mortality Weekly Report. 2020;69(31):1026-1030. 

In This Article

Abstract and Introduction


SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19), is spread from person to person.[1–3] Quarantine of exposed persons (contacts) for 14 days following their exposure reduces transmission.[4–7] Contact tracing provides an opportunity to identify contacts, inform them of quarantine recommendations, and monitor their symptoms to promptly identify secondary COVID-19 cases.[7,8] On March 12, 2020, Maine Center for Disease Control and Prevention (Maine CDC) identified the first case of COVID-19 in the state. Because of resource constraints, including staffing, Maine CDC could not consistently monitor contacts, and automated technological solutions for monitoring contacts were explored. On May 14, 2020, Maine CDC began enrolling contacts of patients with reported COVID-19 into Sara Alert (MITRE Corporation, 2020),* an automated, web-based, symptom monitoring tool. After initial communication with Maine CDC staff members, enrolled contacts automatically received daily symptom questionnaires via their choice of e-mailed weblink, text message, texted weblink, or telephone call until completion of their quarantine. Epidemiologic investigations were conducted for enrollees who reported symptoms or received a positive SARS-CoV-2 test result. During May 14–June 26, Maine CDC enrolled 1,622 contacts of 614 COVID-19 patients; 190 (11.7%) eventually developed COVID-19, highlighting the importance of identifying, quarantining, and monitoring contacts of COVID-19 patients to limit spread. In Maine, symptom monitoring was not feasible without the use of an automated symptom monitoring tool. Using a tool that permitted enrollees to specify a method of symptom monitoring was well received, because the majority of persons monitored (96.4%) agreed to report using this system.

Public health investigators interviewed persons with COVID-19 upon report of the case to Maine CDC to collect information about their contacts, including date of last exposure. Contacts were defined as persons who were within 6 feet of an infectious person for ≥15 minutes (≥30 minutes before May 29). Data were stored in the National Electronic Disease Surveillance Base System (NBS)§ and sent to Maine CDC's contact tracing team within 24 hours, along with contact data reported to Maine CDC by other jurisdictions and CDC's Division of Global Migration and Quarantine. The contact tracing team telephoned contacts to provide quarantine recommendations, enroll them in Sara Alert, and instruct them to report symptoms daily via the Sara Alert questionnaire for the remainder of their quarantine. If contacts refused automated monitoring or could not be enrolled because of language barriers, they would be monitored using direct monitoring. Per the Council of State and Territorial Epidemiologists' case definition,** monitored signs and symptoms included cough, difficulty breathing, fever, chills, shaking with chills (rigors), muscle pain, headache, sore throat, and new loss of taste or smell. The contact tracing team attempted to directly monitor contacts who refused or were unable to be enrolled. Maine CDC staff members conducted case investigations for all enrollees who sought SARS-CoV-2 molecular testing and had a positive result (confirmed cases) irrespective of symptoms and those who did not have molecular testing but reported symptoms (probable cases). Staff members attempted to call or text enrollees who did not respond to the questionnaire within 24 hours. Enrollees who did not report symptoms during their quarantine period were automatically released from quarantine by a Sara Alert–issued notice. Data for contacts enrolled during May 14–June 26, 2020, were extracted from Sara Alert. Enrollee demographic characteristics and Sara Alert program preferences, selected by enrollees at the time of enrollment, were analyzed, and the number of persons enrolled per household were calculated based on self-reported address.

All persons enrolled in Sara Alert during the study period were matched to NBS records using date of birth and the first initial of their first and last names. NBS data were extracted on July 10 to allow contacts enrolled by June 26 to complete 14 days of quarantine. Data extracted from NBS included case status (confirmed or probable), hospitalization status, and outcome, including death. For most analyses, confirmed and probable cases were combined. SAS (version 9.3; SAS Institute) was used to conduct analyses. This activity was determined to meet the requirements of public health surveillance as defined in 45 CFR 46.102(l)(2).

During May 14–June 26, 2020, Maine enrolled 1,622 contacts (enrollees) of 614 COVID-19 patients in Sara Alert. The average number of enrollees per index patient was 2.9 (range = 0–31). Among enrollees, median age was 29 years (range = 0–93 years); 766 (50.3%) were female (Table 1). Race data were available for 1,240 (76.4%) enrollees, 732 (59.0%) of whom identified as white and 486 (39.2%) as black/African American. Ethnicity data were available for 1,020 (62.9%) enrollees, 42 (4.1%) of whom identified as Hispanic/Latino. Primary language was documented for 1,230 (75.8%) enrollees; 985 (80.1%) primarily spoke English, 86 (7.0%) French, and 81 (6.6%) Somali.

Overall, 475 (29.3%) of 1,622 enrollees were enrolled within 2 days of their last exposure to the patient (Table 2), including 153 (9.5%) enrolled the day of their last exposure, likely indicating ongoing exposure. Among enrollees, 1,564 (96.4%) agreed to be monitored using the automated symptom monitoring, whereas 58 (3.6%) required direct monitoring. Enrollees using automated symptom monitoring preferred text message (976; 60.2%), followed by texted weblink (342; 21.1%), telephone call (127; 7.8%), and e-mailed weblink (119; 7.3%). Most enrollees (870; 59.0%) preferred an evening contact time.

Among all enrollees, 231 (14.2%) reported symptoms or had a positive test result. Among these enrollees, 41 (17.7%) were determined not to have COVID-19, including 24 who received negative test results and 17 whose symptoms did not meet those specified by the case definition; these 41 enrollees were reenrolled in Sara Alert for the remainder of their quarantine. Among all enrollees, 190 (11.7%) met the COVID-19 case definition. Among these 190 persons, 127 (66.8%) were confirmed to have COVID-19, and 63 (33.2%) were considered to have probable cases (Table 3). Among all persons with probable and confirmed cases, median age was 32 years (range = 0–93 years); 99 (52.1%) were female. Race data were available for 186 (97.9%) patients, among whom 98 (52.7%) identified as white and 81 (43.5%) as black/African American. Ethnicity was available for 182 (95.8%) patients, six (3.3%) of whom identified as Hispanic/Latino. Exposure was self-reported for 165 (86.8%) patients; household exposure was most common (112; 67.9%). COVID-19 symptoms were reported for 136 (74.3%) patients. Four (2.1%) patients were hospitalized, and one (0.5%) died. During May 14–July 10, Maine reported 1,869 total COVID-19 cases††; thus, approximately 10% of Maine's COVID-19 patients were identified among Sara Alert enrollees.

For symptomatic persons, this was defined as 2 days before symptom onset to at least 10 days following symptom onset. For asymptomatic persons, this was defined as 2 days before collection of a specimen that resulted in a positive test to 10 days following specimen collection date.
§Maine's National Electronic Disease Surveillance Base System is a local installation and configuration of CDC's National Electronic Disease Surveillance Base System.