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

Our take —

In the U.S. state of Maine, the overwhelming majority of COVID-19 contacts who participated in symptom monitoring opted to do so with an automated system using text messages or the web. Contacts who did not participate were not enumerated, making it difficult to draw broad conclusions about the effectiveness of this tool. Among all participating contacts, 12% developed COVID-19 (representing 10% of all cases in Maine during the study period), 68% of whom had household exposure; these findings are in line with estimates from contact tracing studies from South Korea and elsewhere.

Study design

Prospective Cohort, Other

Study population and setting

This study reported on 1,622 contacts (median age 29 years, 50% female) of 614 COVID-19 patients in the US state of Maine who were enrolled in an automated, web-based symptom monitoring program. Contacts were defined as anyone who was within 6 feet of an infectious contact (from 2 days before symptom onset to 10 days after symptom onset; for asymptomatic cases, the date of a positive test was used instead of symptom onset) for 15 minutes or longer. Contacts were instructed to report symptoms daily via an online questionnaire for the duration of their recommended 14-day quarantine; symptoms included cough, difficulty breathing, fever, chills, shaking with chills, muscle pain, headache, sore throat, and new loss of taste or smell. If contacts preferred not to report symptoms with the automated system, they were directly monitored by contact tracing investigators. Demographic information and symptom monitoring preferences were collected at enrollment. Case investigations were undertaken for any contact with a positive SARS-CoV-2 test result or with symptoms absent testing.

Summary of Main Findings

The vast majority (96%) of enrollees chose automated symptom monitoring over direct monitoring by public health investigators. Of those opting for automated monitoring, 60% preferred text message delivery, 21% preferred texted web link, 8% preferred telephone, and 8% preferred emailed web link. Twenty-nine percent of participants were enrolled within two days of their last contact with the index case. There were an average of 2.9 contacts per index case enrolled, and 29% of participating households had more than one enrollee. Among enrolled contacts with available data (76% for race, 63% for ethnicity), 59% were white and 39% were Black, while 4% identified as Latino or Hispanic. The primary language spoken by participants was reported as English by 80% of contacts, French by 7%, and Somali by 7%. Symptoms or a positive SARS-CoV-2 test result were reported by 231 (14%) enrollees, 190 (12%) of whom met the case definition for COVID-19. Of these 190, 127 had confirmed COVID-19, while the remaining 63 were considered probable cases. Probable and confirmed cases represented 10% of all reported cases (n=1869) in Maine during the study period. Of the 165 cases of COVID-19 among enrollees with data on source of exposure to the index case, 68% had household exposure, 18% had community exposure, and 16% had health care exposure. Four patients were hospitalized, and one died.

Study Strengths

Although the participation rate among all contacts is unknown, those who did participate provided useful data on preferences and outcomes. A sizable proportion of COVID-19 cases in Maine (10%) were identified through contact tracing and assessed via the automated monitoring program during the study period.


Data were not available on the total number of contacts reported by index cases. Therefore, the participation rate could not be calculated, and it is not possible to draw strong conclusions about the acceptability of automated symptom monitoring. Additionally, if participation was low among contacts, the preferences, reporting behavior, and outcomes among this group of contacts may not be representative of contacts in Maine. Losses to follow-up may be under-reported, as they were not distinguished from those released from quarantine. Similarly, COVID-19 cases were likely under-reported, since SARS-CoV-2 testing was not required or administered to all contacts.

Value added

This study adds valuable (if incomplete) data on contact tracing preferences and outcomes, as few such results from the United States have been published to date.

This review was posted on: 18 August 2020