COVID-19 Case Investigation and Contact Tracing Efforts from Health Departments - United States, June 25-July 24, 2020

Abstract

Case investigation and contact tracing are core public health tools used to interrupt transmission of pathogens, including SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19); timeliness is critical to effectiveness (1,2). In May 2020, CDC funded* 64 state, local, and territorial health departments^† to support COVID-19 response activities. As part of the monitoring process, case investigation and contact tracing metrics for June 25-July 24, 2020, were submitted to CDC by 62 health departments. Descriptive analyses of case investigation and contact tracing load, timeliness, and yield (i.e., the number of contacts elicited divided by the number of patients prioritized for interview) were performed. A median of 57% of patients were interviewed within 24 hours of report of the case to a health department (interquartile range [IQR] = 27%-82%); a median of 1.15 contacts were identified per patient prioritized for interview^§ (IQR = 0.62-1.76), and a median of 55% of contacts were notified within 24 hours of identification by a patient (IQR = 32%-79%). With higher caseloads, the percentage of patients interviewed within 24 hours of case report was lower (Spearman coefficient = -0.68), and the number of contacts identified per patient prioritized for interview also decreased (Spearman coefficient = -0.60). The capacity to conduct timely contact tracing varied among health departments, largely driven by investigators' caseloads. Incomplete identification of contacts affects the ability to reduce transmission of SARS-CoV-2. Enhanced staffing capacity and ability and improved community engagement could lead to more timely interviews and identification of more contacts.

FIGURE 1

Association between COVID-19 caseload per health department investigator and timeliness of case interviews — 49 health departments, United States, June 25–July 24, 2020 Abbreviation: COVID-19 = coronavirus disease 2019. * The trendline represents the inverse correlation between the average caseload per case investigator and the timeliness of case investigations among 49 health departments.

FIGURE 2

Association between the COVID-19 caseload per health department investigator and number of close contacts identified per case prioritized for interview — 52 health departments, United States, June 25–July 24, 2020 Abbreviation: COVID-19 = coronavirus disease 2019. * The trendline represents the inverse correlation between the average caseload per case investigator and the number of contacts elicited per patient prioritized for interview among 52 health departments.