Lessons Learned from CDC's Global COVID-19 Early Warning and Response Surveillance System

Abstract

Early warning and response surveillance (EWARS) systems were widely used during the early COVID-19 response. Evaluating the effectiveness of EWARS systems is critical to ensuring global health security. We describe the Centers for Disease Control and Prevention (CDC) global COVID-19 EWARS (CDC EWARS) system and the resources CDC used to gather, manage, and analyze publicly available data during the prepandemic period. We evaluated data quality and validity by measuring reporting completeness and compared these with data from Johns Hopkins University, the European Centre for Disease Prevention and Control, and indicator-based data from the World Health Organization. CDC EWARS was integral in guiding CDC's early COVID-19 response but was labor-intensive and became less informative as case-level data decreased and the pandemic evolved. However, CDC EWARS data were similar to those reported by other organizations, confirming the validity of each system and suggesting collaboration could improve EWARS systems during future pandemics.

Keywords: COVID-19; Centers for Disease Control and Prevention; Early Warning and Response Surveillance; SARS; SARS-CoV-2; United States; World Health Organization; coronavirus; coronavirus disease; public health surveillance; respiratory infections; severe acute respiratory syndrome coronavirus 2; validation study; viruses; zoonoses.

Figure 1

Overview of public health surveillance and response functions used in an evaluation of the Centers for Disease Control and Prevention Early Warning and Response Surveillance system. Adapted from the World Health Organization (4). *Conventional human surveillance based on biological confirmation of cases.†Human case data based on syndromic definition. ‡Data and information in relation to human health (e.g., media reports, sick leave, medicine sales, population movement, social unrest, etc.). §Veterinary surveillance (zoonosis), environmental or biological surveillance (e.g., meteorlogical, vector density, water and air quality, etc.).

Figure 2

Work and information flow for CDC EWARS during epidemiologic weeks 3–9, January 20–March 7, 2020. CDC EWARS, US Centers for Disease Control and Prevention global COVID-19 Early Warning and Response Surveillance system; MoH, ministry of health; NPHI, national public health institutions.

Figure 3

Cumulative confirmed COVID-19 cases reported outside of mainland China and the United States by CDC EWARS and other surveillance systems during epidemiologic weeks 3–9, January 20–March 7, 2020. CDC EWARS, US Centers for Disease Control and Prevention global COVID-19 Early Warning and Response Surveillance system; ECDC, European Centers for Disease Control; EW, epidemiologic week; JHU, Johns Hopkins University Center for Systems Science and Engineering; WHO, World Health Organization.

Figure 4

Cumulative reported confirmed COVID-19 deaths and cumulative number of countries reporting confirmed COVID-19 cases for CDC EWARS, JHU, WHO, and ECDC systems during epidemiologic weeks 3–9, January 20–March 7, 2020. WHO death counts were used as CDC EWARS inputs after epidemiologic week 8. Scales for the y-axes differ substantially to provide data on 2 different indicators and are not intended for direct comparisons. CDC EWARS, US Centers for Disease Control and Prevention global COVID-19 Early Warning and Response Surveillance system; ECDC, European Centers for Disease Control; JHU, Johns Hopkins University Center for Systems Science and Engineering; WHO, World Health Organization.

Figure 5

Scatterplot showing differences in individual country COVID-19 cumulative case-counts outside of mainland China and the United States between JHU, WHO, or ECDC systems, and CDC EWARS system during epidemiologic weeks 3–9, January 20–March 7, 2020. A value of zero indicates CDC EWARS and the other system had the same number of weekly cumulative cases for a given country; a negative value means that CDC EWARS reported a higher number of cases; and a positive value means that the other surveillance system reported more cases than CDC EWARS. Differences of >50 cases between CDC EWARS and WHO or ECDC for cumulative country case counts occurred in 6% (18/295) of instances, and between CDC EWARS and JHU in 1% (4/295) of instances. CDC EWARS, US Centers for Disease Control and Prevention global COVID-19 Early Warning and Response Surveillance system; ECDC, European Centers for Disease Control; JHU, Johns Hopkins University Center for Systems Science and Engineering; WHO, World Health Organization.