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Identification and Monitoring of International Travelers During the Initial Phase of an Outbreak of COVID-19 – California, February 3-March 17, 2020

Our take —

During the first seven weeks of a symptom monitoring program for inbound travelers to the United States from China and Iran, the California Department of Health reviewed and forwarded 12,061 traveler records, many containing errors or omissions, to 51 health jurisdictions, generating 1,694 additional person-hours of labor and only three matches to confirmed COVID-19 cases in California. Traveler symptom monitoring is a resource- and time-intensive intervention which, independent of other mitigation activities, may be insufficient for containing COVID-19 transmission in community settings.

Study design


Study population and setting

The study reviews the implementation of California Department of Health’s (CDPH) symptom monitoring program for travelers arriving from China and Iran to 51 local health jurisdictions between February 3 and March 17, 2020. On February 3, 2020, the United States directed all inbound flights from China to 11 airports for streamlined COVID-19 entry screening, whereby travelers’ information was collected and distributed to state health departments in the jurisdiction of the travelers’ final destination. Guidelines were expanded on March 5, 2020 to include individuals with recent (14 days) travel to Iran. Customs and Border Protection agents implemented secondary screening of inbound travelers, assessed travelers for signs and symptoms of COVID-19, and directed all travelers to quarantine and/or self-monitor (based on CDC risk assessment criteria) for two weeks following their last potential exposure to COVID-19. Where possible, local health jurisdictions were directed to contact travelers residing in their jurisdictions and collect daily reports on developing signs or symptoms, using information transmitted from Customs and Border Protection to health departments via CDC’s Epi-X system. Traveler records transmitted and local health jurisdiction person-hours implementing symptom monitoring between February 3 and March 17, 2020 were aggregated for descriptive analysis.

Summary of Main Findings

Of the 2,266 Epi-X notifications processed by CDPH (corresponding to 12,061 individual travelers) between February 3 and March 17, 2020, 13% had identifiable errors: 75% contained incorrect U.S. telephone numbers, 40% were duplicates, and 32% were untraceable or resided outside California. Of the 11,574 travelers for whom records were distributed by CDPH to 51 local health jurisdictions, three had a confirmed COVID-19 diagnosis in California. 1,694 total person-hours of CDPH labor, 34% of which were outside ordinary business hours, were attributed to reviewing and disseminating Epi-X notifications to local health jurisdictions.

Study Strengths

The study descriptively summarizes input and process indicators (i.e., number of traveler records disseminated and person-hours of labor) to appraise the feasibility of a symptom monitoring program.


The study did not aggregate person-hours of implementation labor from local health jurisdictions or compare these estimated labor inputs with labor availability (i.e., number of staff available in each jurisdiction to conduct traveler symptom monitoring). Other relevant process level indicators, like program-associated costs and traveler lost-to-follow-up rates during symptom monitoring, were also not enumerated.

Value added

This is among the first studies to descriptively assess the feasibility of implementing a symptom monitoring program in a U.S. destination (i.e., California) with high inbound traveler volume from COVID-19-impacted origins.