A glossary of common terms used in the COVID-19 Contact Tracing Playbook

CASE Refers to a person with probable or confirmed COVID-19 infection.

CONFIRMED CASE Meets confirmatory laboratory evidence.


  • Meets clinical criteria AND epidemiologic evidence with no confirmatory laboratory testing performed for COVID-19; or

  • Meets presumptive laboratory evidence AND either clinical criteria OR epidemiologic evidence; or

  • Meets vital records criteria with no confirmatory laboratory testing performed for COVID-19 (Source: CDC)

COVID-19 The name of the disease caused by the novel coronavirus, SARS-CoV-2, and is short for “Coronavirus Disease 2019.” (Source: WHO)

CONTACT or CLOSE CONTACT A person who may be at risk for a contagious disease because of their proximity or exposure to a known case. Exact definition of close contact differs by disease; for COVID-19, CDC defines a close contact as someone who was within 6 feet of an infected person for at least 15 minutes starting from 48 hours before illness onset until the time the patient is isolated. Data are limited to precisely define the “prolonged exposure” to determine “close contact”, however 15 minutes of close exposure can be used as an operational definition for contact investigation. Factors to consider when defining close contact include proximity, the duration of exposure (e.g., longer exposure time likely increases exposure risk), whether the individual has symptoms (e.g., coughing likely increases exposure risk) and whether either the case patient or contact were wearing an N95 respirator (which can efficiently block respiratory secretions from contaminating others and the environment). At this time, differential determination of close contact for those using fabric face coverings is not recommended. (Source: CDC)

CONTAINMENT Preventing the spread of disease in early stages of transmission through measures such as early detection and isolation of cases, and contact tracing and quarantine. (Source: WHO)

EPIDEMIOLOGIST When disease outbreaks or other threats emerge, epidemiologists are on the scene to investigate. Often called “Disease Detectives”, epidemiologists search for the cause of disease, identify people who are at risk, determine how to control or stop the spread or prevent it from happening again. Physicians, veterinarians, scientists, and other health professionals often train to be “Disease Detectives”. (Source: CDC)

HIGH-RISK INDIVIDUALS People at higher risk for severe illness from COVID-19. Based on the current evidence, high-risk individuals include:

  • People 65 years and older

  • People of all ages with underlying medical conditions, particularly if not well controlled, including: people with chronic lung disease or moderate to severe asthma; people who have serious heart conditions; people who are immunocompromised due to causes including cancer treatment, smoking, bone marrow or organ transplantation, immune deficiencies, poorly controlled HIV or AIDS or prolonged use of corticosteroids or other immune weakening medications; people with severe obesity (body mass index [BMI] of 40 or higher); people with diabetes; people with chronic kidney disease undergoing dialysis; and people with liver disease (Source: CDC)

INFECTIOUS PERIOD The onset and duration of viral shedding; not yet known for COVID-19. (Source: CDC)

ISOLATION Used to separate people infected with the virus (those who are sick with COVID-19 and those with no symptoms) from people who are not infected. (Source: CDC)

PROXIMITY TRACING or EXPOSURE NOTIFICATION Digital tools that automatically track the proximity of individuals and can notify people who were in close proximity to a positive case, using Bluetooth technology or GPS coordinates.

QUARANTINE Used to keep someone who might have been exposed to COVID-19 away from others. Quarantine helps prevent spread of disease that can occur before a person knows they are sick or if they are infected with the virus without feeling symptoms. (Source: CDC)

SUPPRESSION Reducing and maintaining low levels of disease transmission through intermittent loosening and tightening of public health and social measures (PHSMs); detection and isolation of cases, and contact tracing and quarantine.

TELEMEDICINE The delivery of health care services and information via electronic information and telecommunication technologies.

LIVING DOCUMENT This playbook is a dynamic, “living” document. Global knowledge pertaining to COVID-19 is rapidly evolving. Feedback and suggestions can be sent to

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