closecontact

Close contact is a term used in epidemiology and public health to describe a situation in which a person is close enough to an infectious individual to have a non-negligible risk of transmitting the disease. The precise distance, time, and environmental conditions that define close contact vary by disease and by local guidance.

In public health practice, identifying close contacts helps determine who should be notified, offered testing, or isolated to prevent further spread. For many respiratory infections, close contact is defined as being within about 6 feet (2 meters) for a cumulative period of 15 minutes or more, especially in enclosed spaces, without appropriate protection. Some guidelines also count shorter encounters if there is direct exposure to infectious secretions or if the environment increases risk.

Close contact is contrasted with casual contact, which involves brief or distant exposure and is typically associated with a lower transmission risk.

In healthcare and workplace settings, close contact definitions guide infection-control measures, use of personal protective equipment, and contact tracing. The term is also used in digital contact tracing tools to estimate exposure duration and proximity, often leveraging proximity data and user-reported symptoms.

Because definitions depend on disease characteristics and jurisdiction, readers should consult local public health authorities for current criteria.