In public health, contact tracing is the process of identification of persons who may have come into contact with an infected person ("contacts") and subsequent collection of further information about these contacts. By tracing the contacts of infected individuals, testing them for infection, treating the infected and tracing their contacts in turn, public health aims to reduce infections in the population. Diseases for which contact tracing is commonly performed for include tuberculosis, vaccine-preventable infections like measles, sexually transmitted infections (including HIV), blood-borne infections, some serious bacterial infections, and novel infections (e.g. SARS and the Novel coronavirus (2019-nCoV)).

The goals of contact tracing are:

Contact tracing has been a pillar of communicable disease control in public health for decades. The eradication of smallpox, for example, was achieved not by universal immunization, but by exhaustive contact tracing to find all infected persons.[1] This was followed by isolation of infected individuals and immunization of the surrounding community and contacts at-risk of contracting smallpox.

In cases of diseases of uncertain infectious potential, contact tracing is also sometimes performed to learn about disease characteristics, including infectiousness. Contact tracing is not always the most efficient method of addressing infectious disease. In areas of high disease prevalence, screening or focused testing may be more cost-effective.

Partner notification, also called partner care, is a subset of contact tracing aimed specifically at informing sexual partners of an infected person and addressing their health needs.