Contact tracing refers to the process of identification of persons who may have come into contact with an infected person and subsequent collection of further information about these contacts.
CT aims to reduce infections in the population by tracing the contacts of infected individuals, testing them for infection, isolating or treating the infected and tracing their contacts in turn.
CT commonly performed for disease:
tuberculosis, vaccine-preventable infections like measles, sexually transmitted infections (including HIV), blood-borne infections, Ebola, some serious bacterial infections, and novel virus infections; SARS-CoV, H1N1, and SARS-CoV-2.
CT goals:
To interrupt ongoing transmission and reduce the spread of an infection
To alert contacts to the possibility of infection and offer preventive/prophylactic care
To offer diagnosis, counseling and treatment to already infected individuals
If the infection is treatable, to help prevent reinfection of the originally infected patient
To learn about the epidemiology of a disease.
CT attempts to find all contacts of a confirmed case, to test or monitor them for infection.
Contact tracing has been a pillar of communicable disease control in public health for decades.
The eradication of smallpox was achieved not by universal immunization, but by exhaustive contact tracing to find all infected persons.
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.
A person with an identifiable communicable disease is often called the index case.
The index case is interviewed to learn about their movements, and whom they have been in close contact.
Contacts are identified, public health workers contact them to offer counseling, screening, prophylaxis, and/or treatment.
A contacts may be isolated or excluded from attending a particular location, if deemed necessary for disease control.
If contacts are not individually identifiable broader communications may be issued, like media advisories.
Direct public health involvement in notification is most effective.
For sexually transmitted infections, sexual contacts of the index case are relevant, as well aa babies born to the index case.
For blood-borne infections, blood transfusion recipients, contacts who shared a needle, and anyone else who could have been exposed to the blood of the index case are relevant.
For pulmonary tuberculosis, people living in the same household or spending a significant amount of time in the same room as the index case are relevant.
Contact tracing is most commonly used for control of diseases, but it is also a useful tool for investigating new diseases or unusual outbreaks in a particular community.
Contact tracing can help identify the etiology of a disease outbreak.
Reverse or retrospective tracing seeks to establish the source of an infection, by looking for contacts before infection, while forward tracing is the process of looking for contacts after infection, so as to prevent further disease spread.
Contact tracing can be related to issues of medical privacy and confidentiality.