Contact tracing is used by health departments to prevent the spread of infectious diseases. In general, contact tracing involves identifying people who have a confirmed or probable case of COVID-19 (cases) and people who they came in contact with (close contacts) and working with them to interrupt disease spread. This includes asking people with COVID-19 to isolate and their contacts to quarantine at home voluntarily. Fully vaccinated persons who remain asymptomatic and those with documented COVID-19 infection within the past 90 days are excluded from quarantine. However, the new CDC guidance recommends that fully vaccinated persons test three to five days after the known exposure and wear a mask in public indoor settings for 14 days after exposure or until a negative test result.
For all individuals where exposure occurred outside of the classroom setting and for teachers, staff and adults in the indoor P-12 classroom setting, CDC defines a close contact as an individual not fully vaccinated against COVID-19 who was within 6 feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period. For students in the indoor classroom setting, contacts who were within 3 to 6 feet of an infected student do not require quarantine as long as both the case and the contact were consistently masked. If they were not consistently masked, then close contacts are classroom students who were within 6 feet of the infected student for a cumulative total of 15 minutes or more over a 24-hour period.
In general, individuals who are solely exposed to a confirmed case while outdoors should not be considered close contacts.
The longer a person is exposed to an infected person, the higher the risk of exposure/transmission. The infectious period of close contact begins two calendar days before the onset of symptoms (for a symptomatic person) or two calendar days before the positive sample was obtained (for an asymptomatic person). If the case was symptomatic (e.g., coughing, sneezing), persons with briefer periods of exposure may also be considered contacts, as determined by local health departments. Persons who have had lab-confirmed COVID-19 within the past 90 days or those fully vaccinated who remain asymptomatic, according to CDC guidelines, are not required to quarantine if identified as a close contact to a confirmed case.
Local health departments are the final authority on identifying close contacts (IDPH, August 2021).