A high-risk close contact may be someone who:
Lived with a probable or confirmed case
Had prolonged (at least 15 minutes, cumulative), face-to-face contact (within 2 meters/6 feet) with a probable or confirmed case
Had direct contact with the infectious body fluids (i.e. droplets from a cough or sneeze) of a probable or confirmed case
Provided direct care to someone who has COVID-19
Has otherwise been identified by the local medical health officer as a possible contact
These contacts would not be high-risk if personal protective equipment (i.e. mask, eye protection, gloves) was used consistently and appropriately in these situations.
Interactions lasting less than 15 minutes (cumulative) are generally not considered close contact (ie. walking by or briefly being in the same room as a probable or confirmed case of COVID-19 would NOT be considered a high-risk contact).
Check out our post on what you should do if you live with someone with COVID-19.