I'm quoting from clinicians who know far more about it than you two.
From the European Centre for Disease Prevention and Control, Stockholm, 2020
High-risk exposure (close contacts*)
- A person living in the same household as a COVID-19 case
- A person having had direct physical contact with a COVID-19 case (e.g. shaking hands)
- A person having unprotected direct contact with infectious secretions of a COVID-19 case (e.g. being
coughed on, touching used paper tissues with a bare hand)
- A person having had face-to-face contact with a COVID-19 case within 2 metres [2] and > 15 minutes
- A person who was in a closed environment (e.g. classroom, meeting room, hospital waiting room, etc.)
with a COVID-19 case for 15 minutes or more and at a distance of less than 2 metres
- A healthcare worker (HCW) or other person providing direct care for a COVID-19 case, or laboratory
workers handling specimens from a COVID-19 case without recommended PPE or with a possible breach
of PPE [3]
- A contact in an aircraft sitting within two seats (in any direction) of the COVID-19 case, travel companions
or persons providing care, and crew members serving in the section of the aircraft where the index case was seated [4] (if severity of symptoms or movement of the case indicate more extensive exposure, passengers seated in the entire section or all passengers on the aircraft may be considered close contacts)
- 2. Low-risk exposure (casual contact)
- A person who was in a closed environment with a COVID-19 case for less than 15 min or at a distance of more than 2 metres
- A person having had face-to-face contact with a COVID-19 case for less than 15 min and at a distance of less than 2 metres
- Traveling together with a COVID-19 case in any kind of conveyance.
Longer duration of contact increases the risk of transmission; the 15-minute limit is arbitrarily selected for practical purposes. Based on individual risk assessments, public health authorities may consider expanding contact tracing and management to persons who had a shorter duration of contact with a case.
IN A NUTSHELL: PROLONGED EXPOSURE TO PEOPLE IN A CONFINED SPACE > THE LIKELIHOOD OF TRANSMISSION.