Warning, heavy-duty COVID link ahead: The Risks - Know Them - Avoid Them
In order to get infected you need to get exposed to an infectious dose of the virus; based on infectious dose studies with MERS and SARS, some estimate that as few as 1000 SARS-CoV2 viral particles are needed for an infection to take hold. Please note, this still needs to be determined experimentally, but we can use that number to demonstrate how infection can occur. Infection could occur, through 1000 viral particles you receive in one breath or from one eye-rub, or 100 viral particles inhaled with each breath over 10 breaths, or 10 viral particles with 100 breaths. Each of these situations can lead to an infection.
Certainly not light reading, but essential.