Measurement of the amount of virus a person is exposed to. Generally, the greater the dose, the greater the likelihood of infection.

With COVID-19 an exposure dose or infective dose is the amount of SARS-CoV-2 virus that a person breathes in from the environment that is required to cause infection.  It’s not yet known what the infective dose is for SARS-CoV-2.

Timing, proximity, and air movement influence exposure. People with SARS-CoV-2 are most infectious in the one to two days before they develop symptoms. Conversing with them, within a distance of 3-6 feet (1-1.8 metes) in an unventilated space greatly increases the probability of exposure to an infective dose, particularly when neither person wears a mask.  



Infectious Disease Transmission