Several references provide estimates of the proportion of HCW infected with SARS-CoV2 that range from 0.9% -20%. A recent review from Alberta Health Services that examined the COVID-19 rt-PCR test results among HCW indicates that in that province 2.4% of physicians and 0.9% of non-MD HCW who were tested were positive for SARS-CoV-2 compared to 3.5% of the general population.
In the studies reviewed, the majority of cases are confirmed by RT-PCR, while only one reference also used serology testing.
Vanstone, J; Reeder, B; Duncan, V; Howell-Spooner, B. What proportion of healthcare workers are rt-PCR positive and IgM or IgG positive? 2020 Jun 2; Document no.: LAB040802v3 RR. In: COVID-19 Rapid Evidence Reviews [Internet]. SK: SK COVID Evidence Support Team, c2020. 10 p. (CEST rapid review report)