Details on the latest coronavirus death were not immediately available. The first two reported deaths were a 50-year-old man and a 46-year-old man, both with underlying health problems.
The latest death occurred when the county introduced a new online tool that provides a visual dashboard detailing the county's efforts.
So far, the county has evaluated 673 people and has 54 confirmed cases: 32 men and 22 women. Of these confirmed cases, 28 are between 18 and 49 years old, 17 are between 50 and 64 years old and nine are over 65 years old.
And starting Friday, San Bernardino County will begin driving tests for the new coronavirus.
Evidence would be available by appointment only, and enrollment and details were available on the county website.