Fairfax County jumped from 80 to 124 known cases of coronavirus from Thursday to Friday.
As of this morning, the county has the highest number of presumptive cases, followed by Arlington County, which has 63 cases, according to the Virginia Department of Health.
An increase in testing capacity in the state could explain the increase in confirmed cases.
Inova Urgent Care locations in Chantille, Arlington and Tysons recently turned into respiratory illness clinics that offer the test.
Statewide, 604 cases of the virus have been identified of the 7,337 people who have been tested. Fourteen people have died from the respiratory illness, with one death in Fairfax County.
Fairfax County has not yet released its daily update on COVID-19 cases.