Increasing testing capacity and ensuring rapid turnaround time (from symptoms, to testing, to test result delivery to both the patient and the health department) are key to “slowing the spread”.
Contact tracing will not prevent transmission from untested asymptomatic cases. Because asymptomatic testing accuracy and feasibility rates are still preliminary, even if communities do test asymptomatic contacts, negative results would not change quarantine recommendations. The CDC provides guidance on testing asymptomatic contacts of people diagnosed with COVID-19.