HILLSBORO, Mo. — Mercy's third coronavirus testing site is now open in Jefferson County. 

The facility is at the Jefferson County fairgrounds, but not just everyone can drive up and get tested.

Potential patients first have to call 314-251-0500 to get screened by a healthcare professional.

You also need to meet CDC and state health department guidelines to be tested. That includes having a temperature of at least 100.4 degrees, respiratory symptoms like coughing or shortness of breath and recent travel to a high risk area. Other criteria to be eligible for a test includes being around someone who has tested positive for COVID-19.

RELATED: Missouri coronavirus testing criteria loosened, could allow more people to get tested

The testing center at the Jefferson County Fairgrounds is Mercy's third drive-thru site to open in the St. Louis area, the others are in Chesterfield and Washington. There also will be a location in south St. Louis County opening soon.

Once testing is complete at the drive-thru site, the kit will be sent to a lab. Depending on the lab, test results can come back as soon as two days or as long as a week.

The tests aren't free, but Mercy said most insurance companies, Medicare and Medicaid have committed to covering the cost.

"No one will be turned away from the testing site due to cost," Mercy said in a news release.

RELATED: List of coronavirus testing centers in the St. Louis area

Here are where all of Mercy's COVID-19 testing sites are or will be located:

Jefferson County:
Hillsboro Community Civil Club Jefferson County Fairgrounds
10349 Business 21, Hillsboro, Missouri

Washington:
Washington Fairgrounds
6 Fairgrounds Road, Washington, Missouri

Chesterfield:
Mercy Virtual Care Center
15740 S. Outer Forty Road, Chesterfield, Missouri

South St. Louis County: (opening is currently on hold)
MetLife building
13045 Tesson Ferry Road, St. Louis, Missouri