Many numbers related to the coronavirus in D.C., Maryland and Virginia are shared each day, and all of the data can be confusing.

Sometimes, it looks like the number of COVID-19 cases is spiking, when in fact that may not be the case.

In Virginia’s Fairfax County, for example, work on the system used to report disease data resulted in a smaller number of reported new cases Sunday and a spike in newly-reported cases Monday.

So, what do all the numbers really mean? What do antibody tests tell? Why is there such variation in results from day to day?

WTOP asked Dr. Rene Najera, a Fairfax County Health Department epidemiologist, for the answers to some of the biggest questions about COVID-19 and other pandemic concerns.