If widespread testing is the first step toward getting control over this pandemic, then the second step is contact tracing. But a virus that can spread without symptoms poses special challenges. With sexually transmitted infections, the list of potential contacts is finite, and mostly knowable. With COVID-19, that list would include people who visited the supermarket at the same time as you, people who have touched your building's doorknob. So the teams of contact tracing investigators being amassed around the country have their work cut out for them.

On today's show, David Harvey, executive director of the National Coalition of STD Directors (NCSD), talks about what tracing entails, why it's important and how it's been used to abate the damage of other diseases like HIV, Zika and Ebola.