When everyone who tests positive for coronavirus in your community gets a call from a public health worker asking them about their contacts, and those contacts are then asked to quarantine, that can be a powerful way to keep the virus from spreading.
But contact tracing can do more than that: At scale, the data gathered in those calls also offers vital information about where transmission is happening in a community. That data can drive policy, and even guide individuals in assessing what’s more or less safe to go out and do in their communities.
NPR has surveyed the health departments of all U.S. states and territories three times to ask about contact tracing capacity — first in April, then again in mid-June, and most recently in late July. The latest survey, done in collaboration with the Johns Hopkins Center for Health Security, also asked states about