Colorado's new drive-through coronavirus-testing station in Denver made its debut Wednesday and was quickly overwhelmed. At one point Thursday, the line of cars with passengers waiting to be swabbed was almost four hours long, until the state cut off the service for the day.

Drive-through checks for Covid-19, with health workers in protective gear swabbing noses through car windows, was part of South Korea's largely successful strategy for containing the virus: The country tested more than 200,000 in a matter of weeks, a stark contrast to the U.S., where testing has proceeded at a crawl.

The nation's testing is "failing -- let's admit it," National Institute of Allergy and Infectious Diseases Anthony Fauci told Congress Thursday.

This week, a handful of states are deploying their own drive-through operations. New York opened its first Friday in New Rochelle, the epicenter of its outbreak. New Hampshire set up an operation this week.