Six Feet Is Not Enough and 15 Minutes Is Too Long
The coronavirus ignores this outdated social distancing measure
The U.S. Centers for Disease Control and Prevention (CDC) just updated its definition of “close contact” with a person infected with Covid-19 — wording that should influence how all of us think about social distancing, and which will change who gets traced and notified when someone tests positive. “Close contact” had been defined as 15 continuous minutes or more within six feet of an infectious individual, whether or not either person wore a mask and regardless of whether the contact occurred indoors or outside, though the CDC says those are important factors that affect transmission.
The new definition: 15 minutes or more of cumulative exposure to infectious individuals, within six feet, in a 24-hour period — such as three five-minute exposures — still regardless of masking and whether the contact was inside or outdoors.
The new recommendation was announced October 21, the same day the CDC published a case study of a correctional officer in Vermont thought to have caught the coronavirus via 22 brief encounters, within six feet of various infected inmates, all adding up to 17 minutes of exposure during an eight-hour shift.
Tom Frieden, former CDC director, calls the new definition a “sensible change.” “Makes a big difference for contact tracing efforts,” tweeted Syra Madad, PhD, an epidemiologist and director of the special pathogens program at NYC Health + Hospitals, a public health system. State and local health agencies, with varying degrees of effort and effectiveness, aim to trace and track down “close contacts” and urge them to quarantine. The federal government has no formal tracing plan.
“I have never believed that six feet is enough indoors without everyone wearing a mask,” says Richard Corsi, PhD, dean of the College of Engineering and Computer Science at Portland State University and an expert on indoor air quality. “I also do not buy that there is a ‘threshold’ dose that such guidance implies.”