The revision prompted confusion and alarm from experts, who called the move “potentially dangerous.”
The Centers for Disease Control and Prevention quietly modified its coronavirus testing guidelines this week to exclude people who do not have symptoms of Covid-19 — even if they have been recently exposed to the virus.
Experts questioned the revision, pointing to the importance of identifying infections in the small window immediately before the onset of symptoms, when many individuals appear to be most contagious.
Models suggest that about half of transmission events can be traced back to individuals still in this so-called pre-symptomatic stage, before they start to feel ill — if they ever feel sick at all. Continue reading.