CDC: The asymptomatic don’t need to be tested

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 pre-symptomatic

stage, before they start to feel ill — if they ever feel sick at all.

“This is potentially dangerous,” said Dr. Krutika Kuppalli, an infectious disease physician in Palo Alto, Calif. Restricting testing to only people with obvious symptoms of COVID-19 means “you’re not looking for a lot of people who are potential spreaders of disease,” she added. “I feel like this is going to make things worse.”

At a moment when experts have almost universally come forward to encourage more frequent and widespread testing, especially to reach vulnerable and marginalized sectors of the population, the CDC’s update appears counterintuitive and “very strange,” said Susan Butler-Wu, a clinical microbiologist at the Keck School of Medicine of the University of California.

Just weeks ago, the National Institutes of Health announced the first round of grant recipients for its Rapid Acceleration of Diagnostics program, or RADx, to scale up coronavirus testing in the coming weeks and months. On the agency’s RADx website, officials underscore the importance of prioritizing tests that can “detect people who are asymptomatic.”

A more lax approach to testing, experts said, could delay crucial treatments, as well as obscure, or even hasten, the coronavirus’s spread in the community.

“I think it’s bizarre,” said Daniel Larremore, a mathematician and infectious diseases modeler at the University of Colorado. “Any move right now to reduce levels of testing by changing guidelines is a step in the wrong direction.”

Prior iterations of the CDC’s testing guidelines struck a markedly different tone, stating that “testing is recommended for all close contacts” of people infected with the coronavirus, regardless of symptoms. The agency also specifically emphasized “the potential for asymptomatic and presymptomatic transmission” as an important factor in the spread of the virus.

The newest version, which was posted Monday, amended the agency’s guidance to say that people who have been in close contact with an infected individual — typically defined as being within 6 feet of a person with the coronavirus and for at least 15 minutes — “do not necessarily need a test” if they do not have symptoms. Exceptions, the agency noted, might be made for “vulnerable” individuals, or if health care providers or state or local public health officials recommend testing.

By the CDC’s own estimates, roughly 40% of people infected with the coronavirus may never go on to develop symptoms, remaining asymptomatic for the duration of their tenure with the virus. These numbers are tentative — and can’t be confirmed without more testing of people who appear entirely healthy.