Illustration: Kieran Blakey

The Nuance

Even If You’re Asymptomatic, the Coronavirus Can Do Damage

New research on asymptomatic people reveals underlying effects

Markham Heid
Published in
4 min readJun 25, 2020

Since the early days of the novel coronavirus outbreak, infectious disease experts have recognized that some people who contract the virus do not develop a fever, cough, or any of the infection’s other hallmark symptoms.

These apparently “asymptomatic” cases may make up a large portion of all Covid-19 infections. Estimates vary widely, but many — including a recent mathematical model from the U.S. Centers for Disease Control and Prevention (CDC) — suggest that somewhere between 20% and 50% of infectees never experience noticeable symptoms.

This is a problem for public health officials because asymptomatic carriers can likely still spread the virus to others. Their lack of apparent symptoms makes the virus tricky to monitor and corral. On the other hand, it would be comforting if a large percentage of people with Covid-19 are skating through without any apparent ill effects.

But some recent findings have turned up “subclinical” effects in people with Covid-19 who never develop noticeable virus symptoms. These could indicate underlying risks for asymptomatic patients.

“No one is really assessing those organs in asymptomatic people. So we just don’t know what’s going on.”

Trouble below the surface

According to a recent research review published in the Annals of Internal Medicine, chest scans of asymptomatic people with Covid-19 have revealed the presence of some “lung abnormalities” — abnormalities that also turn up among symptomatic patients.

Specifically, the scans have found what radiologists call “ground-glass opacities” — or GGOs — which are areas of lung tissue that appear gritty and opaque (like ground glass), and that tends to develop as a result of…



Markham Heid

I’m a long-time contributor at TIME and other media orgs. I write mostly about health. I grew up in Michigan, but these days I live in southwest Germany.