We Still Don’t Fully Understand The Label ‘Asymptomatic’

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A CT Scan of the chest of a 66-year-old male reveals patchy rounded hazy spots throughout the lungs. He had tested positive for the novel coronavirus and experienced shortness of breath.

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Steven Needell/Science Source

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WHO Creates ‘Confusion’ About Asymptomatic Spread. Here’s What We Know

The findings are consistent with several studies following asymptomatic patients in China, which have found that many can develop lesions in the lungs despite having no outward symptoms, says Dr. Jennifer Taylor-Cousar, a pulmonologist at National Jewish Health in Denver not involved with the paper. «It probably is, at least in this disease, pretty common,» she says.

Doctors in New York have seen similar patterns. Dr. Jorge Mercado, a pulmonologist and critical care doctor at NYU Langone Hospital-Brooklyn who is not affiliated with the study, says he’s seen many instances where a patient has come to the hospital for a non-COVID-related issue and tested positive for the coronavirus. «Those patients evolved into what this paper illustrates, which is [their coronavirus infections] causing pneumonia, causing inflammatory changes,» he says.

Still, Taylor-Cousar cautions that researchers are studying the new coronavirus more intensively than they’ve studied other respiratory ailments. «Usually if someone is asymptomatic [with a common cold or flu virus], we would never even see them at all,» she says, «and we would never think to get a CT scan on them.» So there’s no comparable data to say whether the lung abnormalities are specific to asymptomatic coronavirus carriers, or common among respiratory viruses.

The patterns of lung disease seen on the CT scan can be caused by several factors. «It can be a little bit of fluid in the lungs, sometimes a little blood in a lung or sometimes just a small area of inflammation in the lung,» says Dr. Neil Schluger, chief of pulmonary, allergy and critical care medicine at the Columbia University Medical Center. «When I look at these images, I see what to me looks like small areas of inflammation that we see with many kinds of lung infections.»

For asymptomatic cases with mild lung inflammation and no other signs of illness, pulmonologists say they’re likely to kick the infection quickly and see no lasting lung damage.

«I suspect that, if you followed up with these asymptomatic people in several months, most of their CT scans would be completely normal unless they were known to later develop symptoms,» says Taylor-Cousar.

In the midst of an infection, however, doctors can’t predict how an individual’s case will progress. «There’s no way to know who is going to stop with an asymptomatic infection and likely recover completely and who is likely to go on to more severe infection,» says Schluger.

The Nature study also found pieces of the coronavirus in swab samples from asymptomatic patients for an average of 19 days — five days longer than a control group of mildly symptomatic patients. While it doesn’t necessarily mean asymptomatic people are infectious the whole time, it does suggest that they’re capable of spreading the virus to others at some point in their infections, says Schluger. «As we reopen society, that’s why it’s so important for people who are going out to wear a mask,» he says.