Medical scans of people suffering from COVID-19, the disease caused by the 2019 novel coronavirus currently sweeping the globe, can reveal how the virus attacks the lungs of an infected person.

In fact, the novel coronavirus appears to affect a person’s lungs in such a specific way, doctors can often tell if a patient has COVID-19 just by looking at their CT scans.

Reported in the journal Radiology, researchers at Tongji Hospital in Wuhan, the Chinese city where the outbreak was first reported, have gathered hundreds of chest CT scans from patients suffering from the viral disease.

Some of the clear indications of an infection are known as “ground-glass opacities”, which show the air spaces in the lungs are filling with liquid and a collapse of the lung’s alveoli, the tiny air sacs that exchange oxygen and carbon dioxide molecules to and from the bloodstream. These ground-glass opacities appear on CT scans like a cloudy blob, which can spread as the disease worsens in a “crazy pavement” pattern. You can see them in the CT scan below next to the small yellow arrows.

Chest CT images of a 29-year-old man who tested positive for SARS-CoV-2 on February 5, 2020. Yellow Arrows show ground-glass opacities in the bilateral lower lung lobes. Tao Ai et al/RSNA

Ground-glass opacities are fairly non-specific and can be found in a number of different infections and lung diseases. However, by looking at their shape and distributions, doctors can specifically identify cases of COVID-19.

In their study, the Chinese researchers studied over 1,000 patients with lung problems and found that chest CT scans were more effective at detecting COVID-19 than Reverse Transcriptase PCR, a lab test used to amplify and detect DNA and RNA sequences.

Many of the severe complications from COVID-19 arise from pneumonia, a condition characterized by inflammation of the air spaces in the lungs. This inflammation can cause the lung’s air sacs to flood with liquid and cells, resulting in shortness of breath, low oxygen levels, and a cough. Eventually, it can mean they don’t absorb enough oxygen into the bloodstream.

Chest CT images of a 34-year-old man with fever for 4 days who tested positive for SARS-CoV-2 on February 8, 2020. Tao Ai et al/RSNA

Another study details the case of a 44-year-old man who worked at the Huanan seafood market in Wuhan, China, the market where the outbreak is thought to have first jumped from animals to humans. Reported in the journal Radiology: Cardiothoracic Imaging in February 2020, the man was initially diagnosed with severe pneumonia and acute respiratory distress syndrome. After ruling out other pathogens, he was diagnosed with COVID-2019 and died just one week later. Once again, his chest CT scans showed clear signs of “patchy bilateral ground-glass opacities.”

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