"It kind of looks like faint glass that has been ground up," Paras Lakhani, a radiologist at Thomas Jefferson University, told Business Insider. "What it represents is fluid in the lung spaces."
On its own, Lakhani said, ground glass isn't particularly helpful for identifying a coronavirus.
"You can see it with all types of infections — bacterial, viral, or sometimes even non-infectious causes," Lakhani said. "Even vaping could sometimes appear this way."
But the patches are significant, he added, when they extend to the edges of the patient's lungs.
"That's something we don't often see," Lakhani said. "We saw that with severe acute respiratory syndrome (SARS) and we saw that with Middle East respiratory syndrome (MERS)."
Both SARS and MERS are also coronaviruses. An outbreak of the former in China resulted in 8,000 cases and 774 deaths from November 2002 to July 2003.