Bad News: 54% of asymptomatic cases and 79% of COVID-19 symptomatic cases on the Diamond Princess had ground-glass abnormalities in their CT scans.

https://pubs.rsna.org/doi/10.1148/ryct.2020200110

"And here is what really surprised us: These patients did not report any sensation of breathing problems, even though their chest X-rays showed diffuse pneumonia and their oxygen was below normal. How could this be?"

"We are just beginning to recognize that Covid pneumonia initially causes a form of oxygen deprivation we call “silent hypoxia” — “silent” because of its insidious, hard-to-detect nature." https://www.nytimes.com/2020/04/20/opinion/coronavirus-testing-pneumonia.html