The follow-up CT examination in 52 patients showed that 3 patients who had negative baseline scan, rapidly progressed to with bilateral ground glass opacities. Since there is an incubation period after infection with the SARS-CoV-2 [15], a patient may not present any symptoms and imaging abnormalities during this period. At present, real-time PCR is used to confirm SARS-CoV-2 infection from respiratory secretions.