Lungs affected by Covid-19 coronavirus. Axial computed tomography (CT) scans of human lungs affected by Covid-19 atypical pneumonia, with models of the coronavirus that causes the disease. The CT scans show peripheral 'ground glass opacities' (GGO), a diagnostic finding that indicates lung alveoli have filled with fluid. Covid-19 is a respiratory infection that can lead to fatal pneumonia. It is caused by the coronavirus SARS-CoV-2 (previously known as 2019-nCoV) which was first identified in Wuhan, China, in December 2019. The coronaviruses take their name from their crown (corona) of surface proteins, which are used to attach and penetrate their host cells. As of March 2020, the virus has spread to many countries worldwide. Around 90,000 have been infected with several thousand deaths.