Illustration of SARS-CoV-2 coronavirus particles. SARS-CoV-2 is an enveloped RNA (ribonucleic acid) virus. Within the membrane are spike proteins (centre, large dark spikes), membrane proteins and envelope proteins. SARS-CoV-2 causes the respiratory infection Covid-19, which can lead to fatal pneumonia. SARS-Cov-2 virus. The three surface proteins are depicted in blue. The biggest one is the spike (S) protein. The structures of the proteins are derived from X-ray diffraction data. PDB entry 6vsb.