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Illustration of the ultrastructure of the SARS-CoV-2 coronavirus (previously 2019-nCoV) that was first identified in Wuhan, China, in December 2019. It is an enveloped RNA (ribonucleic acid) virus. Within the membrane are spike proteins (orange), membrane proteins (red) and envelope proteins (yellow). SARS-CoV-2 causes the respiratory infection Covid-19, which can lead to fatal pneumonia. (KEYSTONE/SCIENCE PHOTO LIBRARY/KATERYNA KON/SCIENCE PHOTO LIBRARY)