SARS-CoV-2 in humans

The novel coronavirus SARS-CoV-2 became pandemic at the beginning of 2020, and caused about 80 million cases and more than 1.8 million deaths by the end of the year. As its relatives MERS- and SARS-CoV, but in contrast to the four human coronaviruses circulating worldwide, SARS-CoV-2 in a sizeable fraction of cases leads to a severe and potentially life-threatening disease, called COVID-19. Since in addition this virus is very contagious, particularly prior to onset or in absence of symptoms, and pre-existing immunity appears to be largely absent or at least of very little relevance, it is spreading rapidly in the population. A hallmark of COVID-19 is an at least partially detrimental immune response that not only can lead to serious lung damage, but may also damage organs outside the respiratory tract such as the heart and kidneys. This review summarizes current knowledge about the virus and the disease it causes, and outlines open questions in the different research fields.