Abstract
A severe respiratory disease emerged in the city of Wuhan, Hubei province, China, in December 2019. As of early February 2020, at least 28,088 diagnosed and 24,702 suspected cases have been reported, including at least 564 deaths. Unfortunately, the disease has spread globally. The etiologic agent, a novel coronavirus, now called SARS-CoV-2, was immediately identified and characterized in China. Although we know the presence of unprecedented genetic diversity of viruses in nature, this outbreak further indicates that there is considerable uncertainty in predicting when, where, and how novel disease-causing pathogens emerge. Phylogenetic analyses reveal that SARSCoV-2 is closely related to a group of SARSlike coronaviruses. However, it remains unclear where the virus comes from and how it was transmitted to humans in the first place. Unlike with other zoonotic agents such as hantavirus and arenavirus, thus far we haven’t found a SARS virus in animals that is the same as that in humans. Fortunately, SARS virus has not appeared in humans since 2004. In contrast, this new virus seems to have stronger transmission capabilities among people. Compared to the primary virus in humans, we still know less about whether, what, and how the virus has changed and the effect of the changes for their epidemics in humans. Control and prevention of the disease is especially difficult in China and elsewhere if there are infected individuals with no clinical signs.
