Since aviation has been the vector for spreading the virus internationally, understanding what the disease is and how virulent it might be is the first step in understanding its spread and the consequences of that spread. Yes, there is a lot of chaff in some of the comments, but there is also useful information that can help us understand whether there is an over-reaction with the stoppage of flights into and out of China. There might also be information about the risks crew take in flying to infected areas. The spread is exponential (but not by a square factor) and may be slowed to an exponent less than 1 by breaking chains of infection, including not flying. Aviation is a key factor in this.