  The temporal growth in the number of deaths in the COVID-19 epidemic is
subexponential. Here we show that a piecewise quadratic law provides an
excellent fit during the thirty days after the first three fatalities on
January 20 and later since the end of March 2020. There is also a brief
intermediate period of exponential growth. During the second quadratic growth
phase, the characteristic time of the growth is about eight times shorter than
in the beginning, which can be understood as the occurrence of separate
hotspots. Quadratic behavior can be motivated by peripheral growth when further
spreading occurs only on the outskirts of an infected region. We also study
numerical solutions of a simple epidemic model, where the spatial extend of the
system is taken into account. To model the delayed onset outside China together
with the early one in China within a single model with minimal assumptions, we
adopt an initial condition of several hotspots, of which one reaches saturation
much earlier than the others. At each site, quadratic growth commences when the
local number of infections has reached a certain saturation level. The total
number of deaths does then indeed follow a piecewise quadratic behavior.
