epidemic as has been observed in other epidemics of similar nature [2, 3].
It is a paradox that during the early period of an epidemic, little is known or available about the new infections; while the need for such information is at the highest level. This is particularly true for the COVID-19. The occurrence of this epidemic may follow a nonlinear, chaotic and catastrophic process, rather similar to the epidemic of SARS that occurred in Hong Kong in 2003 [2], the Ebola epidemic in West Africa during 2013–16 [4, 5], the pandemic of 2009 H1N1 epidemic started [6–8] and the recent measles outbreaks in the United States (US) [9]. Similar to an eruption of a volcano or occurrence of an earthquake, no matter how closely it is monitored, how much research we have done, how much we know about it, no one knows for sure if and when the virus infection will become an outbreak. Therefore, there is no so-called rational responses, no standard-operating-procedure (SOP) to follow, no measures to take without negative consequences [2].
However, defining the COVID-19 as nonlinear and chaotic does not mean that we cannot do anything after we knew it was an outbreak, but simply waiting. On the contrary, defining it as nonlinear and chaotic will better inform us to make right decisions and to take appropriate actions. (1) During the early stage of an infection