. Author manuscript; available in PMC: 2019 May 15.
Published in final edited form as: Epidemics. 2018 Aug 29;26:23–31. doi: 10.1016/j.epidem.2018.08.002
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).