. Author manuscript; available in PMC: 2018 Mar 1.
Published in final edited form as: Epidemics. 2017 Mar;18:81–91. doi: 10.1016/j.epidem.2017.02.004
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).