. Author manuscript; available in PMC: 2017 Jul 11.
Published in final edited form as: Virology. 2017 Mar 21;506:34–44. doi: 10.1016/j.virol.2017.03.002
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/).