. Author manuscript; available in PMC: 2016 Mar 1.
Published in final edited form as: Virology. 2015 Jan 28;477:32–41. doi: 10.1016/j.virol.2015.01.003
© 2015 Published by Elsevier Inc.
This manuscript version is made available under the CC BY-NC-ND 4.0 license.