Funding for this research was provided by:
the China Mega-Project for Infectious Diseases (2017ZX10101001)
National Science and Technology Support Program (2014BAI13B05)
Received: 6 June 2017
Accepted: 18 January 2018
First Online: 5 February 2018
Ethics approval and consent to participate
: The study was approved and consented by Ethics Committee of National Institute for Viral Disease Control and Prevention, China CDC. Written informed consent was obtained from adult participants and the legal guardian of the children participants.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.