Funding for this research was provided by:
Centers for Disease Control and Prevention (U01-CE002531)
Received: 9 February 2018
Revised: 26 February 2019
Accepted: 26 February 2019
First Online: 15 July 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.