Funding for this research was provided by:
Centers for Disease Control and Prevention (1-U48-DP-000040)
Received: 22 September 2019
Accepted: 21 November 2019
First Online: 4 December 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 review board at the Johns Hopkins School of Public Health (IRB #NA 00021362) 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.