Funding for this research was provided by:
Bill and Melinda Gates Foundation (ID OPP1083453)
Text and Data Mining valid from 2018-09-12
Received: 22 March 2018
Accepted: 29 August 2018
First Online: 12 September 2018
Compliance with ethical standards
: 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.
: The authors declare that they have no conflict of interest.