Funding for this research was provided by:
Medical Research Council (MRC/ESRC Interdisciplinary 1+3 Studentship)
Received: 21 December 2017
Accepted: 21 November 2018
First Online: 20 December 2018
Ethics approval and consent to participate
: The study received ethical approval from the London School of Hygiene and Tropical Medicine Ethics Committee, with application number 5922. Written informed consent was obtained from all 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.