Funding for this research was provided by:
London School of Hygiene and Tropical Medicine (NA)
Received: 15 February 2019
Accepted: 26 July 2019
First Online: 4 September 2019
Ethics approval and consent to participate
: Ethical approval was obtained from Ethics Committee of London School of Hygiene and Tropical Medicine. All participants provided informed verbal consent to take part in the study.
: Not applicable.
: The authors declare that they have no competing interests.