Funding for this research was provided by:
National Research Foundation (TTK20100723000013129)
Poliomyelitis Research Foundation (13/25)
Received: 24 April 2019
Revised: 4 June 2019
Accepted: 7 June 2019
First Online: 17 June 2019
Ethics approval and consent to participate
: This study obtained ethics from the University of Cape Town Faculty of Science Research Ethics Committee (SFREC 33_2012). All study participants provided written consent.
: Not applicable.
: The authors declare that they have no competing interests.