“…This systematic review included 15 studies [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ] ( Table 1 ): seven studies were from Africa [ 18 , 19 , 20 , 21 , 23 , 24 , 25 ], six of which from Zaire, now called Democratic Republic of the Congo [ 18 , 19 , 20 , 21 , 24 ], three studies from the USA [ 22 , 29 , 30 ], one from Singapore [ 26 ], and three studies from Europe, one from United Kingdom [ 27 ] and two from Spain [ 28 , 32 ], respectively. One study had no reference to the country of origin [ 31 ].…”