[1] Univ Witwatersrand, Fac Hlth Sci, Dept Crit Care & Paediat Allergy Clin, Dept Emergency Med, ZA-2050 Johannesburg, South Africa
[2] Charlotte Maxeke Johannesburg Acad Hosp, Johannesburg, South Africa
[3] Univ Witwatersrand, Fac Hlth Sci, Dept Emergency Med, ZA-2050 Johannesburg, South Africa
[4] Univ Witwatersrand, Fac Hlth Sci, Dept Paediat & Paediat Allergy Clin, ZA-2050 Johannesburg, South Africa