Dr Viljoen is the sociobehavioural research lead at the Desmond Tutu TB Centre in the Dept of Paediatrics and Child Health. She has been working in the field of public health, particularly HIV, sexual reproductive health, stigma, and paediatric care in low-and middle-income countries. Partnering with various organisations, including NGOs, academic institutions, research organisations, and government bodies, she has implemented a broad scope of projects in diverse settings – including South Africa, Zambia, Mozambique, Ethiopia, Kenya, Tanzania, India and the Philippines.