While a half million Africans living with HIV have access to antiretroviral medication, health officials are concerned that long-term users of the meds may develop a resistance to them.

Health officials are already developing strategies to combat what they call a possible “major resistance phase” for the drugs. Treatment activists accuse South Africa’s health department for failing to correctly monitor the people taking ARVs and track resistance issues.

This vocalized concern comes at the heels of the dismissal of deputy health minister Nozizwe Madlala-Routledge, who was forced to step down just weeks ago.