Initially, at low levels of resistance and with a low prevalence of malaria, the impact of resistance to antimalarials is insidious. The initial symptoms of the infection resolve and the patient appears to be better for some weeks. When symptoms recur, usually more than two weeks later, anaemia may have worsened and there is a greater probability of carrying gametocytes (which in turn carry the resistance genes) and transmitting malaria. However, the patient and the treatment provider may interpret this as a newly acquired infection. At this stage, unless clinical drug trials are conducted, resistance may go unrecognized. As resistance worsens the interval between primary infection and recrudescence shortens, until eventually symptoms fail to resolve following treatment. At this stage, malaria incidence may rise in low-transmission settings and mortality is likely to rise in all settings.