Folliculitis may recur even after symptoms have gone away. Symptoms of malaria can recur after varying symptom-free periods. While symptoms can resolve quickly, they can recur. Symptoms may recur and treatment for some days may be necessary. They can recur every few years or more frequently. Physical symptoms sometimes recur in the skin. This disease may recur following surgery and chemotherapy. However, symptoms usually recur after 6 to 9 months and progress rapidly. In some cases the infection may recur or become chronic. However, these differences do not continually recur. In such cases the cyst may recur. These patterns recur in different contexts and can sometimes be modelled mathematically. The condition may recur despite treatment. The illness may also recur after the initial outbreak. In captivity, estrous cycles recur every 15 days.