Kidney transplant recipients are put on an immunosuppressant drug regimen to suppress their immune system which prevents allograft rejection. These drugs make the patient susceptible to infections. The opportunistic BK virus (BKV) infection has no effective antiviral treatment. The standard clinical practice to treat BKV is to reduce immunosuppression which in turn increases the risk of rejection. We use a mathematical model to predict the amount of BKV and develop an optical control method to provide individualized treatment to patients. We present the validation this model using data from the Duke Transplant center. We use multiple techniques for parameter estimation, including the Joint Unscented Kalman Filter.