- Lymphoma. Active central nervous system (CNS) infection by bacteria, varicella zoster virus, herpes simplex virus, or Cryptococcus neoformans. Any prior CNS infection due to Toxoplasma gondii. Any active life-threatening infection including Pneumocystis carinii pneumonia (PCP) (if prior PCP then pre-PCP arterial PO2 must be above 80), disseminated cryptococcosis (if there was a prior cryptococcosis infection the patient must have had a negative blood and cerebrospinal fluid (CSF) culture taken more than 6 weeks after the last antifungal therapy).