Central nervous system infections like meningitis and encephalitis are caused by various microorganisms and can have high mortality rates, making early diagnosis and treatment important. Bacterial meningitis is most common in children under 2 years old and adults over 60. It has an annual incidence rate in the US of 2-5 per 100,000 people. Encephalitis is primarily caused by herpes viruses, arboviruses, and enteroviruses, and has a peak incidence in late summer. Amebic meningoencephalitis, caused by the ameba Naegleria fowleri found in freshwater, is rare but fatal.