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.

1. Sue Johnston DNP, RN, FNP-BC

2.  Infections of the central nervous system
(CNS) consist mainly of meningitis and
encephalitis and are caused by a variety of
pathologic microorganisms.
 High morbidity and mortality rates of
bacterial meningitis make diagnosis and early
treatment a high priority.
 Bacterial meningitis most common in
children < 2 with peak incidence at 3 – 8
months.
 Second peak incidence after 60 years of age.
 US annual incidence 2-5/100,000 persons

3.  Encephalitis is primarily caused by herpes
viruses (40%), arboviruses (insect
transmission), and enteroviruses.
 Peak incidence in the late summer months.
 Meningitis defined as either aseptic or septic,
depending on identification of bacteria on
the Gram stain or culture.
 Aseptic meningitis is caused primarily by
enteroviruses.
 Amebic meningoencephalitis is rare but
almost always fatal.

4.  Amebic meningioencephalitis-cont
 Caused by infection with Naegleria fowleri, free-
living ameba found in freshwater environments.
 Infection results from water containing N.
fowleri entering the nose, followed by migration
of the amebae to the brain via the olfactory
nerve.
 2007, six cases of PAM in the United States were
reported to CDC; all six patients died. cases,
which occurred in three southern tier states
(Arizona, Florida, and Texas) during June--
September