encephalitisArticle Free Pass encephalitis, plural
encephalitides, from Greek enkephalos (“brain”) and itis
(“inflammation”), inflammation of the brain. Inflammation
affecting the brain may also involve adjoining structures;
encephalomyelitis is inflammation of the brain and spinal cord,
and meningoencephalitis is inflammation of the brain and
meninges (the membranes covering the brain). Encephalitis is
most often caused by an infectious organism and sometimes by
such noninfective agents as chemicals, including lead, arsenic,
and mercury. Although encephalitis can be produced by many
different types of organisms, such as bacteria, protozoans, and
helminths (worms), the most frequent causal agents are viruses.
The encephalitis-producing viruses are divided into two groups:
(1) those that invade the body and produce no damage until they
are carried by the bloodstream to the nerve cells of the brain
(e.g., the rabies and arthropod-borne viruses) and (2) those
that invade the body and first injure nonnervous tiss