Encephalitis may be caused by a variety of afflictions. One such affliction is rabies. Encephalitis may also be caused by HIV. The major causes of encephalitis outbreaks all over the world are viruses like Japanese Encephalitis, West Nile, Chandipura virus, St. Louis Encephalitis, Equine Encephalitis, La Crosse encephalitis, Murray Valley encephalitis virus, California encephalitis virus, Tick-borne meningoencephalitis, Herpes simplex, Influenza A virus. Less common are e.g. RSSE (Russian spring-summer encephalitis) viruses.
Neurological examinations usually reveal a drowsy or confused patient. Stiff neck, due to the irritation of the meninges covering the brain, indicates that the patient has either meningitis or meningeoncephalitis. Examination of the cerebrospinal fluid obtained by a lumbar puncture procedure usually reveals increased amounts of protein and white blood cells with normal glucose, though in a significant percentage of patients, the cerebrospinal fluid may be normal. CT scan often is not helpful, as cerebral abscess is uncommon. Cerebral abscess is more common in patients with meningitis than encephalitis. Bleeding is also uncommon except in patients with herpes simplex type 1 encephalitis. Magnetic resonance imaging offers better resolution. In patients with herpes simplex encephalitis, electroencephalograph may show sharp waves in one or both of the temporal lobes. Lumbar puncture procedure is performed only after the possibility of prominent brain swelling is excluded by a CT scan examination. Diagnosis is often made with detection of antibodies in the cerebrospinal fluid against a specific viral agent (such as herpes simplex virus) or by polymerase chain reaction that amplifies the RNA or DNA of the virus responsible (such as varicella zoster virus).
Encephalitis lethargica is an atypical form of encephalitis which caused an epidemic from 1917 to 1928, resulting in millions of deaths worldwide. Those who survived sank into a semi-conscious state that lasted for decades until the Parkinsons drug L-dopa was used to revive those still alive in the late 1960s by Oliver Sacks.
There have been only a small number of isolated cases in the years since, though in recent years a few patients have shown very similar symptoms. The cause is now thought to be either a bacterial agent or an autoimmune response following infection.
Herpes simplex encephalitis is caused by the herpes simplex virus that manifests in oral cold sores or genital sores. When this triggers brain inflammation, which occurs in 10% of cases of encephalitis (2 cases per million people), half of all untreated patients die (1 case per million people). Brain damage, partial paralysis, seizures, hallucinations and an altered state of consciousness are all common symptoms. HSE can be passed from mother to child during birth in rare cases, where symptoms include lethargy, tremors, irritability, seizures and poor feeding in the first two weeks after birth.