Encephalitis: Viral - Introduction

Introduction

Encephalitis is a rare but potentially life-threatening inflammation of the brain that can occur in people of all ages. The most common cause of encephalitis is infection by a virus. In very rare cases, encephalitis can also be caused by bacterial infection, parasites, or complications from other infectious diseases. This report focuses on viral encephalitis.

Encephalitis: Viral Infection of the Brain

Many viruses can cause encephalitis. The West Nile virus, for example, has been responsible for well-publicized outbreaks in the U.S. Most people exposed to encephalitis-causing viruses have no symptoms. Others may experience a mild flu-like illness, but do not develop full-blown encephalitis.

---

---

In severe cases, the infection can have devastating effects, including:

• Swelling of the brain (cerebral edema)
• Bleeding within the brain (intercerebral hemorrhage)
• Nerve damage (neuropathy)

The damage may cause long-term mental or physical problems, depending on the specific areas of the brain affected.

Other Viral Infections of the Central Nervous System. Viral infection and inflammation can affect multiple areas of the central nervous system, and is categorized by its location:

• Meningitis: infection of the meninges (the membranes that surround the brain and spinal cord)
• Meningoencephalitis: infection of both the brain and meninges
• Encephalomyelitis: infection of the brain and spinal cord

Specific Viruses Implicated in Encephalitis

Encephalitis caused by viruses in the United States generally fall into the following groups:

• Arboviruses are the primary cause of acute encephalitis (sudden-onset encephalitis caused by direct infection). Arboviruses, short for "arthropod-borne viruses," are spread by mosquitoes and ticks..
• Herpes viruses are the other major cause of encephalitis in the U.S. This virus family includes herpes simplex, Epstein-Barr, cytomegalovirus, and varicella-zoster.
• Enteroviruses, such as coxsackievirus, are viruses that enter the body through the gastrointestinal tract.
• In rare cases, secondary encephalitis can develop following childhood viral diseases such as measles, mumps, and rubella.