Cause of Encephalitis
In the United States, encephalitis causes can include enteroviruses, herpes simplex virus types 1 and 2, and arboviruses. Lyme disease can also be a cause of the disease. In the case of primary encephalitis, it is a direct viral infection of the spinal cord and brain. Where secondary encephalitis is concerned, encephalitis develops from complications of a current viral infection.
Most cases of encephalitis in the United States are caused by:
- Herpes simplex virus types 1 and 2
- A bite from a rabid animal (rabies virus)
- Arboviruses, which are transmitted from infected animals to humans through the bite of an infected tick, mosquito, or other blood-sucking insect.
Lyme disease, a bacterial infection spread by tick bite, can also be an encephalitis cause.
The cause of encephalitis depends on which type of the illness is involved. There are two types of encephalitis:
- Primary encephalitis (also called acute viral encephalitis) is caused by a direct viral infection of the spinal cord and brain. The infection may be focal (located in only one area) or diffuse (located in many different areas).
- Secondary encephalitis, also known as post-infective encephalitis, can result from complications of a current viral infection. Secondary encephalitis that results from an immunization or earlier viral infection is known as acute disseminated encephalitis. This illness often occurs two to three weeks following the initial infection.