Viral meningitis, also known as aseptic meningitis, is a type of meningitis due to a viral infection. It results in inflammation of the meninges (the membranes covering the brain and spinal cord). Symptoms commonly include headache, fever, sensitivity to light and neck stiffness.Viruses are the most common cause of aseptic meningitis. Most cases of viral meningitis are caused by enteroviruses (common stomach viruses). However, other viruses can also cause viral meningitis, such as West Nile virus, mumps, measles, herpes simplex types I and II, varicella and lymphocytic choriomeningitis (LCM) virus. Based on clinical symptoms, viral meningitis cannot be reliably differentiated from bacterial meningitis, although viral meningitis typically follows a more benign clinical course. Viral meningitis has no evidence of bacteria present in cerebral spinal fluid (CSF). Therefore, lumbar puncture with CSF analysis is often needed to identify the disease.In most cases, there is no specific treatment, with efforts generally aimed at relieving symptoms (headache, fever or nausea). A few viral causes, such as HSV, have specific treatments. In the United States, viral meningitis is the cause of more than half of all cases of meningitis. With the prevalence of bacterial meningitis in decline, the viral disease is garnering more and more attention. The estimated incidence has a considerable range, from 0.26 to 17 cases per 100,000 people. For enteroviral meningitis, the most common cause of viral meningitis, there are up to 75,000 cases annually in the United States alone. While the disease can occur in both children and adults, it is more common in children.
However, in most cases, people infected with viruses that may cause meningitis do not actually develop meningitis.Viruses that can cause meningitis include:

Mechanism
Viral Meningitis is mostly caused by an infectious agent that has colonized somewhere in its host. People who are already in an immunocompromised state are at the highest risk of pathogen entry. Some of the most common examples of immunocompromised individuals include those with HIV, cancer, diabetes, malnutrition, certain genetic disorders, and patients on chemotherapy. Potential sites for this include the skin, respiratory tract, gastrointestinal tract, nasopharynx, and genitourinary tract. The organism invades the submucosa at these sites by invading host defenses, such as local immunity, physical barriers, and phagocytes or macrophages. After pathogen invasion, the immune system is activated. An infectious agent can enter the central nervous system and cause meningeal disease via invading the bloodstream, a retrograde neuronal pathway, or by direct contiguous spread. Immune cells and damaged endothelial cells release matrix metalloproteinases (MMPs), cytokines, and nitric oxide. MMPs and NO induce vasodilation in the cerebral vasculature. Cytokines induce capillary wall changes in the blood brain barrier, which leads to expression of more leukocyte receptors, thus increasing white blood cell binding and extravasation.The barrier that the meninges create between the brain and the bloodstream are what normally protect the brain from the bodys immune system. Damage to the meninges and endothelial cells increases cytotoxic reactive oxygen species production, which damages pathogens as well as nearby cells.