ウイルス性髄膜炎

Enteroviruses are the primary causative agents of viral meningitis, particularly coxsackieviruses and echoviruses. These small, non-enveloped, positive-sense single-stranded RNA viruses belong to the Picornaviridae family. Their cytolytic nature allows them to persist in harsh environmental conditions, including chlorinated water, facilitating transmission through contaminated surfaces and hands.

After replicating in gastrointestinal epithelial cells, enteroviruses enter the bloodstream and cross protective barriers via two routes. They may infect blood-brain barrier endothelial cells directly, or pass through the choroid plexus epithelium to access cerebrospinal fluid. Once in the CSF, viruses activate immune cells to release cytokines, triggering meningeal inflammation.

Viral meningitis presents with fever, headache, and stiff neck as primary symptoms. Additional manifestations include drowsiness, nausea, photophobia, and vomiting. While generally milder than bacterial meningitis, rare severe complications or death may occur, though most patients recover within 7-10 days without specific antiviral therapy.

Viral meningitis shows lymphocytic predominance with normal or mildly elevated protein and normal glucose levels in cerebrospinal fluid. Bacterial meningitis, by contrast, displays elevated neutrophil count, high protein levels, and low glucose. These CSF differences help distinguish between viral and bacterial forms during diagnosis through lumbar puncture.

Viral meningitis is usually self-limiting and requires only supportive care including hydration, rest, and symptom relief. Bacterial meningitis, conversely, is a medical emergency demanding prompt antibiotic treatment to prevent severe complications or death. Most viral meningitis patients recover completely within 7-10 days without specific antiviral therapy or long-term complications.

Viral meningitis peaks during late summer and early fall, though it remains underreported due to its mild course. Enteroviral shedding can persist for weeks, with patients remaining infectious for up to 10 days. Despite its contagious nature and fecal-oral transmission route, the condition's prevalence exceeds bacterial or fungal meningitis forms.

Once enteroviruses reach cerebrospinal fluid, they activate host immune cells to release cytokines. These signaling molecules recruit additional immune cells to the meninges, driving the inflammatory response. This immune activation produces the characteristic symptoms of headache, fever, and neck stiffness associated with viral meningitis.