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Lymphocytic choriomeningitis is caused by an arenavirus. It usually causes a flu-like illness or aseptic meningitis, sometimes with rash, arthritis, orchitis, parotitis, or encephalitis. Diagnosis is by viral isolation or indirect immunofluorescence. Treatment is supportive.
Lymphocytic choriomeningitis is endemic in rodents. Human infection results most commonly from exposure to dust or food contaminated by the gray house mouse or hamsters, which harbor the virus and excrete it in urine, feces, semen, and nasal secretions. When transmitted by mice, the disease occurs primarily in adults during autumn and winter.
The incubation period is 1 to 2 wk. Most patients have no or minimal symptoms. Some develop a flu-like illness. Fever, usually 38.5 to 40° C, with rigors is accompanied by malaise, weakness, myalgia (especially lumbar), retro-orbital headache, photophobia, anorexia, nausea, and light-headedness. Sore throat and dysesthesia occur less often. After 5 days to 3 wk, patients may improve for 1 or 2 days. Many relapse with recurrent fever, headache, rashes, swelling of metacarpophalangeal and proximal interphalangeal joints, meningeal signs, orchitis, parotitis, or alopecia of the scalp.
Aseptic meningitis occurs in a minority of patients. Rarely, frank encephalitis, ascending paralysis, bulbar paralysis, transverse myelitis, or acute Parkinson disease can occur. Neurologic sequelae are rare in meningitis but occur in up to 33% of patients with encephalitis. Infection during pregnancy may cause fetal abnormalities, including hydrocephalus, chorioretinitis, and intellectual disability.
Lymphocytic choriomeningitis is suspected in patients with exposure to rodents and an acute illness, particularly aseptic meningitis or encephalitis. Aseptic meningitis may lower CSF glucose mildly but occasionally to as low as 15 mg/dL. CSF WBCs range from a few hundred to a few thousand cells, usually with > 80% lymphocytes. WBC counts of 2000 to 3000/μL and platelet counts of 50,000 to 100,000/μL typically occur during the first week of illness.
Diagnosis can be made by isolating the virus from the blood or CSF or by indirect immunofluorescence assays of inoculated cell cultures, although these tests are most likely to be used in research laboratories. Diagnosis can also be made by detecting seroconversion of antibody to the virus.
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