LCMV is most commonly recognized as causing neurological disease, as its name implies, though infection without symptoms or mild febrile illnesses are more common clinical manifestations.
For infected persons who do become ill, onset of symptoms usually occurs 8-13 days after exposure to the virus as part of a biphasic febrile illness. This initial phase, which may last as long as a week, typically begins with any or all of the following symptoms: fever, malaise, lack of appetite, muscle aches, headache, nausea, and vomiting. Other symptoms appearing less frequently include sore throat, cough, joint pain, chest pain, testicular pain, and parotid (salivary gland) pain.
Following a few days of recovery, a second phase of illness may occur. Symptoms may consist of meningitis (fever, headache, stiff neck, etc.), encephalitis (drowsiness, confusion, sensory disturbances, and/or motor abnormalities, such as paralysis), or meningoencephalitis (inflammation of both the brain and meninges). LCMV has also been known to cause acute hydrocephalus (increased fluid on the brain), which often requires surgical shunting to relieve increased intracranial pressure. In rare instances, infection results in myelitis (inflammation of the spinal cord) and presents with symptoms such as muscle weakness, paralysis, or changes in body sensation. An association between LCMV infection and myocarditis (inflammation of the heart muscles) has been suggested.
Previous observations show that most patients who develop aseptic meningitis or encephalitis due to LCMV survive. No chronic infection has been described in humans, and after the acute phase of illness, the virus is cleared from the body. However, as in all infections of the central nervous system, particularly encephalitis, temporary or permanent neurological damage is possible. Nerve deafness and arthritis have been reported.
Women who become infected with LCMV during pregnancy may pass the infection on to the fetus. Infections occurring during the first trimester may result in fetal death and pregnancy termination, while in the second and third trimesters, birth defects can develop. Infants infected In utero can have many serious and permanent birth defects, including vision problems, mental retardation, and hydrocephaly (water on the brain). Pregnant women may recall a flu-like illness during pregnancy, or may not recall any illness.
LCM is usually not fatal. In general, mortality is less than 1%.