Lymphocytic choriomeningitis (LCM) is a viral disease spread from rodents to other rodents and humans. LCM can have serious effects on human fetuses during the first two trimesters and on people with suppressed immune systems.
The natural host for LCMV is the wild house mouse. Other rodents become infected by exposure to the house mouse. Pet mice, hamsters, and guinea pigs have also been identified as sources of infection for people. Less commonly infected animals are chinchillas, rats, rabbits, dogs, pigs, and primates.
LCMV is found in the feces, urine, saliva, semen, milk, and blood of infected rodents. It is also found in their nesting or bedding materials. Rodents and people become infected by coming in contact with any of these excretions. Transmission can occur through inhalation of aerosolized virus on dried material, by consumption, or through direct contact with the excretions. No person-to-person transmission has been documented, except for vertical transmission from mother to fetus. There has been one case reported of four people developing LCM after receiving organ transplants from a single donor who had purchased a pet hamster just before he died.
Many healthy people, nearly one-third of those infected with LCMV, will not develop any symptoms of illness. For healthy people who do become ill, nearly half of them will develop only mild symptoms, with no neurological involvement.
People who become more ill with LCM will develop a two-phase disease. The first phase is called the initial viremia stage. Symptoms appear 1 to 2 weeks after exposure to LCMV and include nonspecific, flulike symptoms, such as fever, lethargy, muscle pain, nausea and vomiting, headache, sore throat, and a nonproductive cough. This phase lasts up to a week.
The second phase of LCM is called the secondary viremia stage, which develops as the patient seems to recover from the first phase. It is characterized by a more severe headache, a stiff neck, and encephalitis, which is characterized by drowsiness, fever, confusion, nausea, and/or paralysis.
Women who become infected with LCMV during the first two trimesters of pregnancy can pass the virus to the fetus. This can result in fetal death or congenital problems such as hydrocephalus, microcephaly, or chorioretinitis.
People with suppressed immune systems, including people with HIV/AIDS, people receiving chemotherapy, organ transplant recipients, and people using steroids are at greater risk for developing a more severe illness.