What Is Lymphocytic Choriomeningitis?

Medically Reviewed by Mahammad Juber, MD on October 14, 2022
Written by Parang Mehta
5 min read

Lymphocytic choriomeningitis is a viral disease that sometimes affects the nervous system. The lymphocytic choriomeningitis virus typically infects rodents first, most frequently the common house rat. You are at risk of this infection if you have pet rodents or come into contact with wild ones. This disease is common in the Americas, Europe, Australia, and many other regions.

The lymphocytic choriomeningitis virus is an RNA virus belonging to the arenaviridae family. Infection by this virus can result in viral clearance, viral persistence in the body, immune suppression, hepatitis (liver inflammation and damage), or choriomeningitis. Individual symptoms depend on the lymphocytic choriomeningitis virus strain, the size of the infecting dose, and the route of the infection.

Lymphocytic choriomeningitis is a viral disease that primarily affects rodents. Infected mice, rats, guinea pigs, or hamsters may remain healthy-looking or look sick. Some animals have the infection for months before showing signs of illness. At that point, they will have red eyes, their coat will become rough, and their appetite will decrease. 

House mice (Mus musculus) can carry the lymphocytic choriomeningitis virus throughout their lives without any sign of illness. As a result, they're able to transmit the infection as long as they live.

Your pet hamsters or mice can both infect you if they carry the disease. However, wild rodents are more likely to be infected. Urine, saliva, droppings, and nesting materials can all contain the virus. You may be infected if these infectious materials come in contact with wounds or damaged skin. Animal bites or contact with the mucus membranes of the mouth, nose, or eyes can also transmit the infection.

The lymphocytic choriomeningitis virus does not spread person-to-person under most circumstances. If you get this infection, you're not a threat to people in your home or workplace, though the virus can spread from the placenta to an unborn baby during pregnancy. Infections of a baby in the womb may lead to:

  • Congenital hydrocephalus (accumulation of fluid in the brain)
  • Mental retardation
  • Chorioretinitis (inflammation and damage of structures within the eyes)
  • Microcephaly (an abnormally small head because of brain damage or poor development in the womb)
  • Vision defects

Organ transplants can also transmit the lymphocytic choriomeningitis virus.

Exposure to the lymphocytic choriomeningitis virus is common. About 5% of the population is infected with this virus, but most people have no symptoms and do not feel sick. You're not likely to experience systems if your immune system is strong. People with weakened immune systems and pregnant people, though, are at risk for infection and severe disease, and infected organ transplant recipients are at risk for death.

The lymphocytic choriomeningitis virus can cause severe illness, though almost all healthy people recover. The death rate from this virus is less than 1%.

If you get infected, you're most likely to show no symptoms or just a mild fever. If you get sick, it'll happen 8 to 13 days after exposure to the rodent infectious material. The illness caused by the lymphocytic choriomeningitis virus is biphasic — i.e., the illness occurs in two distinct phases separated by a few days without fever.

The first phase lasts up to a week and consists of a fever, body aches, a lack of appetite, headaches, nausea, and vomiting. You may also have a sore throat, cough, chest pain, joint pain, and salivary gland pain.

The lymphocytic choriomeningitis virus also affects the central nervous system. This virus is not cytopathic, though — it does not kill brain cells. Still, it generates a strong immune response that causes enormous numbers of white blood cells to accumulate in the brain. These cells release various chemicals and enzymes that cause inflammation and damage in the meninges (the membranes covering the brain) and the brain itself.

In the second phase, you may experience symptoms of encephalitis (confusion, drowsiness, paralysis, etc.), meningitis (fever, headache, stiff neck, etc.), or both. Another complication, myelitis, is an inflammation of the spinal cord and causes muscle weakness, paralysis, and disordered sensation. Acute hydrocephalus (collection of fluid in the brain) can also occur and requires surgery for urgent relief.

Most people with meningitis or encephalitis recover, but as with many conditions affecting the nervous system, there may be troublesome long-term problems. For instance, the lymphocytic choriomeningitis virus sometimes causes deafness or arthritis.

If you have rodent pets at home or work with animals, you are at risk for this infection. Consult your doctor if you have any symptoms. The symptoms are very similar to many other viral diseases, though, so your doctor may perform some tests to make a diagnosis and see if:

  • A total blood count shows leukopenia (low white blood cell count) and thrombocytopenia (reduced platelet count).
  • Liver enzymes have increased.
  • A spinal tap for cerebrospinal fluid (CSF) examination shows increased white cells and a reduced glucose level.
  • Specific antibodies appear in the CSF and blood samples.
  • A polymerase chain reaction (PCR) indicates the presence of the lymphocytic choriomeningitis virus.

Your doctor will supply you with at-home treatments if you have mild disease. They will prescribe medicines to control your fever, headache, vomiting, and other symptoms. On the other hand, cases of meningitis, encephalitis, or meningoencephalitis will require hospitalization in addition to supportive treatment.

Specific antiviral treatment is not recommended for lymphocytic choriomeningitis virus disease. Ribavirin, an antiviral medicine, has been shown to be effective in the laboratory, but there is no evidence that it is effective in humans.

Some precautions can keep you safe from this dangerous infection:

  • Make sure your pet animals don't have contact with wild rodents, including their droppings or nests. Seal up all entry holes through which wild animals can enter. 
  • Avoid contact with wild animals. 
  • Wear gloves when cleaning mice cages and handling dead or live mice.
  • Keep rodent cages free from soiled bedding. Clean them outside the house or in well-ventilated areas.
  • Always wash your hands thoroughly after any contact with rodents.
  • Don't kiss a pet rodent or hold it close to your face.

Certain people particularly need to avoid contact with rodents. Other family members should be asked to care for any pets and clean their cages. Such precautions are advisable in the cases of:

The Centers for Disease Control and Prevention (CDC) does not advise testing your pets for the lymphocytic choriomeningitis virus because these tests are undependable, so if you are worried about catching the lymphocytic choriomeningitis virus from your pet, you should find someone to adopt them. Pet rodents shouldn't be released into the wild.