Viral Meningitis

Overview

By Tina Shahian, PhD

Viral meningitis is the most common form of meningitis, which is inflammation of the tissue that lines the brain and spinal cord. Other causes of meningitis include bacteria, fungi and non-pathogenic triggers of inflammation. The initial phase of the disease is marked by flu-like symptoms, such as fever and body ache. As the disease progresses, characteristic symptoms of headache and stiff neck develop. Most healthy individuals show no symptoms or recover over a few weeks without medical intervention. However, infants and patients with compromised immunity are at greater risk of severe illness. The bacterial form of meningitis is a more serious disease and carries the risk for complications, including brain damage and death.

Causes and Risk Factors

Viral meningitis is caused by a variety of viruses, including enteroviruses, herpesviruses, arboviruses (West Nile virus), measles virus, mumps virus, influenza virus, lymphocytic choriomeningitis virus and human immunodeficiency virus (HIV). The two common causes of viral meningitis in the United States are the following.

  • Enteroviruses: Enteroviruses (e.g., echovirus and coxsackievirus) are the main cause of meningitis in the United States. These viruses live in the digestive tract and reach peak infection numbers during late summer and early fall. Enteroviruses commonly infect children and transmit easily by the hands and mouth through infected droplets.
  • Herpesviruses: Herpesviruses (e.g., herpes simplex viruses and varicella zoster virus) commonly cause meningitis in adolescence and adults. These viruses transmit via contact with infected sores and blisters on the skin. Meningitis is typically associated with herpes simplex virus type 2 (HSV-2), a sexually transmitted virus that causes genital blisters.

The route of transmission varies depending on the virus.

  • Blood: Direct contact with open skin on an infected person allows transmission through blood. This is the most common means of transmission.
  • Air: Inhaling infected droplet in the air allows some viruses to infect new hosts.
  • Stool/vomit: Enteroviruses transmit via contact with vomit or stool from an infected person. Rapid transmission occurs in public swimming pools, childcare centers and other crowded places.
  • Sexual intercourse: Herpesviruses transmit via direct contact with open sores on the genital of an infected person.
  • Mosquito: West Nile virus and other arboviruses transmit through an intermediate host, such as a mosquito. Humans become infected after getting bitten by the insect.
  • Rodents: The lymphocytic choriomeningitis virus spreads via urine, stool or saliva from infected rodents (e.g., pet mice or hamster). Infected droplets can contaminate water, food or dust, which transmit virus when ingested.

Risk factors for viral meningitis include the following:

  • Age: Children younger than age five are at increased risk of viral meningitis. Infants younger than one month old can develop severe meningitis.
  • Poor immunity: Children or adults with a weak immune system due to disease or certain treatments are at greater risk of viral meningitis.

Symptoms

The early symptoms of viral meningitis mimic common flu symptoms. As the inflammation worsens, headache and neck stiffness develop. Some people do not experience any symptoms.

Symptoms in babies:

  • High fever
  • Irritability
  • Sleepiness
  • Poor appetite
  • Bulge on the soft spot on the head (fontanel)
  • Stiff neck or body.

Symptoms in those over the age 2:

  • Headache
  • Nausea and vomiting
  • Stiff neck
  • High fever
  • Confusion
  • Sleepiness
  • Lack of appetite
  • Light sensitivity.

Diagnosis and Treatment

Meningitis is initially diagnosed based on the symptoms, specifically the headache and stiff neck symptoms. Follow-up laboratory testing of naso-oropharyngeal swabs, rectal swabs, stool, cerebrospinal fluid, blood and serum allow for an accurate diagnosis. Imaging techniques (e.g., computerized tomography or magnetic resonance) help detect inflammation in the head and neck region.

Timely diagnosis and treatment of meningitis, in particular bacterial meningitis, is critical; delayed treatment can result in severe complications, including brain damage, hearing loss, impaired memory/learning, seizures and even death. The bacterial form of meningitis requires immediate treatment with antibiotics. There are no known drugs for treating the common viral causes of meningitis; in most cases, patients improve with bed rest and proper intake of fluids. Over-the-counter medication is used to alleviate some of the associated symptoms.

Prevention

Routine vaccination according the guidelines established by the Centers for Disease Control and Prevention (CDC) is the best way to prevent meningitis caused by some viruses (e.g., measles and mumps virus). There is no vaccine against enteroviruses, the most common cause of viral meningitis. Routine handwashing and avoiding contact with sick individuals is the best way to prevent viral meningitis.

Sources

  • “Meningitis”. Mayo Clinic. Retrieved Feb. 12, 2016. http://www.mayoclinic.org/diseases-conditions/meningitis/home/ovc-20169520.
  • “Viral Meningitis”. Centers for Disease Control and Prevention (CDC). Retrieved Feb. 12, 2016. http://www.cdc.gov/meningitis/viral.html.    
  • “Viral Meningitis”. Merck Manuals. Retrieved Feb. 12, 2016. http://www.merckmanuals.com/home/brain,-spinal-cord,-and-nerve-disorders/meningitis/viral-meningitis.
  • “Viral Meningitis”. Meningitis Research Foundation. Retrieved Feb. 12, 2016. http://www.meningitis.org/disease-info/types-causes/viral-meningitis.