Meningitis, a possibly life-threatening disease, is the inflammation of the membranes (menges) and the spinal fluid that surround the brain and the spinal cord. This condition is caused by an infection that travels through the bloodstream to the brain. The most common types of meningitis are caused by a virus, known as viral meningitis, or bacteria, known as bacterial meningitis. Other types of meningitis, fungal meningitis and amoebic meningitis, are rare, but can be serious.
Viral Meningitis
Most cases of meningitis are caused by a viral infection, according to the Mayo Clinic. The most common cause of viral meningitis is enteroviruses, the viruses that commonly cause the stomach flu. Other viruses that may cause viral meningitis include the mumps virus, chicken pox virus, herpes virus and human immunodeficiency virus (HIV). Cases of viral meningitis are usually mild and resolve on their own within a couple of weeks.
Bacterial Meningitis
Meningococcal meningitis, caused by the bacteria Neisseria meningitidis, is responsible for about 3,000 cases of meningitis per year in the United States. Although that number seems low, 10 to 12 percent of those cases are fatal, according to the National Meningitis Association, while 20 percent of those who survive will suffer from permanent damage. Meningococcal meningitis is contagious, according to the Mayo Clinic and is often the cause of meningitis outbreaks on college campuses, in boarding schools or on military bases.
Pneumococcal meningitis, caused by the Streptococcus pneumonia bacteria, is the most common type of bacterial meningitis accounting for 3,000 to 6,000 cases per year according to the National Foundation for Infectious Diseases.
HiB meningitis most commonly affects infants and is caused by the Haemophilus influenzae type B bacteria. Since the introduction of the HiB vaccine in 1986, the number of meningitis cases caused by this bacteria has dropped dramatically.
Tuberculosis, caused by Mycobacterium tuberculosis, is an infection usually found in the lungs. This infection however can travel through the blood stream and result in meningitis. Elderly people with a compromised immune system are most susceptible to this type of meningitis.
Listeria meningitis, caused by the Listeria monocytogenes bacteria, is not common as this type of bacteria found in soils usually only infected infants, pregnant women or the elderly.
Fungal Meningitis
Fungal meningitis is the inflammation of the membranes surrounding the brain and spinal cord caused by an infection by yeast called Cryptococcus neoformans. This yeast is found in the soil and does not usually cause infection in healthy adults. Fungal meningitis is most common in patients suffering from AIDS, according to the Mayo Clinic. Fungal meningitis can be life-threatening.
Amoebic Meningitis
Amoebic meningitis is caused by the microscopic organism Naegleria fowleri which inhabits ponds, lakes, rivers, hot springs and swimming pools that are poorly treated. This type of meningitis is not contagious from person to person, the amoeba is inhaled through the nose while swimming. Although very rare, especially in the United States, this form of meningitis is usually fatal because of the lack of effective treatment, with only three documented cases of survival according to the Centers for Disease Control and Prevention.
