Meningitis

Overview
Meningitis
Encephalitis
Signs, Symptoms and Treatment
Tests
Prevention
Treatment
FAQs

Meningitis
Most cases of meningitis are due to a bacterial or viral infection. The infection may be primary – starting in the meninges, or secondary – spreading from an infection in another part of the body. Viral meningitis is the most common form of meningitis in England with approximately 3,000 cases of viral meningitis reported in England and Wales every year, according to National Institute of Neurological Disorders and Stroke (NINDS). It is usually mild to moderate in severity and self-limited. Viral meningitis is frequently caused by an enterovirus or herpes virus but may also be caused by arboviruses (see Encephalitis).

Bacterial meningitis is a medical emergency. Cases can arise suddenly, with symptoms worsening within hours to a couple of days. Rapid identification and treatment is crucial. Untreated bacterial meningitis is usually fatal. While this condition can be caused by many different types (species) of bacteria, the most common causes are:

Streptococcus pneumoniae – called pneumococcal meningitis. Infants under 2 years old and those with compromised immune systems are at greatest risk for it. A pneumococcal vaccine is now given as part of the routine immunisation programme in the UK. It protects against some forms of pneumococcal meningitis
Neisseria meningitidis – called meningococcal meningitis. Seen in college students, infants, children, international travelers, and the immune-compromised. It is the leading cause of bacterial meningitis in children and young adults and is highly contagious. However, since the introduction of a meningitis C vaccine many cases have been prevented.
Haemophilus influenzae type b – once the most common cause of bacterial meningitis, its incidence has decreased because of widespread vaccination of children.
Group B streptococcus, Escherichia coli, and Listeria monocytogenes are the most common causes of meningitis in the neonate (babies less six weeks old) and may be passed from the mother to her baby.

Chronic meningitis is meningitis that last for more than 4 weeks. It may be caused by bacteria such as Mycobacterium tuberculosis, which causes tuberculosis, by Treponema pallidum, which causes syphilis, and by fungi. Fungal meningitis is most commonly seen in immune compromised patients, such as those with HIV/AIDS, but may affect anyone. The most common cause is Cryptococcus neoformans (cryptococcal meningitis), found in dirt and bird droppings. Other causes include Coccidioides immitis, Histoplasma capsulatum, and Candida species.

Amoebic meningitis is rare and can be lethal. It is caused by the free-living amoeba, Naegleria fowleri, a single-cell parasite, which can be found in warm water lakes and rivers.