Meningitis is the inflammation of the protective membranes covering the brain
and spinal cord. The inflammation may be caused by infection with viruses and
bacteria but also by fungi, parasites or tumors. It may also result from various
non-infectious causes such as environmental toxins. Meningitis is not always
easy to recognize, and symptoms can be similar to many other more common
illnesses, for example flu.
Most people with viral meningitis will have mild flu-like symptoms. Unlike
bacterial meningitis, viral meningitis does not usually lead to septicaemia
(blood poisoning). Viral meningitis can be caused by several types of viruses,
but by far the most common are enteroviruses. Herpes viruses, the same virus
that can cause cold sores and genital herpes, and West Nile virus, spread by
mosquito bites, have become a cause of many viral meningitis cases.
Bacterial meningitis is not as common as viral meningitis, but it is more
serious. The symptoms usually begin suddenly and rapidly get worse. Meningitis
should be treated as a medical emergency because bacterial meningitis can lead
to septicaemia (blood poisoning), which can be fatal. Most common types of
bacteria that can cause meningitis are:
• Neisseria meningitidis causes meningococcal meningitis, which is a
common form of meningitis in children and young adults. It is highly contagious.
• Haemophilus influenzae. The use of a vaccine has mostly eradicated this
kind of meningitis in countries where it is given to infants.
• Streptococcus pneumonia is the most common cause of bacterial
meningitis in children.
• Listeria monocytogenes is a common form of bacteria. It does not tend
to infect most people, but the very young and very old, as well as pregnant
women, can be at risk.
• Staphylococcus aureus may be found following a head injury or brain
It is important to
perform a lumbar puncture, in which cerebrospinal fluid (CSF) is collected for
testing Tests that may be done include:
• Blood culture.
• Chest x-ray.
• CSF examination for cell count, glucose, and protein.
• Computed tomography scan of the head.
• Gram stain, other special stains, and culture of CSF.