Most cases of meningitis are caused by viruses (viral meningitis) or bacteria (bacterial meningitis). Fungi and other organisms can also cause infectious meningitis. Some cases of meningitis happen after head injuries, certain cancers or other diseases, or reactions to medications.

  Meningitis is inflammation of the meninges, the covering of the brain and spinal cord. It is most often caused by infection (bacterial, viral, or fungal), but can also be produced by chemical irritation, subarachnoid haemorrhage, cancer and other conditions.