Meningococcal disease is caused by the Neisseria meningitidis bacterium, of which there are 13 subtypes. Of these, five – A, B, C, W and Y – are responsible for nearly all cases of serious meningococcal infection. Those affected by Men W are usually seriously ill, often requiring a stay in intensive care, and the death rate is higher than is the case for the more common Men B and Men C strains. Meningitis C rates have fallen in the UK since the introduction of the childhood immunisation schedule of a vaccine against the group of bacteria (serogroup) in 1998, and cases of meningitis B are also expected to start to decline following the addition of Men B last September.

The symptoms of bacterial meningitis can include fever, vomiting, drowsiness, confusion, muscle pain, skin rash, headache, stiff neck, photophobia (sensitivity to light) and convulsions or seizures. A baby or young child may refuse to feed, be unresponsive, have an unusual and high-pitched cry and have a bulging fontanelle on the top of their head.

Prompt recognition and hospital treatment are key to making a full recovery, otherwise permanent neurological damage – ranging from minor coordination or learning problems to deadness, paralysis and severe mental impairment – may occur. If septicaemia (blood poisoning) ensues, long-term issues may include scarring, amputation or organ damage.

Meningitis can also be the result of a viral infection. While this is more common than bacterial meningitis, it is also considerably less serious, often being mistaken for a cold or flu. Viral meningitis is more common during the summer months and in children. Meningitis can also result from a fungal infection or exposure to a chemical, although both are extremely rare.