"We drove out of the compound early each morning to go and vaccinate in the villages. The little girl next door would wave till we disappeared round the corner. One morning she waved and grinned as usual but by the time we got home that evening she was near death." - MSF field doctor, Sudan Meningitis is an infection of the meninges, which is the membrane that covers the brain and spinal cord like a sheath. It can be caused by a variety of germs, both viral and bacterial. The most dangerous form, however, is caused by the bacterium Neisseria meningitidis, commonly called the meningococcus. This germ is serious both because it is highly virulent for the individuals it affects and because unlike most other causes of meningitis it has the potential to cause epidemics. Meningococcal meningitis occurs in two distinct patterns, endemic and epidemic. In most countries of the world there are sporadic cases from time to time, which means that the meningococcus germ is endemic there at low levels. However there is an area that spans sub-Saharan Africa called the meningitis belt where large epidemics occur regularly, affecting many thousands of people. Such an occurrence usually requires the intervention of specialised teams such as those of MSF.