Ideally, meningitis should be diagnosed by a microscope examination of fluid taken from a patient during a lumbar puncture, which means inserting a needle into the spinal canal low on the back.

During an outbreak, however, there is no time to do this on every suspected patient and MSF teams use a clinical case definition: high fever and at least three if the following signs - neck stiffness, headache, vomiting, convulsions, coma or a meningococcal rash.

This rash is easily recognised - it looks like bleeding into the skin and is a harbinger of death. In a hospital setting, when only sporadic cases of meningitis must be dealt with, doctors can treat each patient with a regimen of intravenous antibiotics, giving large doses of one or sometimes two drugs several times a day.

During a major epidemic, however, it is essential to find more rapid ways of dealing with perhaps several hundred cases each day. The method that has been tested and proven by MSF teams is to use an oily suspension of chloramphenicol, which is an antibiotic that had largely gone out of favour until applied to this particular use.

Suspension in an oily base gives the drug a long duration of action, so that it can be administered via a single intramuscular injection and still be active 24 hours or more later. For many patients a single injection is sufficient to effect cure. Such a regimen has obvious advantages in a remote rural setting where large numbers of people spread over a wide area must be treated.