Meningococcal meningitis is a bacterial form of meningitis, a serious infection of the thin lining that surrounds the brain and spinal cord.

The meningitis belt of sub-Saharan Africa, stretching from Senegal in the west to Ethiopia in the east, has the highest rates of the disease.

In the 2009 epidemic season, 14 African countries implementing enhanced surveillance reported a total of 78 416 suspected cases, including 4053 deaths, the largest number since the 1996 epidemic.

Meningococcal polysaccharide vaccines are available to control the disease.

A new meningococcal conjugate A vaccine developed specifically for Africa should be available by the end of 2010.

Meningococcal meningitis is a bacterial form of meningitis, a serious infection of the meninges that affects the brain membrane. It can cause severe brain damage and is fatal in 50% of cases if untreated.

Several different bacteria can cause meningitis. Neisseria meningitidis is the one with the potential to cause large epidemics. Meningococcal disease was first described in 1805 when an outbreak swept through Geneva, Switzerland. The causative agent, Neisseria meningitidis (the meningococcus) was identified in 1887.

Twelve serogroups of N. meningitidis have been identified, five of which (A, B, C, W135, and X) can cause epidemics. Geographic distribution and epidemic capabilities differ according to the serogroup.

Transmission

The bacteria are transmitted from person to person through droplets of respiratory or throat secretions. Close and prolonged contact – such as kissing, sneezing or coughing on someone, or living in close quarters (such as a dormitory, sharing eating or drinking utensils) with an infected person – facilitates the spread of the disease. The average incubation period is four days, but can range between two and 10 days.

N. meningitidis only infects humans; there is no animal reservoir. The bacteria can be carried in the throat and sometimes, for reasons not fully understood, can overwhelm the body's defenses allowing infection to spread through the bloodstream to the brain. Although there remains gaps in our knowledge, it is believed that 10% to 20% of the population carries N. meningitidis at any given time. However, the carriage rate may be higher in epidemic situations.

Symptoms

The most common symptoms are a stiff neck, high fever, sensitivity to light, confusion, headaches and vomiting. Even when the disease is diagnosed early and adequate treatment is started, 5% to 10% of patients die, typically within 24 to 48 hours after the onset of symptoms. Bacterial meningitis may result in brain damage, hearing loss or a learning disability in 10% to 20% of survivors. A less common but even more severe (often fatal) form of meningococcal disease is meningococcal septicaemia, which is characterized by a hemorrhagic rash and rapid circulatory collapse.

Diagnosis

Initial diagnosis of meningococcal meningitis can be made by clinical examination followed by a lumbar puncture showing a purulent spinal fluid. The bacteria can sometimes be seen in microscopic examinations of the spinal fluid. The diagnosis is supported or confirmed by growing the bacteria from specimens of spinal fluid or blood, by agglutination tests or by polymerase chain reaction (PCR). The identification of the serogroups and susceptibility testing to antibiotics are important to define control measures.

Treatment

Meningococcal disease is potentially fatal and should always be viewed as a medical emergency. Admission to a hospital or health centre is necessary, although isolation of the patient is not necessary. Appropriate antibiotic treatment must be started as soon as possible, ideally after the lumbar puncture has been carried out if such a puncture can be performed immediately. If treatment is started prior to the lumbar puncture it may be difficult to grow the bacteria from the spinal fluid and confirm the diagnosis.

A range of antibiotics can treat the infection, including penicillin, ampicillin, chloramphenicol and ceftriaxone. Under epidemic conditions in Africa in areas with limited health infrastructure and resources, oily chloramphenicol or ceftriaxone are the drugs of choice because a single dose has been shown to be effective on meningococcal meningitis.














 

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