Meningococcal Meningitis

Meningococcal meningitis in short

• an infectious disease caused by the bacterium Neisseria meningitidis (the meningococcus)
• infection may result in meningitis, an infection of the meninges (the lining surrounding the brain and spinal cord)
• epidemics occur sporadically throughout the world, with the highest burden of disease in the "Meningitis Belt" in sub-Saharan Africa
• between 5 and 10% of infected individuals die, even with early and appropriate treatment
• several vaccines are available, but they don’t cover all of the circulating bacterial subtypes

Meningococcal meningitis in detail

Pathogenic agent
Neisseria meningitidis bacteria are gram-negative diplococci. Twelve subtypes – or serogroups – are known; four of them (named A, B, C and W135) are responsible for epidemic outbreaks. The serogroups differ in the composition of their capsular polysaccharides. Between 10 and 25% of the population carry N. meningitidis bacteria without showing clinical symptoms.

Transmission/pathogenesis
Bacteria are transmitted during close contact, usually through droplets of respiratory or throat secretion, e.g. while kissing, sneezing or coughing. The bacteria normally multiply in the pharynx, but they sometimes – for reasons that are not fully understood - enter the bloodstream and are carried through the body to the brain. Humans constitute the only reservoir for N. meningitidis.

Symptoms
The incubation period for meningococcal infections ranges between 2 and 10 days (most often 3–4 days). The symptoms are commonly unspecific, including headaches, fever, shivering or dizziness. About two-thirds of clinical meningococcal infections result in meningitis, an infection of the meninges. The typical symptoms of meningitis are vomiting and a stiff neck. One-third of patients develop meningococcal septicaemia, an even more severe form of the disease; these patients typically show a pronounced petechial exanthema and/or haemorrhagic rash. Between 10 and 15% of sepsis patients suffer from "Waterhouse-Friderichsen-Syndrom", a very severe form of septic shock that is often fatal.

Complications
Between 10 and 20% of individuals with clinical N. meningitidis infection experience complications and severe long-term consequences. Psychosomatic developmental disorders, hydrozephalus, convulsions, intellectual impairments or learning disabilities can occur following meningitis. After meningococcal septicaemia, necrosis of the limbs may occur, that at worst results in amputation.

Treatment
Several antibiotics are effective against N. meningitidis infection. Antimicrobial treatment has to start as soon as possible. Even with adequate treatment, 5–10% of patients die. Patients are no longer contagious 24 h after the start of successful antibiotic treatment.

Epidemiology/incidence
Meningococcal infections occur sporadically throughout the world. In industrialized countries, infections are mainly restricted to isolated cases or small outbreaks (about 0.5 to 1 case/100,000). In temperate regions, the number of cases is highest in winter and spring. According to the Robert Koch Institute in Berlin, 30 to 40% of infections in Europe and North America occur between January and March. These infections are mainly caused by serogroups B and C.

The highest burden of disease is in the sub-Saharan "Meningitis Belt" stretching from Senegal in the west to Ethiopia in the east, where epidemics occur regularly during the dry season between December and June. Major outbreaks in the Meningitis Belt as well as in Asia have been caused in recent years by serogroups A, C, W135 or X.

During major epidemics, 100 to 800 individuals in 100,000 are infected, according to the WHO. Individual communities can experience even higher attack rates. Between 1996 and 2002, a total of 223,000 cases of meningococcal meningitis were reported to the WHO; the most affected countries were Burkina Faso, Chad, Ethiopia and Niger.

Vaccination
Several vaccines to prevent disease are available. Polysaccharide vaccines against serogroups A, C, Y and W135 – those responsible for epidemic outbreaks – exist. These vaccines are not currently recommended by the WHO in routine immunization programs for epidemic control (e.g. in the African Meningitis Belt), as they provide protection for only 3–5 years and cannot be used in children under 2 years of age. However, the national health authorities in many countries recommend immunization against different serogroups.

To know or not to know...
In 1996 Africa experienced the largest outbreak of meningitis in history: Over 250,000 cases were reported, with 25,000 deaths registered.

More information
- WHO: www.who.int/topics/meningitis/en/
- Centers for Disease Control and Prevention: www.cdc.gov/meningitis/bacterial/faqs.htm

Literature
- WHO fact sheet on meningitis: www.who.int/mediacentre/factsheets/fs141/en/
- Robert Koch Institut, Ratgeber Infektionskrankheiten Meningokokken-Erkrankungen: www.rki.de/cln_091/nn_494546/DE/Content/Infekt/EpidBull/Merkblaetter/Ratgeber__Mbl__Meningokokken.html