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                                Meningitis

                                  Overview

                                  Meningitis is a serious infection of the meninges, the membranes covering the brain and spinal cord. It is a devastating disease and remains a major public health challenge. The disease can be caused by many different pathogens including bacteria, fungi or viruses, but the highest global burden is seen with bacterial meningitis.

                                  Several different bacteria can cause meningitis. Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis are the most frequent ones. N. meningitidis, causing meningococcal meningitis, is the one with the potential to produce large epidemics. There are 12 serogroups of N. meningitidis that have been identified, 6 of which (A, B, C, W, X and Y) can cause epidemics.

                                  Meningococcal meningitis can affect anyone of any age, but mainly affects babies, preschool children and young people. The disease can occur in a range of situations from sporadic cases, small clusters to large epidemics throughout the world, with seasonal variations. Geographic distribution and epidemic potential differ according to serogroup. The largest burden of meningococcal meningitis occurs in the meningitis belt, an area of sub-Saharan Africa, which stretches from Senegal in the west to Ethiopia in the east.

                                  N. meningitidis can cause a variety of diseases. Invasive meningococcal disease (IMD) refers to the range of invasive diseases caused by N. meningitidis, including septicemia, arthritis and meningitis. Similarly, S. pneumoniae causes other invasive diseases including otitis and pneumonia

                                  Transmission

                                  The bacteria that cause meningitis are transmitted from person-to-person through droplets of respiratory or throat secretions from carriers. Close and prolonged contact – such as kissing, sneezing or coughing on someone, or living in close quarters with an infected person, facilitates the spread of the disease. The average incubation period is 4 days but can range between 2 and 10 days.

                                  Neisseria meningitidis only infects humans. The bacteria can be carried in the throat and can sometimes overwhelm the body's defences allowing infection to spread through the bloodstream to the brain. A significant proportion of the population (between 5 and 10%) carries Neisseria meningitidis in their throat at any given time. 

                                   

                                  Symptoms

                                  The most common symptoms of meningitis are a stiff neck, high fever, sensitivity to light, confusion, headaches and vomiting. Even with early diagnosis and adequate treatment, 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 (and often fatal), form of meningococcal disease is meningococcal septicaemia, which is characterized by a haemorrhagic 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 confirmed by growing the bacteria from specimens of spinal fluid or blood, or by polymerase chain reaction (PCR). Diagnosis can also be supported by rapid diagnostic tests such as agglutination tests, although currently available tests have several limitations. The identification of the meningococcal serogroups and testing for susceptibility to antibiotics are important to define control measures. For more guidance on diagnostic methods for meningitis see below: 

                                  Laboratory methods for the diagnosis of meningitis caused by Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae

                                  Laboratory materials for the diagnosis of bacterial meningitis by polymerase chain reaction (PCR). 

                                  For more information on meningitis diagnosis see Our Work - Improving Meningitis Diagnosis

                                   

                                   

                                   

                                  Treatment

                                  Meningococcal disease is potentially fatal and is a medical emergency. Admission to a hospital or health centre is necessary and appropriate antibiotic treatment must be started as soon as possible. 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. However, confirmation of the diagnosis should not delay treatment.

                                  A range of antibiotics can treat the infection, including penicillin, ampicillin and ceftriaxone. Under epidemic conditions in Africa in areas with limited health infrastructure and resources, ceftriaxone is the drug of choice.

                                  Vaccines and immunization

                                  Licensed vaccines against meningococcal disease have been available for more than 40 years. Over time, there have been major improvements in strain coverage and vaccine availability, but to-date, no universal vaccine against meningococcal disease exists. Vaccines are serogroup specific and the protection they confer is of varying duration, dependent on which type is used.

                                  Since 2010, a meningococcal A conjugate vaccine has been rolled out through mass preventive immunization campaigns in the meningitis belt of sub-Saharan Africa, dramatically bringing down cases of the A serogroup.

                                  There are three types of meningococcal vaccines available:

                                  • Polysaccharide vaccines used in outbreak response, mainly in Africa
                                  • Conjugate vaccines used in prevention and outbreak response.
                                  • Protein based vaccine, against N. meningitidis B. It has been introduced into the routine immunization schedule (four countries as of 2020) and used in outbreak response

                                  For more information on meningococcal vaccines and immunization.
                                  For more information on the meningitis ICG vaccine stockpile.

                                  Chemoprophylaxis

                                  Giving antibiotics promptly to close contacts of a person with meningococcal meningitis decreases the risk of transmission.

                                  •  Outside the African meningitis belt, chemoprophylaxis is recommended for close contacts
                                  • In the African meningitis belt, chemoprophylaxis for close contacts is recommended in non-epidemic situations.

                                  Ciprofloxacin antibiotic is the antibiotic of choice, and ceftriaxone an alternative.

                                   

                                   

                                   

                                   

                                  Our work

                                  Serogroup distribution of invasive meningococcal disease, 2019

                                  Neisseria meningitidis bacteria has the potential to cause large-scale epidemics. Twelve types of N. meningitidis, called serogroups, have been identified worldwide, six of which (A, B, C, W, X and Y) can cause devastating epidemics. The distribution and frequency of these serogroups varies from region to region. Monitoring of the circulation of N. meningitidis strains is supported by the WHO Collaborating Centers for meningitis and is essential to detect the emergence of clones with high epidemic potential. Take a look at the maps to find out more about what types of N. meningitidis serogroups and clonal complexes can be found where in the world. 

                                  Publications

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                                  WHO Immunological Basis for Immunization Series: Module 15: meningococcal disease

                                  This module is part of the WHO series The Immunological Basis for Immunization, which was initially developed in 1993 as a set of eight modules, comprising...

                                  Guide to introducing Meningococcal A conjugate vaccine into the routine immunization programme

                                  This guide is for national decision-makers, Expanded Programme on Immunization managers, and immunization partners and stakeholders.Its objectives are:To...