The following is an overview of meningitis around the world and in particular, sub-Saharan Africa. Those health professionals interested in learning more about the diagnosis of meningitis are invited to download this document from the CDC. This 95-page document contains in-depth information on the laboratory diagnosis of meningitis. It is informative and an excellent manual to have on hand.
PDF Download : Laboratory Methods for the Diagnosis of Meningitis
Meningococcal meningitis occurs globally. The disease is endemic in temperate climates
causing a steady number of sporadic cases or small clusters with a seasonal increase in
winter and spring. A different pattern, with epidemics flaring for two to three
consecutive years, has been observed in countries in sub-Saharan Africa. This area has
experienced epidemic cycles every eight to 12 years in the past, and the intervals between
major epidemics have become shorter and more irregular since the beginning of the 1980s.
The most recent meningococcal meningitis pandemic, which began in 1996, has so far
resulted in approximately 300,000 cases being reported to the World Health Organization.
The most affected countries have been Nigeria, Burkina Faso, Mali and Niger and the Sudan. In 1998, the
outbreaks occurring in Chad and Cameroon accounted for about 30% of the total cases
reported in that year. By the year 2000, the pandemic area had shifted to the Sudan with nearly 4,000 cases reported thus far.
Most recently, pilgrims returning from Mecca spread the disease throughout the world. Over 300 cases of a rare strain of the disease were recorded with 72 known deaths.
Epidemiology: Apart from epidemics, at least 1.2 million cases of bacterial
meningitis are estimated to occur every year;135,000 of them are fatal. Approximately
500,000 of these cases and 50,000 of the deaths are due to meningococcus. Meningococcal
meningitis is the only form of bacterial meningitis which causes epidemics. The largest
epidemics of meningococcal meningitis are experienced by sub-Saharan African countries
within the so called "meningitis belt" which extends from Ethiopia in the east
to Senegal in the west. Epidemics occur in the dry season in this area. While the highest
disease rates are found in young children, during epidemics older children, teenagers and
young adults are also affected.
A large widespread epidemic can follow on from a localised outbreak the previous year
and incidence rates remain elevated during the following 1-2 years unless the appropriate
control measures including mass immunisation are instituted.
Etiological (i.e., causal) agent: Neisseria meningitidis, a Gram-negative
bacterium. Serogroup A and C meningococci are the main causes of epidemic meningitis.
Serogroup B, generally associated with sporadic disease, may cause some upsurges or
Transmission: Transmission is by direct contact, including respiratory droplets
from nose and throat of infected persons. Most infections are subclinical and many
infected people become symptomless carriers. Waning immunity among the population against
a particular strain favours epidemics, as do overcrowding and climatic conditions such as
dry season or prolonged drought and dust storms. Upper respiratory tract infections may
also contribute to the development of epidemics.
Incubation period: Two to 10 days, often three to four days.
Clinical picture: Meningococcal meningitis is characterized by sudden onset of
intense headache, fever, nausea, vomiting, photophobia, and stiff neck. Neurological signs
include lethargy, delirium, coma and/or convulsions. Infants may have illness without
sudden onset and stiff neck. Even when the disease is diagnosed early and adequate therapy
instituted, the case fatality rate is between 5% and 10% and may exceed 50% in the absence
of treatment. In addition to the mortality associated with meningococcal meningitis 15%
and 20% of those who survive will suffer with neurological sequelae (e.g. deafness, mental
retardation) as a result of their illness. A less common but more severe (often fatal)
form of meningococcal disease is meningococcal septicaemia which is characterised by rapid
circulatory collapse and a haemorrhagic rash.
Diagnosis: Laboratory examination of the cerebrospinal fluid will usually
confirm the presence of a bacterial meningitis. More specialized laboratory tests, which
may include culture of cerebrospinal fluid and blood specimens, are needed for
identification of Neisseria meningitidis and the serogroup as well as its
susceptibility to antibiotics.
Therapy: Meningococcal disease is potentially fatal and should always be viewed
as a medical emergency. Admission to a hospital or health centre is necessary.
Antimicrobial therapy must be instituted as soon as possible after the lumbar puncture has
been carried out. However, isolation of the patient is not necessary. A range of drugs may
be used depending on antibiotic susceptibility: penicillin G, ampicillin; chloramphenicol,
ceftriaxone. Oily chloramphenicol may be the drug of choice in areas with limited health
facilities because a single dose of the long-acting form has been shown to be effective.
Control: Epidemics usually spread rapidly to a peak within weeks but may last
for several months in the absence of vaccination. Polysaccharide vaccines are available
against serogroups A, C, Y, W135. A mass immunisation campaign that reaches at least 80%
of the entire population with serogroup A & C vaccine can halt an epidemic due to
meningococcae of these serogroups.
Prevention: Chemoprophylaxis can be considered for people in close contact with
patients in the endemic situation. It is not an effective means of interrupting
transmission during an epidemic. Potential antimicrobials for chemoprophylaxis are
rifampicin, mynocycline, spiramycin, ciprofloxacin and ceftriaxone. In some countries,
vaccination is used for close contacts of patients with meningococcal disease due to
A,C,Y, or W135 serogroups to prevent secondary cases.
Advice for travellers: Travellers to areas affected by meningococcal outbreaks
are advised to be vaccinated.
The number of cases of cerebrospinal meningitis (the majority of which will be
meningococcal disease) reported from selected countries in the "African meningitis
belt" is shown for years since 1977 in Figure 1. The periodic nature of the epidemics
is demonstrated and the shortened inter-epidemic interval observed in recent decades is
seen in the case of Niger. Both Sudan and Ethiopia have experienced large epidemics in the 80s and by 1998 had not experienced an increase in cases. Starting in late 1999 however, this changed. Sudan has recently asked for $1 million in aid to fight meningitis having been caught off guard by the virulence of the epidemic in that country.
Figure1. Numbers of cases of
meningococcal meningitis reported to WHO from selected countries of "African
Meningitis Belt" 1997 to 1998