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Fact Sheets

Meningococcal Meningitis

Meningococcal meningitis is caused by the bacterium, Neisseria meningitidis. It ioccurs throughout the world.. In temperate climates most countries show a steady number of sporadic cases or small clusters with seasonal increase in the winter period. A different pattern, with epidemics recurring during 2-3 consecutive years has also been observed, for example India & Nepal in the mid-1980s & Mongolia in 1994-1995. The largest epidemics of meningococcal meningitis have been reported in sub-Saharan African countries within the meningitis belt (which extends from Ethiopia in the east to Senegal in the west, mainly within the range of 300 mm annual rainfall) but epidemic meningococcal disease can occur in any country regardless of climate. Epidemics occur in the winter-spring period in temperate zones & in the dry season in tropical countries. The highest rates occur in young children but, especially during epidemics, older children, teenagers & young adults are also affected.

The Causative Agent:

Neisseria meningitides is a Gram-negative coccal bacterium occurring as a number of sub- or serogroups. Serogroup A & C meningococci have been the main causes of epidemic meningitis. Serogroup B, generally associated with sporadic disease, may cause some upsurges or outbreaks, Serogroups W135 and Y have been responsible for outbreaks in sub-Saharan Africa and Europe. These have previously been associated with travellers to Saudi Arabia on Haj - strict vaccination procedures have reduced this risk to substantially nil.

How the disease is transmitted:

Transmission is by direct close contact including respiratory droplets from nose & throat of infected persons i.e sneezing and coughing. Most infections do not actually produce disease but infected persons may then become symptomless carriers. Waning immunity in the population against a particular strain favours epidemics, as do overcrowding, smoking and climatic conditions such as dry season or prolonged drought & dust storms. Concomitant viral upper respiratory tract infections may also contribute to the development of epidemics.

The disease:

The time from infection to symptoms of the disease is usually 3-4 days but can be as short as 48 hours or as long as 10 days. The illness is characterized by sudden onset of intense headache, fever, nausea, vomiting, dread of bright light (photophobia) and stiff neck. Drowsiness and lethargy proceeding to delirium, coma and/or convulsions may occur. Infants may have illness without a stiff neck, so high fever and excessive drowsiness should give rise to suspicion of meningococcal infection. Given early diagnosis and adequate antibiotic therapy the death rate may be anything from 5 - 15 % but may exceed 50% in the absence of treatment. A less common but more severe (often fatal) form of meningococcal disease is meningococcal septicaemia characterised by sudden fever associated with shock and bleeding into the skin. Diagnosis is confirmed with specialized laboratory tests of cerebrospinal fluid & blood.

Prevention:

Since the disease is spread by direct contact with or droplet infection from an infected patient standard hygiene procedures may help reduce the chances of becoming infected, but in an epidemic infection can occur easily in crowded places. Chemoprophylaxis with the use of antibiotics is usually advised for people in close contact with patients in the endemic situation. It is not an effective means of interrupting transmission during an epidemic. Vaccination is the most effective means of prevention.

Vaccines available:

From December 2010 a new vaccine has become available. Essentially there have been are two types of vaccine used, under different trade names - "polysaccharide" vaccines with a short (2 - 3 year) effectiveness, and "conjugate" vaccines which provide more prolonged (10 years) protection. The vaccine provide by Australian governments currently for infants and adolescents is a conjugate long-acting vaccine but is monovalent i.e. only effective against the meningococcal serogroup C which is a common cause of sporadic disease.

Until December 2010 the only vaccine effective against A,C, W135 and Y serogroups (quadrivalent) available in Australia has been a polysaccharide vaccine i.e short-acting one, but nevertheless useful for travellers to countries where more than one serogroup predominates. However, the conjugate i.e long-acting, quadrivalent vaccine is now available and should be the vaccine of choice for travellers replacing the short-acting vaccine previously used. Whether it is used locally depends on personal choice and future government policy.