The Australian Immunisation Handbook 10th Edition 2013

4.10 MENINGOCOCCAL DISEASE
4.10.1 Bacteriology
Meningococcal disease is caused by the bacterium Neisseria meningitidis (or
meningococcus), a Gram-negative diplococcus. There are 13 known serogroups
distinguished by differences in surface polysaccharides of the outer membrane
capsule. Meningococcal serogroups are designated by letters of the alphabet.
Globally, serogroups A, B, C, W 135 and Y most commonly cause disease.
Meningococci can be further classified by differences in their outer membrane
proteins, which are referred to as serotypes and serosubtypes. 1 More recently,
molecular typing has been used to further differentiate meningococci. There is no
consistent relationship between serogroup or serotype/subtype and virulence. 2
4.10.2 Clinical features
N. meningitidis can cause meningitis, septicaemia or a combination of the two.
Other localised infections, including pneumonia, arthritis and conjunctivitis,
may also occur but are uncommon. Septicaemia, with or without meningitis,
can be particularly severe. The overall mortality risk for invasive disease is high
(between 5 and 10%), despite appropriate antibiotic therapy. 2 Of those who
survive, approximately 10 to 20% develop permanent sequelae, including limb
deformity, skin scarring and neurologic deficits. 1 Prior invasive meningococcal
disease does not induce protective immunity against the implicated serogroup of
meningococci. Therefore, persons with a history of meningococcal disease should
still be vaccinated if required.
N. meningitidis is carried and transmitted only by humans. There are no known
animal reservoirs. Asymptomatic respiratory tract carriage of meningococci
is present in about 10% of the population, and the prevalence may be higher
when groups of people occupy small areas of living space. 3,4 Recent studies
indicate that there may be a number of factors that contribute to the increased
risk of contracting meningococcal disease, including exposure to smokers, recent
illness, living in crowded conditions and multiple intimate kissing partners. 2-4
Persons with inherited disorders of phagocytosis associated with properdin
deficiency or absence of the terminal components of complement, as well
as persons with functional or anatomical asplenia, have an increased risk of
meningococcal infection. 1
The disease is transmitted via droplets and has an incubation period of between
1 and 10 days, but commonly 3 to 4 days. 4 The capacity of meningococcal disease
to have a fulminant and rapidly fatal course in previously healthy (and usually
young) persons causes it to be greatly feared. Intensive public health follow-up
is required after each single case to trace contacts and to institute appropriate
public health measures for them. As a result of all these factors, this disease can
cause widespread community alarm and generate significant media interest. 4
PART 4 VACCINE-PREVENTABLE DISEASES 283
4.10 MENINGOCOCCAL DISEASE