Meningococcal disease is usually transmitted person to person via respiratory droplets from the nose and throat secretions of a person infected with Neisseria meningitidis. A probable diagnosis is defined as a positive antigen test in the cerebrospinal fluid (CSF) or clinical purpura fulminans in the absence of a positive culture. A confirmed case is defined as a clinically compatible case that is laboratory confirmed. All specimens must be obtained from a normally sterile site (e.g. CSF, blood, synovial fluid, pleural fluid or pericardial fluid). The rate of carriage of N.meningitidis in the nasopharynx in the general population is about 10 to 15%.

In 1997, there were 66 confirmed cases and one probable case of meningococcal disease reported. This is comparable to the 63 confirmed and two probable cases reported in 1996.

The incidence of meningococcal disease usually peaks in late winter to early spring. In 1997, disease occurred throughout the year with the lowest incidence in the summer and highest in the late winter (Figure 1).

Figure 1.

Meningococcal disease tends to strike babies, children and young adults. In 1997, the incidence according to age was as shown in Table 1: