White = 0.9
Nonwhite = 2.3

Females = 1.3
Males = 1.2

Meningococcal disease most commonly manifests as meningitis or meningococcemia. It is transmitted person to person via respiratory droplets from the nose and throat secretions of a person infected with Neisseria meningitidis. Diagnosis in a clinically compatible case is confirmed by isolating meningococci from cerebrospinal fluid (CSF) or blood. A probable diagnosis may be made in the absence of a positive culture if clinical purpura fulminans is present or a gram-stained smear is positive for organisms. All specimens must be obtained from a normally sterile site (e.g. CSF, blood, synovial fluid, and pleural fluid or pericardial fluid). Among the general population, the carriage rate of N. Meningitidis in the nasopharynx is about 10 to 15%.

In 1999, there were 76 confirmed cases of meningococcal disease, which represents a 19% increase over the previous 5-year, mean (64 cases/year) (Figure 1). The increased case reports may have been due to an increased awareness of the disease and the reporting process among health care professionals. Educational information regarding meningococcal disease was distributed to local health departments, doctors, hospital infection control personnel, and clinical laboratory directors via the Indiana Epidemiology Newsletter.

Nonwhites (2.3) were over 2 times more likely to develop invasive meningococcal disease than whites (0.9). The rate of disease among females was 1.3 as compared to 1.2 for men.

The incidence of meningococcal disease usually peaks in late winter to early spring. In 1999, there was a bimodal distribution with an increased number of cases occurring in the spring and the fall (Figure 2).

Meningococcal disease tends to strike babies, children, and young adults. In 1999, incidence was highest for infants (24.5), followed by children under 5 (4.6) (Figure 3).

There are many serogroups of N. meningitidis; and although there is a meningococcal vaccine available in the United States, it offers no protection against serogroup B. The current vaccine is effective against serogroups A, C, Y, and W-135. It is recommended for certain high-risk individuals including: people who have terminal complement component deficiency; people with anatomic or functional asplenia; travelers to or U.S citizens residing in countries in which N. meningitidis is hyperendemic or epidemic; or personnel who are routinely exposed to N. meningitidis in solutions that may be aerosolized. Studies have shown a slightly higher incidence of invasive meningococcal disease in college students living in dormitories, so these individuals may also consider obtaining the vaccine.

The ISDH requests that clinical laboratories submit all positive N. meningitidis isolates collected from a normally sterile site to the ISDH Laboratory for free confirmation and serotyping. Table 1 describes the serotypes of isolates received from 1997-1999.

Only Vanderburgh County (6 cases), Lake County (5 cases) and Marion County (16 cases) reported at least 5 cases in 1999 (Figure 4).