Background:
Meningococcal disease (MD) is a rare condition caused by the bacterium, Neisseria meningitidis, and is transmitted from person to person by the respiratory route. It is estimated that up to 25% of healthy individuals are carriers of the organism and a very small proportion of these persons may ever progress to serious, invasive disease.  There appears to be no relationship between this carriage rate and the rate of disease incidence.^1,2,3,4 Disease may be characterized by multiple signs and symptoms including high fever, severe headache, nucal rigidity, nausea, vomiting, and maculo-papular rash or purpuric lesions. Persons with meningitis may also present with confusion and disorientation. Coma and death may occur in 5-15% of cases.⁵

Nationwide, rates of MD remain highest among infants, but between 1990-2000, rates of disease rose increasingly among adolescents and young adults.⁶  Cases of MD occur throughout the year, but a seasonality of the disease is recognized, with rates commonly being highest during winter months (December-February), and lowest during summer months (June-August).  MD cases most frequently occur sporadically, without apparent connections between cases.  Outbreaks describe <3% of all cases in the United States.⁷ 

During the 1990's the annual crude rate of MD across the United States remained at or near 1 case per 100,000 population (1.0/100,000).  In Texas, the crude rate climbed gradually during the decade from 0.5 to 1.4 cases per 100,000 population, with part of this increase being accounted for by outbreaks in Gregg County, in the north-east part of the state, in 1994 and 1995.⁸ 

In cases of sporadic disease, the management of close contacts (i.e. household members, day care center contacts, and others with potential direct exposure to the case's respiratory secretions) is by antimicrobial chemoprophylaxis with either rifampin, ciprofloxacin, or ceftriaxone. Outbreaks of MD are defined by the identification of >3 confirmed cases of same-serogroup infection in a well-defined population during a three-month period with a resulting primary attack rate of >10 cases per 100,000 population.⁹  When epidemiological evidence suggests that such an outbreak is caused by a vaccine-preventable serogroup (A,C,Y, W-135), vaccination of all persons at risk should be considered.^10,11   Vaccination for MD is not routine in the United States except among groups specifically identified as being at higher risk for disease (i.e, military personnel, college students, travelers to endemic areas). Vaccination is not otherwise recommended as a control or prevention measure among the general population when disease incidence is lower than 10.0/100,000.
 
Epidemiology of Meningococcal disease in Houston
In Houston, the crude rate of MD between 1990-2000 was generally lower than, but parallel to the climb seen in Texas and in the United States, with a gradual rise from 0.4 to 1.1 cases per 100,000 residents.  Surveillance data compiled by the Bureau of Epidemiology indicate that approximately 14 cases are expected to occur every year in the city, with an average of 1-2 being diagnosed and reported each month. 

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