"Why at some point in time the person gets the infection isn't understood," Parker says.
The infection is transmitted by direct contact or respiratory droplets spread when coughing or sneezing. It usually causes an infection that the person doesn't notice, and only in rare cases does it invade the bloodstream, Parker says.
Symptoms include high fever, stiffness and pain in the neck, back and shoulders, nausea and vomiting, severe headache and skin rash. Meningococcal bacteria can cause a variety of illnesses, including pneumonia, septicemia or blood infection, and meningitis, an infection of the covering of the brain and spinal cord.
Meningococcal disease can affect anyone at any age, says Dr. J. Ramsay Farah, a Hagerstown pediatrician specializing in epidemiology.
Children and teenagers are vulnerable because they often are in crowded conditions, Farah says.
Others living in close quarters, such as dormitories and military barracks, also can be affected, Parker says.
Disease caused by N. meningitidis most often occurs in children younger than age 5, according to Maryland Department of Health and Mental Hygiene.
An average of about 3,000 cases of meningococcal disease occur in the United States each year, says Tom Skinner, a spokesman with Centers for Disease Control and Prevention in Atlanta. About 10 to 15 percent of those cases are fatal, Skinner says.
Vaccination isn't routinely given because it is of limited value, Farah says. To be effective, the vaccine would have to be administered every three years, and the cost of an immunization program is too high.
Vaccinations are given to people traveling to foreign countries where the bacteria is known to be prevalent, Farah says.
If a case is diagnosed, preventive medicine is given to those who have had exposure to that person.
State and local health departments in Maryland always are on the lookout for meningococcal disease. Hospitals and laboratories are required by law to report cases. Cases are investigated to determine if there are any links among them.
Twenty-three cases have been reported in Maryland as of April 9 this year, according to Maryland Department of Health and Mental Hygiene.
If symptoms are present, seek medical care as quickly as possible, Parker says.
"If you catch it early enough, it is treatable with doses of antibiotics," he says.