What are risk factors for meningococcemia?
Children and adolescents 5 to 19 years of age are at highest risk for meningococcemia. Newborns acquire antibodies from their mothers via the placenta, although these antibodies fade after a few weeks or months. Toddlers are not immune, and there have been several exposures in day care settings. As children age, they gradually gain immunity to meningococcal strains by coming into contact with milder strains of the bacteria. However, because this immunity is imperfect, it is still possible for adults to get meningococcal disease. In the U.S., medical professionals routinely administer meningococcal vaccine to children in the preteen and teen years.
HIV infection is a risk factor for invasive meningococcal infection. On Aug. 16, 2016, after 24 cases of meningitis arose in men who have sex with men (MSM), two of whom had HIV, California public health officials issued an advisory recommending meningococcal vaccination of all HIV-infected people and MSM who planned to travel to the area. This was the largest meningococcal outbreak in MSM in the U.S.
The complement part of the immune system is critical in fighting off meningococcal disease. Patients who have a history of a specific genetic deficiency in the complement system, or who are taking an anti-complement drug for certain diseases, are at high risk for severe disease. The spleen is necessary for an effective immune response against encapsulated bacteria, so people are at higher risk for fulminant meningococcemia if they have had their spleens taken out (asplenia) or have spleens that function poorly (hyposplenism).
People who have been in close contact with an infected person for a long time are at increased risk to acquire the disease. People who live together in close quarters, such as military barracks or college dormitories, are at special risk for disease because one infected person can spread the disease to many others. One study showed that the attack rate in household contacts was 500 times greater than that of the general population.
In some parts of the world, outbreaks of meningococcal disease occur regularly. This is true of a group of countries in sub-Saharan Africa (the "meningitis belt") where epidemics occur every five to 10 years, with an attack rate of up to 1,000 cases per 100,000 population (compared to up to three per 100,000 population in the rest of the world).
Outbreaks have occurred during the Islamic Hajj pilgrimage. Over 2 million Muslims from over 180 countries visit Saudi Arabia during the Hajj. The pilgrimage is long and arduous. Heat, throat irritation by dust, dense overcrowding, and inadequate hygiene contribute to infection. Saudi Arabia now requires proof of meningococcal (ACWY) vaccination on an International Certificate of Vaccination or Prophylaxis before admitting pilgrims. This has greatly reduced the occurrence of meningitis.