Risk Factors

There are several risk factors associated with meningitis. 

• Association with a meningitis case: Although carriage of bacteria that cause meningitis can help to increase natural immunity, close association with a person with meningococcal (or Hib) meningitis is a risk factor for disease.
  
• Age: Meningitis can affect people of any age.  However, infants and children (below 5 years of age) are particularly at risk from meningitis as they have immature immune systems and so are less able to fight infection.  Adolescents and the elderly are also particularly at risk.
  
• Living in a community setting: Situations in which people are living in close proximity to each other, for example students living in university halls of residence, people living in military bases and children in boarding schools and child-care facilities, are at increased risk of meningococcal meningitis.  This is because the organisms that cause meningitis are spread from person to person and are transmitted more easily and more rapidly when people are in living in close proximity to each other.  Disease incidence is highest in the first days after acquisition of carriage.
  
• Compromised immune system: Immunocompromised individuals (such as AIDS patients or patients taking immunosuppressive drugs) and immunodeficient individuals (such as people suffering from leukaemia) are particularly at risk of contracting meningitis as their immune systems are unable to combat the infection effectively.  Infants, who have an immature immune system, and the elderly, whose immune system may be waning, are also particularly at risk.
  
• Tissue damage: Head trauma, such as a skull fracture or injury following neurosurgery, may increase the risk of meningitis by allowing bacteria or viruses entry into the bloodstream or to cross the blood-brain barrier.  Damage to mucosal membranes following illness may also increase the risk of contracting meningitis.
  
• Social factors: social factors such as smoking and close contact with people infected with a causal agent of meningitis may increase the risk of contracting the disease.
  
• International travel: international travel may increase the risk of contracting meningitis, especially to endemic areas, such as the ‘meningitis belt’ (see section on Incidence).