Causes and Risk Factors of Meningitis

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Meningitis is inflammation of the meninges, the tissue that covers and protects the brain and spinal cord. It is usually caused by an infection, but may be caused by cancer, medication or another inflammatory reaction. When meningitis is caused by infection, the infection is usually a bacterial or a viral infection.

Common Causes

The causes of meningitis vary, although the most common causes are bacterial or viral infections.

Other types of infections can occur as well, and they are more likely among people who do not have healthy immune systems, although infectious meningitis can affect anybody. 

Bacterial Infection

There are several types of bacteria that cause meningitis. Each different type of bacteria is more likely to cause meningitis is a certain age group. 

  • Newborns: Group B Streptococcus, Streptococcus pneumoniae, Listeria monocytogenes, Escherichia coli
  • Babies and children: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib), group B Streptococcus
  • Teens and young adults: Neisseria meningitidis, Streptococcus pneumoniae
  • Older Adults: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib), group B Streptococcus, Listeria monocytogenes
  • Tuberculosis meningitis is not necessarily associated with a particular age group, and it is an aggressive type of meningitis that can progress rapidly. 

    Viral Infection

    Viral meningitis can affect people of all ages, but children under the age of 5 and those whose immune systems have been weakened by disease, medication or a transplant are at a higher risk.  Infants younger than one month of age and people with weakened immune systems are also more likely to have a severe case of meningitis when they do get it.

    The most common causes of viral meningitis are:

    • Enterovirus
    • Mumps
    • Measels
    • Influenza virus
    • Herpes simplex virus
    • Varicella zoster- the virus that causes chicken pox

    Fungal and Parasitic Meningitis

    While it is less common than bacterial or viral causes, meningitis can be caused by fungal and parasitic infections, particularly among people who do not have a healthy immune system. 

    Risk Factors for Infectious Meningitis

    It is important to know that, although certain infections can cause meningitis, if you become infected with any of the infectious causes of meningitis, you are not likely to get meningitis, as meningitis is a uncommon complication of infections, not a common effect of most infections. 

    Infectious meningitis is influenced by several factors, including your age, the strength of your immune system, where you have traveled, any surgeries you have had, and if you other recent infections.

    • Age: Certain age groups are at a higher risk of  becoming infected with meningitis. Babies, children, and those who are elderly are more likely to develop a meningitis infection than young or middle aged adults are.
    • Babies, for example, are more likely to get meningitis because they typically have not yet received all vaccinations, and several of the infections that cause meningitis can be prevented with vaccines. 
    • Children are at higher risk of meningitis, often due to the fact that healthy children have recurrent infections at a higher rate than healthy adults. 
    • Elderly adults generally are believed to have weaker immune systems. Elderly adults may also have frequent medical visits  and hospitalizations, which increases exposure to other people who have contagious infections. 
    • Maternal transmission: Maternal to infant transmission can develop if the mother has an infection of the birth canal that could cause meningitis in the newborn child, such as herpes. 
    • Immune Deficiency: People who do not have a healthy immune system are at a higher risk of getting infectious meningitis. An immune deficiency can occur due to immunosuppressant medications, chemotherapy, or any illness that affects the immune system, such as HIV or lupus. 

      Chemical Meningitis

      Meningitis can be caused by an inflammatory reaction to certain medications and procedures. For example, a number of antibiotics and NSAIDs have been associated with aseptic meningitis, meaning meningitis that is not infectious. Some neurosurgical procedures, and even lumbar puncture, can cause aseptic meningitis, although it is very uncommon. 

      Cancer

      Cancer metastasis (spread) from anywhere in the body can travel to the meninges. Cancer cells can invade the meninges and may cause an inflammatory reaction. 

      Autoimmune

      A number of autoimmune disorders, including lupus and sarcoidosis, have been linked to inflammatory meningitis. In these instances, symptoms of meningitis occur and inflammation is present, but there is no identified infectious organism, and the illness may improve with immunosuppressant medications. 

      Lifestyle Risk Factors

      A number of lifestyle risk factors have been identified in association with meningitis. These risk factors make it more likely for a person to become exposed to the infections that cause meningitis. 

      School Setting

      School aged children, young children who go to daycare, and their teachers, are all at risk or meningitis due to their close proximity to one another during the day. Shared utensils and other items can increase the spread of infection.

      Shared Residence

      College student dorm life, which involves sharing living spaces with many other people, increases the risk of meningitis. Similarly, camping groups and sports teams that travel together are also at risk of getting meningitis. 

      Working with Animals

      Zoonotic meningitis affects people who work or play extensively with animals, as well as people who live in areas where the bacteria can be found in animals.

      Sexually Transmitted

      There are several sexually transmitted diseases that can lead to meningitis. For example, advanced syphilis infection can become meningitis. HIV infection, which is sexually transmitted, can suppress the immune system, making it more likely for an infection to become meningitis. 

      Travel

      Traveling may increase your risk for meningococcal disease. Exposure to infectious organisms that you have not ever been exposed to, such as tuberculosis, for example, is more likely if you travel to a region where the infection is more likely. This can put you at an increased risk of developing meningitis. 

      Sources:

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      Turk VE, Šimić I, Makar-Aušperger K, Radačić-Aumiler M. Amoxicillin-induced aseptic meningitis: case report and review of published cases.Int J Clin Pharmacol Ther. 2016 Sep;54(9):716-8. doi: 10.5414/CP202645.