What Causes Meningitis: Facts and Myths

Meningitis may scare you, and it should. Regardless of the underlying trigger, inflammation around your brain and spinal cord can be deadly. Meningitis has many sources, ranging from infectious diseases like germs and viruses to non-infectious ones like trauma or cancer. To avoid spreading erroneous information, you must recognize that several causes exist. This will help you realize that certain kinds can be avoided by vaccination while others cannot.

What causes meningitis?

Meningitis is frightening, and for a good reason. However, being aware of the causes and triggers will enable you to take the preventative measures required in light of your exposure risks.

First, what is meningitis?

Meningitis refers to when the tissues lining the spinal cord and brain become inflamed. Any word ending in -itis signifies the presence of inflammation.

Your brain and spinal cord, protected by fluid and membranes to ensure their safety, are crucial to your existence. These membranes, known as the meninges, might experience different causes of inflammation and infection. Viral (less fatal), bacterial (potentially rapidly fatal), fungal, or parasitic origins can all cause meningitis infections. Meningitis can also develop secondarily to non-infectious illnesses, such as cancer, from certain medications, or from brain/spinal cord trauma.

Symptoms of meningitis

Before exploring the diverse range of meningitis causes, you must be familiar with meningitis symptoms. There are certain often seen indications of meningitis that might raise your suspicions. Symptoms range from mild to severe. Signs may include:

  • Mild to the worst headache of your life
  • Light intolerance (photophobia)
  • Fever
  • Sleepiness
  • Upset stomach, vomiting
  • Stiff neck
  • Balance problems
  • Changes in mental state
  • Purple spots, aka petechiae
  • Agitation, irritability
  • Appetite changes
  • Stroke-like symptoms

Infectious causes of meningitis

Viruses, bacteria, fungi, oh my – A fair number of organisms, some common and some not so common, can cause meningitis.

Bacterial causes

Known bacterial causes of meningitis include:

  • Group B Streptococcus
  • Haemophilus influenzae
  • Listeria monocytogenes
  • Neisseria meningitidis
  • Streptococcus pneumoniae

When referring to bacterial causes of meningitis, medical professionals are most concerned with what they refer to as a meningococcal disease. This is the form of the disease that everyone, understandingly, is petrified of developing. Neisseria meningitidis, like many bacteria, may naturally reside in the back of a person’s throat or nose yet not cause illness.

According to the CDC, 1 out of 10 people possesses this bug in a carrier state, though usually, people remain healthy. However, when the bacteria invade the host, it leads to meningococcal disease.

This organism causes disease worldwide. Generally, six types (serogroups) are recognized - A, B & C; W, X & Y. Illness in the US occurs most frequently from the B, C, or Y subtypes.

While not as contagious as the common cold, COVID, or the flu, it requires close contact for a sustained period with someone shedding and or coughing. Though it can also occur via kissing.

Though no vaccine is ever truly 100% effective, two vaccines licensed for use in the US aid in meningococcal disease prevention. Studies demonstrate effectiveness which ranges from 65% up to 100%, though rates vary with each vaccine. Those used in the US include the Meningococcal conjugate (MenACWY) vaccines and the Serogroup B meningococcal (MenB) vaccines.

While generally fatal without treatment, antibiotics administered promptly, can lead to recovery.

Viral causes

Sadly, an array of viruses may lead to neurologic consequences, including meningitis.

Enteroviruses are a group of viruses common in the US in the summer; for example, one many may be familiar with, Hand, Foot, and Mouth Disease. However, we can also see meningitis occur secondary to measles and mumps, part of the MMR vaccine series recommended for all children. But the MMR vaccine use and effectiveness is a topic for another day.

Additional viruses are also known to induce meningitis, including:

  • Flu (Influenza)
  • Epstein-Barr
  • Herpes simplex viruses
  • Varicella-Zoster virus (chickenpox/shingles)
  • Arboviruses are viruses spread through a mosquito bite or other blood-sucking insects
  • Lymphocytic choriomeningitis virus, though rare, is transmitted by rodents

Two mosquito-borne arboviruses that may be familiar to you, West Nile Virus (WNV) and Eastern equine encephalitis (EEE) virus, are known to cause meningitis.

Fungal causes

People with certain illnesses such as HIV, cancer, or diabetes risk developing fungal meningitis. Exposure occurs via inhalation of spores from the environment. Organisms known to cause fungal disease arising from the natural landscape, usually the soil, include:

  • Blastomyces
  • Coccidioides
  • Cryptococcus
  • Histoplasma

The risk of environmental fungal organisms causing meningitis changes based on your area of residence.

A final fungus known to trigger meningitis is Candidia. This organism normally lives symbiotically (harmlessly) on a person’s skin or within the body. However, it can rarely cause infection by entering the bloodstream or various organs. Generally, this occurs in people with immunosuppressive diseases and babies born prematurely.

Prevention for fungal meningitis doesn’t come in the form of a vaccine. Instead, the CDC recommends avoiding dusty environments such as construction sites, dust storms, yard work, or gardening for those at increased risk. Use air purifiers or other air filtration methods when inside. Clean any wounds well to prevent infection.

Amebic meningitis

Even an organism with a single cell, too small to be seen with the naked eye, called an ameba, can cause meningitis. Naegleria fowleri causes a rare form of amebic meningitis. This organism, which enters the body via the nose, resides in soil and fresh warm water worldwide. Exposure may occur at a variety of locations, from lakes to rivers, hot springs, tap water, soil, and even insufficiently treated water at swimming pools or recreational parks. Most common in the US in Southern states, the organism’s range continues to migrate north with climate change.

Parasitic meningitis

Last but not least, we can see parasites causing meningitis. There are three primary parasites recognized to trigger this disease in people.

  • Angiostrongylus cantonensis, also referred to as neurologic angiostrongyliasis, is transmitted via eating undercooked or raw snails or slugs generally, contaminating a variety of produce.
  • Baylisascaris procyonis, also known as baylisascariasis or neural larva migrans, is a common raccoon parasite rarely found to cause disease in domestic dogs. The parasite’s eggs shed in a raccoon’s feces contaminate the environment, and contact occurs via ingestion, usually of contaminated dirt and soil.
  • Gnathostoma spinigerum, also referred to as neurognathostomiasis, occurs by ingesting raw or insufficiently cooked eels, frogs, poultry, freshwater fish, and even snakes.

Non-infectious causes of meningitis

Non-infectious causes are few but may include some cancers, certain medications, and even trauma to the spine or head. A non-infectious, rare cause of meningitis occurs with drug-induced aseptic meningitis (DIAM). The most common culprits include non-steroidal anti-inflammatory medications (NSAIDs) (e.g., aspirin, naproxen, ibuprofen) and some antibiotics.

Meningitis myths

Myth #1: All forms of meningitis can be prevented with vaccination.

Truth: Vaccines protect against certain forms of meningitis. Too many organisms can cause inflammation of the brain and spinal cord. However, effective vaccines do exist and help protect against several key players. Vaccines against measles, mumps, flu, Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitides may be recommended for you and your family, depending on your exposure risks.

Myth #2: Only the young and old get meningitis.

Truth: Anyone can develop meningitis at any stage of life and at any age.

Myth #3: Viral meningitis only causes mild disease.

Truth: Viral meningitis, generally considered to trigger less severe disease, can still lead to complications and a debilitating illness. While it may not end your life, even once recovered, patients may still experience memory loss or headaches.

Myth #4: Meningitis diagnosis is easy.

Truth: Meningitis may go misdiagnosed early in the course of the disease since several potential causes and symptoms are similar to other illnesses. Additionally, warnings might be hazy. Suppose symptoms of a severe migraine, a stiff neck, or a fever don’t go away immediately. In that case, you must get medical help urgently. Do not wait.

Meningitis awareness saves lives

Meningitis is no laughing matter. Any time spent waiting to receive care might be the difference between life and death. Additionally, learning the facts, awareness of your exposure risks, and recognizing the various causes of meningitis can help safeguard you, your friends, and your family from a possibly fatal yet preventable illness.

Key takeaways

Meningitis, inflammation around the brain and spinal cord, occurs secondary to infectious and non-infectious causes.

While bacterial meningitis can be quickly lethal, viral meningitis often results in a milder condition.

Effective vaccines exist for some forms of meningitis.

Resources:

Archives of Virology. https://doi.org/10.1007/s00705-020-04891-1

Cleaveland Clinic. https://my.clevelandclinic.org/health/articles/14600-meningitis

Cureus. https://pubmed.ncbi.nlm.nih.gov/35295357/

Meningitis Now. https://www.meningitisnow.org/support-us/news-centre/news-stories/top-5-myths-about-meningitis/

National Library of Medicine. Pan American Journal of Public Health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6660876/

Penn Medicine. https://www.pennmedicine.org/for-patients-and-visitors/patient-information/conditions-treated-a-to-z/meningitis

The Centers for Disease Control and Prevention. https://www.cdc.gov/meningococcal/about/causes-transmission.html

The Centers for Disease Control and Prevention. https://www.cdc.gov/vaccines/vpd/mening/hcp/about-vaccine.html

The Centers for Disease Control and Prevention. https://www.cdc.gov/stroke/signs_symptoms.htm

The Centers for Disease Control and Prevention. https://www.cdc.gov/meningitis/non-infectious.html

The Centers for Disease Control and Prevention. https://www.cdc.gov/meningitis/fungal.html

The Centers for Disease Control and Prevention. https://www.cdc.gov/meningitis/clinical-resources.html

The Centers for Disease Control and Prevention. https://www.cdc.gov/meningitis/amebic.html

The Centers for Disease Control and Prevention. https://www.cdc.gov/meningitis/parasitic.html

The National Institute of Health’s National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/meningitis-and-encephalitis-fact-sheet#3083_5

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