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What Is Meningitis? Symptoms, Diagnosis, Treatment, and Prevention

Meningitis occurs when there is an inflammation of the membranes that cover and protect the brain and spinal cord (the meninges), according to the Centers for Disease Control and Prevention (CDC). (1)

Viral infections are the most common cause of meningitis in the United States, but the illness can also be caused by bacterial, parasitic, and fungal infections. (2) Other types of infections can also cause meningitis, and there are noninfectious causes as well, such as injuries, cancer, autoimmune conditions, and certain medications. (1)

Viral meningitis, the most common type of meningitis, is typically mild and frequently goes away on its own. (2) However, bacterial meningitis can lead to permanent brain damage and be life-threatening within days if it’s not treated, so be sure to seek medical care immediately if you think you may have the infection.

Early meningitis symptoms may seem like flu symptoms and may present over several hours or several days. (2)

Different types of meningitis have different causes.

Causes of Viral Meningitis

In the United States, viral meningitis is typically caused by enteroviruses, a group of viruses that are most common in late summer and early fall. (2) However, few people infected with enteroviruses actually develop meningitis. (3)

Other viruses, including herpes simplex virus, HIV, mumps, and West Nile virus, can also cause viral meningitis. (2)

Causes of Bacterial Meningitis

Various types of bacteria can cause bacterial meningitis. (4) In the United States, the main causes of bacterial meningitis are:

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

The germs that cause bacterial meningitis typically spread from person to person, but certain germs, such as Listeria monocytogenes, are usually acquired through contaminated food.

Bacterial meningitis is very serious and can be fatal. Although most people recover, permanent complications may include brain damage, hearing loss, and learning disabilities. If you have meningitis symptoms, be sure to see a doctor right away, as prompt treatment is critical.

Causes of Fungal Meningitis

Fungal meningitis can occur after a fungus spreads from part of the body to the brain or spinal cord. (5)

Some causes of fungal meningitis include:

  • Cryptococcus, which lives in soil, on decaying wood, and in bird droppings
  • Histoplasma, which lives in environments with large amounts of bird or bat droppings
  • Blastomyces, which lives in moist soil and in decaying wood and leaves
  • Coccidioides, which lives in the soil in the southwestern United States and areas of Central and South America
  • Candida, which normally lives inside the body and on the skin without causing any issues but can cause an infection in people who are high risk

Fungal meningitis doesn’t spread between people, so it’s not contagious, and it’s rare in the United States. People with weakened immune systems are at increased risk, such as those who have HIV and cancer, or those who take certain medications. Premature babies with very low birth weights also have a greater risk of getting a Candida bloodstream infection.

Causes of Parasitic Meningitis

Certain parasites can cause a rare type of meningitis called eosinophilic meningitis, eosinophilic meningoencephalitis, or EM. (6)

The top three parasites that can cause EM are:

  • Angiostrongylus cantonensis
  • Baylisascaris procyonis
  • Gnathostoma spinigerum

When people get infected with parasitic meningitis, it’s usually because they’ve ingested infected animals or contaminated foods. Examples include raw or undercooked snails or slugs, contaminated produce, parasite eggs found in raccoon feces or dirt, or raw or undercooked freshwater fish or eels, frogs, poultry, or snakes.

Causes of Amebic Meningitis

Primary amebic meningoencephalitis (PAM), a rare brain infection that is deadly in most cases, is caused by the amoeba Naegleria fowleri. (7)

Naegleria fowleri can be found in:

  • Warm fresh water, such as lakes and rivers
  • Geothermal (naturally hot) water, such as hot springs
  • Warm water discharge from industrial plants
  • Untreated geothermal drinking water sources
  • Poorly maintained swimming pools
  • Water heaters
  • Soil

Very rarely, Naegleria infections can be caused by contaminated water getting in the nose. For example, this can occur when people submerge their heads in water or cleanse their noses during religious practices, or irrigate their sinuses using contaminated tap water. But most cases in the United States have been linked to swimming in Southern states like Florida and Texas.

Causes of Noninfectious Meningitis

Causes of noninfectious meningitis (meningitis that is not caused by a microorganism) include: (8)

  • Cancer
  • Lupus
  • Some medication
  • Head injury
  • Brain surgery

Risk Factors

There are several factors that can increase your risk of getting meningitis, including: (2)

  • Skipping vaccinations.
  • Being young: Viral meningitis usually occurs in children under age 5. Bacterial meningitis is common in people younger than age 20.
  • Living in a community setting, such as a college dorm, military base, or boarding school.
  • Being pregnant. Meningitis can be caused by listeriosis, an infection caused by Listeria bacteria, and pregnancy increases the risk of listeriosis.
  • Having a compromised immune system, which can be due to factors including AIDS, alcoholism, diabetes, and taking immunosuppressant drugs.
  • Having your spleen removed.

Doctors diagnose meningitis by taking a medical history, conducting a physical exam, and administering diagnostic tests. (9) Your healthcare provider may look for signs of infection around the head, ears, throat, and skin along the spine.

Tests used to diagnose meningitis include:

  • Blood Cultures Blood cultures may be ordered to detect bacteria.
  • Computerized Tomography (CT) or Magnetic Resonance Imaging (MRI) CT or MRI scans of the head may reveal swelling or inflammation, and X-rays or CT scans of the chest or sinuses may also show infection.
  • Spinal Tap A spinal tap (lumbar puncture) is done to collect cerebrospinal fluid (CSF) and definitively diagnose meningitis. If you have meningitis, the CSF frequently shows an elevated white blood cell count and increased protein.
  • CSF Analysis CSF culture analysis may be done to pinpoint which bacteria or fungi caused the meningitis. In cases of viral meningitis, your doctor may order a DNA-based test known as a polymerase chain reaction (PCR) amplification or a test to check for antibodies against certain viruses.

Prognosis of Meningitis

Some cases of meningitis get better without treatment in a few weeks. In other cases, emergency treatment is necessary to prevent serious complications, including death. (2)

Viral meningitis is typically mild and frequently goes away on its own.

Early diagnosis and treatment of bacterial meningitis are critical to prevent permanent neurological damage. (10)

In most cases, people with very mild meningitis can make a full recovery. (11)

Viral meningitis symptoms should go away within two weeks, and lasting complications are unlikely. (10)

People who have bacterial meningitis generally show some improvement 48–72 hours after treatment but are more likely to experience complications. (11)

Treatment for Bacterial Meningitis

Acute bacterial meningitis is a medical emergency that must be treated right away, even before results of the CSF analysis are known. (9)

Medication Options

Medication for bacterial meningitis may include:

  • Intravenous antibiotics
  • Corticosteroids to reduce inflammation

Your doctor may also drain any infected sinuses or mastoids, which are the bones behind the outer ear that connect to the middle ear.

Treatment for Viral Meningitis

Antibiotics can’t cure viral meningitis. For mild cases, treatment usually includes bed rest and lots of fluids.

Medication Options

Medication options for viral meningitis include:

  • Over-the-counter pain medication (for fever and body aches)
  • Corticosteroids to reduce swelling in the brain
  • Anticonvulsant medication to control seizures
  • Antiviral medication, if a herpesvirus caused your meningitis

Treatment for Other Types of Meningitis

There are various treatments for other types of meningitis, including

  • Antifungal medication to treat fungal meningitis
  • Corticosteroids to treat noninfectious meningitis

Learn More About Treatment for Meningitis: Medication, Alternative and Complementary Therapies, Surgery Options, and More

Prevention of Meningitis

The following steps can help prevent meningitis: (2)

  • Wash your hands well and teach children to do the same.
  • Don’t share drinks, foods, straws, eating utensils, lip balms, or toothbrushes with other people.
  • Stay healthy and boost your immune system by getting enough rest, exercising regularly, and eating a healthy diet with plenty of fresh fruit, vegetables, and whole grains.
  • When you need to cough or sneeze, cover your mouth and nose.
  • If you’re pregnant, reduce your risk of listeriosis by cooking meat, including hot dogs and deli meat, to 165 degrees F. Avoid cheeses made from unpasteurized milk, and eat only cheeses made with pasteurized milk.

Vaccines for Meningitis

You can prevent bacterial meningitis by keeping yourself and your children up-to-date on the following vaccines:

  • Haemophilus Influenzae Type B (Hib) Vaccine Children in the United States routinely receive this vaccine starting at about 2 months old. It’s also recommended for some adults, including people who have sickle cell disease or AIDS and individuals who don’t have a spleen.
  • Pneumococcal Conjugate Vaccine (PCV13) This vaccine is routinely given to American children younger than 2 years old. Additional doses are recommended for children older than 2 years old and younger than 5 years old who are at increased risk of pneumococcal disease, such as those who have chronic heart or lung disease or cancer. A different version of the vaccine (PCV15 and/or PCV20) is recommended for adults and those with immunocompromising conditions who have not yet gotten a pneumococcal conjugate vaccine.
  • Pneumococcal Polysaccharide Vaccine (PPSV23) This vaccine may be recommended for older children and adults who need protection from pneumococcal bacteria, including all adults older than 65; younger adults and children age 2 and older who have weak immune systems or illnesses such as heart disease, diabetes, or sickle cell anemia; and anyone who doesn’t have a spleen.
  • Meningococcal Conjugate Vaccine The CDC recommends that children receive a single dose of this vaccine at age 11 or 12, and a booster shot at age 16. It can also be given to children between 2 months old and 10 years old who are at increased risk of bacterial meningitis, adults with underlying immunocompromising conditions (such as HIV), and unvaccinated people who have been exposed in outbreaks.

Early treatment is key to preventing complications from meningitis. However, if treatment is delayed, serious complications can occur, such as: (2)

  • Hearing loss
  • Memory problems
  • Learning disabilities
  • Brain damage
  • Gait problems
  • Seizures
  • Kidney failure
  • Shock
  • Death

At least 1.2 million cases of bacterial meningitis are estimated to occur worldwide each year, according to the World Health Organization. (12)

While enteroviruses cause most cases of viral meningitis and most people are exposed to these viruses, fewer than 1 in every 1,000 people infected with enteroviruses actually develops meningitis. (13)

The highest incidence of meningococcal disease, which can cause meningitis, is found in the “meningitis belt” of sub-Saharan Africa, according to the CDC. (14) Here, major epidemics occur every 5 to 12 years, with attack rates reaching 1,000 cases per 100,000 population.

While the outbreaks are not fully understood, the following characteristics of the region may play a role:

  • Dry and dusty conditions during the dry season, from December to June
  • Immunological susceptibility of the population
  • Travel and large population displacements
  • Crowded living conditions

Encephalitis

Encephalitis is inflammation of the brain, as opposed to meningitis, which is inflammation of the membranes that surround the brain and spinal cord. (10) The illness is usually caused by a viral infection. In most cases, people with encephalitis can make a full recovery.

Septicemia

The same bacteria that cause bacterial meningitis can also be associated with sepsis, or septicemia, which is the medical term for a bacterial infection that spreads throughout the body in the bloodstream. (4) Sepsis is the body’s extreme response to an infection, and it can be fatal without prompt treatment. (15)

RELATED: What Is Sepsis? Symptoms, Causes, Diagnosis, Treatment, and Prevention

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