It's important, though, to rule out bacterial causes before determining a course of treatment.
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Aseptic meningitis can cause all the tell-tale symptoms of bacterial meningitis (like severe headache, fever, nausea, vomiting, light-sensitivity, and neck stiffness) but tends to be much less serious. A 2017 review in American Family Physician says it's the most common form of meningitis, affecting about eight out of every 100,000 adults every year.

Like all types of meningitis, aseptic meningitis affects the central nervous system. The disease happens when there's swelling or inflammation in a part of the body called the "meninges," a trio of membranes that cushion the brain and spinal cord.

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Credit: Getty Images / Design by Jo Imperio

A wide range of pathogens and other agents can cause meningitis. Bacterial meningitis, for example, can come from at least 50 kinds of bacteria, says Claire Wright, evidence and policy manager at the UK's Meningitis Research Foundation.

"With bacterial meningitis, if the bacteria enter the bloodstream, they can replicate so rapidly, and they produce toxins that, if you're not given antibiotics very quickly, can [cause you to] rapidly deteriorate, and it can become fatal," Wright tells Health.

When inflammation or swelling of the meninges is caused by something other than bacteria, it falls under the umbrella category of "aseptic meningitis."

Here's what you need to know about aseptic meningitis, including causes, diagnosis, and treatment.

What is aseptic meningitis?

"Meningitis where there's no apparent infection is sometimes called aseptic meningitis, meaning it's not a typical bacterial infection," Paul Auwaerter, MBA, MD, clinical director in the Division of Infectious Diseases at The Johns Hopkins Hospital in Baltimore, tells Health.

Viral meningitis is the most common type of aseptic meningitis. The CDC notes that most viral meningitis cases in the US can be blamed on non-polio enteroviruses, the same bugs that cause seasonal colds, particularly in kids and teens.

In addition to enteroviruses, a range of other viruses can also cause aseptic meningitis, per the CDC, including:

  • Varicella zoster, the virus responsible for causing chickenpox and shingles
  • Influenza virus
  • Measles virus
  • Mumps virus
  • HIV
  • Herpes simplex viruses
  • West Nile virus and other arboviruses
  • Lymphocytic choriomeningitis virus

Though symptoms of aseptic meningitis caused by viruses can be intense, it's usually not a life-threatening disease. "[When] younger adults, teenagers, or children have aseptic meningitis, they're often very sick. They can have headache, fever, nausea, and vomiting," says Dr. Auwaerter. The good news, he adds, is that people in those age groups generally recover without complications.

Viruses aren't the only pathogens to blame for aseptic meningitis. According to the University of Florida Health, aseptic meningitis causes may also include:

  • Fungi
  • Medications (including some over-the-counter pain reducers)
  • Certain diseases (such as cancer, tuberculosis, syphilis, and tick-borne illnesses)
  • Infections close to the brain or spinal cord

"The kinds of organisms that cause meningitis often are very dependent on someone's age, their underlying health condition, whether they've been immunized, and also, at times, certain exposures that can place people at risk," explains Dr. Auwaerter.

According to the CDC, fungal meningitis can occur after a fungal infection spreads to the brain or spinal cord from somewhere else in the body. Wright notes that HIV-positive and immunocompromised individuals tend to be at higher risk for this type of aseptic meningitis. The fungi most commonly associated with the disease are

Aseptic meningitis can also be chemically induced, occurring in response to certain vaccines, including rubella, varicella, rabies, pertussis, and the flu shot. However, a 2018 report in The Clinician's Vaccine Safety Resource Guide notes that routine vaccines used in the US rarely—if ever—cause meningitis, and the benefits of those shots greatly outweigh the risks.

Prolonged use of pain medication, particularly with anti-inflammatory drugs, or NSAIDs, is another potential aseptic meningitis cause. Ibuprofen is the most frequent NSAID that causes aseptic meningitis, according to an older study from 2006 in the journal Medicine. Other medications that can lead to aseptic meningitis include antibiotics, immunosuppressive drugs, and antiepileptic drugs, per a 2014 study in JAMA Internal Medicine.

Lyme disease and other tick- or mosquito-borne infections can be yet another aseptic meningitis cause, hence why a doctor might ask about a patient's recent travels or time spent outdoors, says Marie Grill, MD, specialist in neuroinfectious diseases at the Mayo Clinic.

"We know there's certain infections that are endemic to certain regions. We ask if people have been camping or if there's exposure to insects and whether they're aware of having had any mosquito bites or tick bites," Dr. Grill tells Health.

Aseptic meningitis causes can also include other diseases, such as tuberculosis, and certain parasites. Both are rare causes, but when it comes to meningitis, there are a "broad number of things to consider," says Dr. Grill. "That's why it's so important that we delve into that history," she explains, "so we're as comprehensive as we need to be in determining the cause."

Aseptic meningitis treatment

The treatment for aseptic meningitis depends on the cause. In many cases, doctors will prescribe a course of prophylactic antibiotics when a patient is suspected of having meningitis, until testing and diagnosis can rule out bacterial meningitis.

Patients suspected of having meningitis usually undergo a lumbar puncture, or spinal tap, in which a small amount of cerebrospinal fluid is drawn from the lower back and tested.

"The spinal fluid is our main diagnostic test for being able to discern between bacterial and viral meningitis, or fungal, and the specific cause it is," says Dr. Grill. She adds that things like white blood cell and glucose levels, cultures, and other diagnostics can also offer clues about whether a person has meningitis, and if so, what may be causing it.

"We can do testing for different herpes viruses, we can do testing for enteroviruses, and we can do special antibody testing for things like West Nile virus and other viruses that are carried by mosquitoes that really allows us to be able to confirm the diagnosis," she says.

Other possible tests may include imaging like CT scans or MRIs of the head to look for swelling or inflammation and blood cultures to identify if bacteria are present.

Treating bacterial meningitis should begin immediately and typically involves intravenous antibiotics that can target the specific pathogen causing the infection, per the Mayo Clinic. A doctor may also prescribe corticosteroids to help lower the risk of serious complications.

Aseptic meningitis treatments, on the other hand, aren't always necessary, but it depends on what's behind the infection.

"In terms of viral meningitis, there's no sort of set of treatments," says Wright. "It would just be things like bed rest, taking it easy, and just waiting for the symptoms to subside."

Most people recover from viral meningitis in 10 days or less without treatment, according to the CDC. However, meningitis from the West Nile virus can be more severe and leave patients with lingering fatigue, malaise, and weakness for weeks or months, per the CDC.

If a patient has aseptic meningitis from a fungus, a doctor will typically rely on a long course of high-dose antifungal medications to wipe out the infection. How long a person needs treatment depends on their immune system and the exact fungus that caused the meningitis, according to the CDC.

When aseptic meningitis is caused by a drug, treatment is pretty straightforward: stop taking that medication. This generally clears things up within 24 to 48 hours, according to a 2019 case report and overview of the medical literature published in BMJ Case Reports. In the meantime, supportive care can help keep patients stay comfortable as they recover.

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