Spinal meningitis develops when a virus, bacterium, fungus, or other trigger causes inflammation of the membranes surrounding the brain and spinal cord. You get it through surprisingly ordinary routes: breathing in respiratory droplets, touching contaminated surfaces, eating certain foods, or, in the case of newborns, passing through the birth canal. Globally, about 2.54 million cases of meningitis occurred in 2023, and the bacterial forms carry a case-fatality rate around 15 to 18 percent.
Viral Meningitis: The Most Common Route
Non-polio enteroviruses cause the majority of viral meningitis cases. These viruses spread through contact with infected feces, saliva, vomit, mucus, or fluid from blisters. In practical terms, that means changing a diaper without washing your hands, sharing utensils, or swallowing water in a contaminated swimming pool can all transmit the virus. In temperate climates, outbreaks peak during summer and early fall, though winter outbreaks do occur.
Viral meningitis is generally less dangerous than bacterial meningitis. Most people recover on their own within a couple of weeks, which is why it sometimes gets dismissed as a bad headache and stiff neck. But the initial symptoms can be indistinguishable from the bacterial form, so any combination of severe headache, neck stiffness, and fever warrants urgent evaluation.
Bacterial Meningitis: How It Spreads
Bacterial meningitis is rarer but far more dangerous. The leading causes in the United States include Streptococcus pneumoniae, Group B Streptococcus, E. coli, Haemophilus influenzae, Neisseria meningitidis, and Listeria monocytogenes. Each of these bacteria reaches you in a slightly different way.
Neisseria meningitidis, the bacterium behind meningococcal disease, spreads through respiratory secretions and saliva. Kissing, coughing near someone, or sharing drinks can transmit it. College campuses and military training facilities have reported outbreaks because young people live in close quarters and share spaces for extended periods. Close household contacts and roommates of an infected person face elevated risk.
Streptococcus pneumoniae also travels via respiratory droplets. It’s the same bacterium responsible for many ear infections and cases of pneumonia, and it can migrate from those initial infections into the bloodstream and eventually to the membranes around the brain. Listeria takes a different path entirely: you ingest it through contaminated food, particularly soft cheeses, deli meats, and occasionally produce like cantaloupe. Pregnant women face a notably higher risk of Listeria infection.
Symptoms of bacterial meningitis can appear within 24 hours of exposure and escalate rapidly, which is what makes it a medical emergency.
How Bacteria Reach the Brain
Getting exposed to one of these bacteria doesn’t automatically mean you’ll develop meningitis. In most cases, the bacteria first colonize the throat, gut, or lungs. From there, they enter the bloodstream. The critical step is what happens next: certain bacteria have surface proteins that let them latch onto and pass through the tightly sealed blood vessels lining the brain. This barrier, known as the blood-brain barrier, normally blocks pathogens from entering the central nervous system. Meningitis-causing bacteria essentially hijack the cells of those blood vessel walls, triggering inflammation and allowing immune cells to flood into the brain’s protective membranes. That flood of immune activity is what produces the swelling, pressure, and damage characteristic of meningitis.
Newborns Face a Unique Risk
Babies can contract meningitis during birth. Group B Streptococcus (GBS) bacteria, which colonize the vaginal or rectal tract of roughly 1 in 4 pregnant women, are the primary concern. Most newborns who develop GBS disease in their first week of life pick up the bacteria while passing through the birth canal. In newborns, GBS commonly causes bloodstream infections, pneumonia, and meningitis. This is why pregnant women are routinely screened for GBS late in pregnancy and given antibiotics during labor if they test positive.
E. coli is another leading cause of meningitis in newborns, transmitted in similar fashion during delivery. Premature infants and those with underdeveloped immune systems are especially vulnerable.
Fungal Meningitis: An Environmental Source
Fungal meningitis works differently from the viral and bacterial forms. You don’t catch it from another person. Instead, you inhale fungal spores from the environment, typically from soil, bird droppings, or decaying organic matter. The spores first infect the lungs, and in people with weakened immune systems, the infection can spread through the bloodstream to the brain and spinal cord.
This form of meningitis almost exclusively affects people with compromised immunity, such as those undergoing organ transplant treatment, living with advanced HIV, or taking long-term immunosuppressive medications. Construction sites, excavation areas, and caves with heavy bat or bird droppings are higher-risk environments. If you’re immunocompromised, avoiding dusty, disturbed soil is a practical precaution.
Non-Infectious Causes
Not all meningitis comes from an infection. Certain medications can trigger inflammation of the meninges on their own. Common anti-inflammatory painkillers like ibuprofen have been documented as a cause, particularly in people with autoimmune conditions such as lupus. Some antibiotics, antiseizure medications, and even intravenous immunoglobulin treatments have been linked to episodes of drug-induced meningitis. Symptoms typically appear within hours of taking the medication and resolve once it’s discontinued.
Autoimmune diseases can also inflame the meninges directly. Lupus is the most frequently cited example. In these cases, the body’s immune system attacks its own tissue rather than responding to an outside pathogen.
Who Is Most at Risk
Age is the strongest predictor. Infants under one year old, teenagers and young adults between 16 and 23, and adults over 65 have the highest rates of meningococcal disease in the United States. The reasons differ by age group: infants have immature immune systems, young adults live in congregate settings, and older adults have declining immune function.
Specific medical conditions raise risk significantly. People missing a functioning spleen, including those with sickle cell disease, lose a key defense against encapsulated bacteria. HIV infection, particularly with a low immune cell count, increases susceptibility. So do rare complement deficiencies, which are gaps in a branch of the immune system that helps clear bacteria from the bloodstream. People taking complement-inhibiting medications face enough added risk that vaccination is required before starting those drugs.
Behavioral and environmental factors matter too. Living in a dormitory or military barracks, traveling to sub-Saharan Africa’s “meningitis belt,” or working as a microbiologist handling live meningitis-causing bacteria all increase exposure. Direct contact with an infected person’s saliva, whether through kissing, sharing food, or being a household member, is the most straightforward route of person-to-person transmission for bacterial forms.
How to Reduce Your Risk
Vaccination is the single most effective protection against bacterial meningitis. Vaccines exist for Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae type b, and Group B Strep (for pregnant women, to protect newborns). The meningococcal vaccine is routinely recommended for preteens at age 11 or 12, with a booster at 16, and is often required for college students living in residence halls.
Beyond vaccination, basic hygiene makes a real difference for viral meningitis: thorough handwashing after using the bathroom or changing diapers, avoiding sharing cups and utensils, and staying out of swimming areas with questionable water quality. For Listeria, pregnant women and immunocompromised individuals benefit from avoiding high-risk foods like unpasteurized soft cheeses and ready-to-eat deli meats. For fungal meningitis, minimizing exposure to dusty or disturbed soil is the most practical step if your immune system is compromised.