Your body's brain and spinal cord are surrounded by three layers of membranes known as the meninges. These protective membranes are vital for providing structural support, cushioning tissue, improving circulation of cerebrospinal fluid and enhancing immune health by providing a defensive barrier against disease.
Meningitis is what happens when the meninges become infected and inflamed, leading to a host of worrisome symptoms that range in seriousness depending on what's causing the infection and inflammation. Some of these symptoms include a high fever, lethargy, hearing loss, kidney failure, confusion, brain damage, learning disabilities, coma and possibly death. "Other symptoms include irritability, unconsciousness, stiff neck, seizures, nausea/vomiting and sensitivity to light," says Dr. John Sellick, a professor of medicine in the infectious diseases division at the University at Buffalo.
Here's why there are such a wide variety of symptoms associated with meningitis and why not every form of meningitis is contagious.
There are multiple types of meningitis, which are typically classified by their cause. These include bacterial, viral, fungal, and parasitic. Viral meningitis is the more common form of the disease but is also generally considered the least dangerous. Viruses such as mumps, West Nile, HIV and the herpes simplex virus can all cause viral meningitis. More commonly though, viral meningitis is caused by a group of viruses known as enteroviruses.
Bacterial meningitis differs from viral meningitis as it's the least common but most dangerous type of meningitis. About one in six people who get it die, and one in five suffer severe complications, per the World Health Organization.
Bacterial meningitis is caused by bacteria entering the bloodstream and traveling to the meninges. Other times, this bacterial can enter the meninges directly due to a head injury or ear or sinus infection.
Fungal meningitis is caused by inhaling fungal spores such as ones found in bird droppings or decaying wood. It can cause death if not treated by antifungal medicine and is especially worrisome in people with compromised immune systems, says Dr. Jatin Vyas, a professor of medicine in the infectious disease division at the Columbia University Vagelos College of Physicians and Surgeons.
Parasitic meningitis can be caused by a tapeworm infection in the brain or by cerebral malaria. Rarely, an amoeba that lives in certain bodies of freshwater can enter the nose and travel to the brain.
Chemicals, allergies, adverse reactions to certain medications and some cancers can also cause meningitis. "Tuberculosis is another cause of meningitis, but tuberculous meningitis is rare in the United States," says Dr. Rodrigo Hasbun, an infectious diseases professor at the University of Texas McGovern Medical School.
Some forms of meningitis are contagious while others are not. Parasitic, fungal and chemical meningitis, for instance, cannot be passed from person to person. Bacterial meningitis can be contagious, but it depends on which bacterial strain has caused the infection. Neisseria meningitidis bacteria, for instance, can not only be transmitted but is so contagious that "in many cases, persons who have been in close contact with patients with Neisseria meningitidis meningitis are given antibiotics to avoid infection," says Vyas.
The most easily transmitted type of the disease is viral meningitis, which can be passed directly from the infected individual when they cough or sneeze or by sharing the same cups or utensils or touching a surface the virus is on, then touching one's eyes, nose or mouth. Fecal-oral transmission can also occur if an infected person doesn't wash their hands and then contaminates surfaces. At the same time, not all forms of viral meningitis are contagious or spread easily. "West Nile Virus is transmitted by mosquito bites and not by human-to-human contact and the herpes simplex virus is only transmitted by unprotected sex," says Hasburn.
It's also worth noting, adds Vyas, that not all the contagious viruses related to meningitis will end up causing meningitis in every person they spread to.
While not all forms of meningitis can be prevented in everyone, certain types can be avoided. Bacterial meningitis, for instance, can be prevented by getting vaccinated against the strains of bacteria that cause the disease. These include the Hib, MenB, MenACWY and PCV15 and PPSV23 vaccines, says Hasbun.
Some forms of viral meningitis can also be avoided by "excellent hand hygiene such as with alcohol hand rubs or hand washing," says Sellick. "Condom use can help you avoid herpes simplex and syphilis transmission," says Hasbun. It's also important to wear repellent when outdoors and to avoid the insects that can spread it, advises Sellick.
"Your healthcare provider can provide specific recommendations about which vaccines you need and how to best avoid meningitis in your area," says Vyas. "And if you develop signs and symptoms of any form of the disease, it's critical to seek prompt medical care."