Meningitis is a disease that can be passed from person to person (contagious). It is caused most often by viruses or bacteria that infect the tissues (meninges) and sometimes the fluid (cerebral spinal fluid, or CSF) that surround the brain and spinal cord.

Viral meningitis

Enteroviruses are the most common cause of viral meningitis. They can live in your intestines without causing illness. But they can cause meningitis when they are passed from one person to another through food, water, or contaminated objects. Meningitis caused by enteroviruses occurs most often in babies and young children.

In rare cases, other viruses, such as human immunodeficiency (HIV) or mumps, may cause meningitis.

Bacterial meningitis

In the United States, bacterial meningitis mainly affects adults.¹ Immunizations continue to help prevent childhood bacterial meningitis. Most people who get bacterial meningitis get it from one of two types of bacteria: Streptococcus pneumoniae or Neisseria meningitidis.²

These bacteria often live in the body, most often in the nose and throat, without causing illness. But the bacteria can cause meningitis if they get into the bloodstream and travel to the cerebrospinal fluid or the tissues (meninges) that surround the brain and spinal cord. These bacteria also can be passed from one person to another, usually through infected saliva or mucus.

Two other bacteria that sometimes cause meningitis are group B streptococci and Listeria monocytogenes. Meningitis caused by group B streptococci bacteria occurs most often in newborns, who can become infected during or after birth. Meningitis caused by Listeria monocytogenes bacteria occurs most often in newborns and in older adults.

The Centers for Disease Control and Prevention (CDC) recommends screening for group B streptococci in all pregnant women at 35 to 37 weeks. Women who have the bacteria are given antibiotics during labor in order to prevent infection in their newborns, and this practice has worked well.³

In rare cases, other bacteria cause meningitis, usually in people with long-term medical conditions.

Meningitis also can be caused by other organisms and conditions. It can be a complication of an illness, an injury (particularly to the skull or face), or brain surgery.

How meningitis is spread

Organisms that cause meningitis can be passed from one person to another or passed from rodents and insects to people. But exposure to an organism that causes meningitis does not mean you will get the infection.

Organisms can be passed from one person to another:

• During birth. A mother can pass organisms that cause meningitis to her baby even if the mother does not have symptoms. Delivering a baby by cesarean section rather than through the birth canal does not always protect the baby from getting the infection. Both bacteria and viruses can be transmitted this way.
• Through stool. Stool could have enteroviruses or certain types of bacteria in it. Washing hands on a regular basis can help prevent you and your children from getting infected this way. More children than adults get meningitis this way.
• Through coughing and sneezing. Infected people can pass certain bacteria that are normally found in saliva or mucus in their noses and throats.
• Through kissing, sexual contact, or contact with infected blood. The human immunodeficiency virus (HIV) also can cause meningitis and can be passed from an infected person to another person through blood or sexual contact but not through kissing.

In rare cases, some organisms that cause meningitis can be passed to people from rodents and insects. The most common of these are arboviruses (including the St. Louis encephalitis and West Nile viruses), which are transmitted through dust and food contaminated by the urine of infected mice, hamsters, and rats.