Most meningitis is caused by bacteria and viruses that often live in our bodies. Usually these germs stay in the intestines or in the nose and throat, where they may or may not make us sick. But if they spread to the tissues (meninges ) that surround the brain and spinal cord, they cause inflammation. This inflammation is called meningitis.
The germs that can lead to meningitis are contagious, which means they can be passed from one person to another.
Viral meningitis is the most common and the least dangerous. It's caused by viruses, most often enteroviruses that live in the intestines. These viruses can be spread through food, water, or contaminated objects. Meningitis caused by enteroviruses occurs most often in babies and young children.
Bacterial meningitis is caused by bacteria. It is a very serious illness. These germs are usually passed from one person to another through infected saliva or mucus. Most people who get bacterial meningitis get it from one of two types of bacteria:1
In the United States, bacterial meningitis mainly affects adults.2
Other types of bacteria that sometimes cause meningitis are:
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.3
In rare cases, other kinds of bacteria cause meningitis, usually in people with long-term medical conditions. Meningitis also can be caused by other organisms, such as a fungus, and by conditions such as cancer or lupus. Meningitis also can be a complication of an injury (particularly to the skull or face), or brain surgery.