Meningitis

There are many different bacteria and viruses that can cause meningitis. In most instances, it is more common for these viruses or bacteria to cause some other illness, such as an ear infection, pneumonia or other illness. It is not known why one individual develops meningitis when others exposed to the same virus or bacteria don't get as sick, or don't get sick at all.

Bacterial Meningitis

Some forms of meningitis may pose a risk for causing serious illness among close contacts. These include meningococcal meningitis and, in some specific circumstances, H. influenzae type b meningitis. In these instances, there are preventative actions that are recommended to protect close contacts.

The most common causes of bacterial meningitis:

• Meningococcal Disease (Neisseria meningitidis)
  Meningococcal disease is an illness caused by a bacteria called Neisseria meningitidis. It often causes meningitis but it can also cause bloodstream infections, pneumonia, joint infections, and other illness.
  Basics | Statistics | College Students | Travelers | For Health Professionals
• Haemophilus Influenzae (Invasive Disease)
  Haemophilus influenzae type b (Hib) was once the most common cause of bacterial infection in children. Hib causes a variety of diseases including meningitis, bacteremia, and pneumonia.
  About H. influenzae | Statistics | H. influenzae, type b (Hib)
• Pneumococcal Disease (Streptococcus pneumoniae)
  The Streptococcus pneumoniae bacteria kills more people in the United States each year than all other vaccine-preventable diseases combined. Treating pneumococcal infections with penicillin and other antibiotics used to be effective, but the disease is becoming more and more resistant to antibiotic treatment, making immunization increasingly important. There are more than 90 known strains of pneumococcal disease, and two different vaccines, often called "pneumonia shots," that help combat pneumococcal disease.
  Pneumococcal Disease Basics| Pneumococcal Information For Health Professionals | Pneumococcal Disease Statistics

More about bacterial meningitis

• CDC: Bacterial Meningitis
  CDC: Frequently asked questions about bacterial meningitis (Meningococcal disease, Neisseria meningitidis).

Viral Meningitis

The most common causes of viral meningitis is a group of viruses known as enteroviruses, which includes coxsackieviruses and echoviruses.

• CDC: Viral (Aseptic) Meningitis 
  Provides frequently asked questions about viral meningitis, several viruses cause Meningitis.
   
• Reporting Meningitis (caused by viral agents)
  Health professionals and others who provide care must report meningitis (caused by viral agents) to MDH within one working day.