What Causes Meningitis
Most cases of meningitis are the result of a viral infection, but some are caused by a bacterial infection. In rare cases, a fungal infection could cause meningitis. Since, bacterial meningitis infections are the most serious and can often be deadly, the source of the infection must be identified so that it can be treated effectively.
Every year, viral infections lead to more diagnosed cases of meningitis than bacterial infections. Fortunately, viral meningitis is often mild and clears up on its own. Most cases of viral meningitis in the U.S. have been linked to a group of viruses known as enteroviruses. These viruses tend to be more active during the late summer and early fall. However, viral meningitis can also be caused by HIV, West Nile virus, and mumps. Our clinical investigators are conducting an important meningitis vaccine clinical trial in DeLand, FL.
Acute bacterial meningitis is usually the result of a bacterial infection which has reached the patient’s brain and spinal cord. On the other hand, bacteria can invade the meninges directly via the sinuses, ears, and in very rare cases during surgery. There are a variety of bacterial strains capable of causing acute bacterial meningitis, but the most common include:
- Neisseria meningitidis (meningococcus): This is one of the leading causes of bacterial meningitis. Meningococcal meningitis is highly contagious, and it can easily cause local epidemics in military bases, college dorms, and boarding schools. Fortunately, there is a vaccine which helps to limit the number of infections which occur.
- Streptococcus pneumoniae (pneumococcus): This strain of bacteria is the most common cause of bacterial meningitis for infants, children, and young adults in the U.S. However, this bacterium is more likely to cause sinus infections or pneumonia than bacterial meningitis. There is also a vaccine which can protect against this infection.
- Haemophilus influenzae (haemophilus): This used to be the leading cause of bacterial meningitis in American children, until the implementation of the Hib vaccine. Nowadays, that vaccine has become a part of the routine childhood immunization schedule in the U.S., and the incidence of this type of meningitis has been greatly reduced.
- Listeria monocytogenes (listeria): This type of bacteria resides in some of America’s favorite foods (hot dogs, soft cheeses, and lunch meats). Odds are you have been exposed to this form of bacteria, but most people won’t become ill from listeria. However, people with weaker immune systems (pregnant women, newborns, and senior citizens) are more susceptible to this type of infection.
Fungal meningitis is fairly rare and it can cause chronic meningitis. Occasionally, it can be confused with acute bacterial meningitis, due to the mimicking of symptoms. Fortunately, this type of meningitis is not contagious. Some people who have aids or other immune deficiencies are more susceptible to developing a common fungal form of the disease known as cryptococcal meningitis. If antifungal medications are not used, then this disease can become deadly.
If a slow growing organism invades the membranes and fluid surrounding the brain, then this can lead to chronic forms of meningitis. While acute cases of meningitis can appear rapidly, chronic meningitis can take several weeks to develop. Still, chronic cases of meningitis share similar symptoms as acute meningitis.
Now, there are some noninfectious causes of meningitis, which were not examined in detail on this page. Meningitis clinical research has shown that things like cancer, inflammatory diseases, chemical reactions, and even certain drug allergies could all cause meningitis. If you are worried about the risk of meningitis for yourself or your children, then please talk to your doctor about the meningitis vaccine as soon as possible.