Meningitis is an infection of the three membranes (called meninges) covering the brain and the spinal column. Meningitis can be caused by both bacteria (such as Haemophilus influenzae type B) and viruses (such as herpes simplex). Symptoms of meningitis include fever, intense headache, nausea and often vomiting. Newborns and elderly people are vulnerable to infection because their immune systems may be weaker. People with head injuries are also susceptible to infection. For more information, see the health unit's Meningitis Fact Sheet.

Encephalitis is the inflammation of the brain. It can be caused by bacteria such as those that cause meningitis or viruses (e.g. West Nile virus). Encephalitis is often a complication of other diseases such as syphilis.

Certain cases of encephalitis and meningitis are grouped together for surveillance because they can be difficult to clinically differentiate at the early stages of disease onset. The graphs below include meningitis and encephalitis cases caused by bacteria or viruses that are not reportable as any other disease. For example, if West Nile virus is detected as the infectious agent reponsible for encephalitis, then this is reported as a case of West Nile virus and not encephalitis. Meningitis caused by the bacteria Neisseria meningitidis is reported as invasive meningococcal disease and is not included in these graphs.

The following graph shows the number of encephalitis and meningitis cases in Simcoe Muskoka between 2000 and 2008. There are many factors that influence how many cases are reported to the health unit, as explained on the Infectious Diseases page.

The following graph shows the incidence rate of encephalitis and meningitis in Simcoe Muskoka and Ontario between 2000 and 2008.

There is alot of variability in the Simcoe Muskoka incidence rate, which means that there are many peaks and valleys and it is difficult to determine whether an increase is significant or whether it is within the expected range for this disease. The Ontario incidence rate has remained relatively stable between 2000 and 2007.