“Meningitis is an inflammation of the membranes that cover the brain and spinal cord. It can be caused by a number of infectious agents including viruses and bacteria. The type of meningitis and its cause can only be determined by conducting laboratory tests.
Viral meningitis (also called aseptic meningitis) is the most common type of meningitis and is less severe than bacterial meningitis. In Illinois, an average of 600 cases of aseptic meningitis is reported annually, with most occurring in late summer and early autumn. The majority of cases of aseptic meningitis are due to viruses called enteroviruses that can infect the stomach and small intestine. A small number of cases are caused by different viruses, which can be transmitted by infected mosquitoes; these are called arboviruses. Fatal cases of viral meningitis are rare and complete recovery is the rule.
Bacterial meningitis is often more severe than aseptic meningitis, particularly in infants and the elderly. Before antibiotics were widely used, 70 percent or more of bacterial meningitis cases were fatal; with antibiotic treatment, the fatality rate has dropped to 15 percent or less. Bacterial meningitis is most common in the winter and spring. Three bacteria cause the majority of cases: Haemophilus influenzae, Neisseria meningitidis or Streptococcus pneumoniae.”
Illinois Dept. Public Health-IDPH (https://dph.illinois.gov/topics-services/diseases-and-conditions/diseases-a-z-list/meningitis.html)