Neisseria meningitidis exists in the nasopharynx of about 5-10% of the population and rarely causes serious disease. Severe meningococcal disease can occur when the bacterium enters normally sterile areas of the body, penetrating through the mucous membranes of the nose and throat. While N. meningitidis can cause infection in the blood or lungs, it is also a major cause of meningitis in both children and adults. Meningococcal meningitis develops when bacteria infects and causes inflammation of the meninges or the tissue surrounding the brain and spinal cord. High fever, headache, and stiff neck are typical symptoms of meningococcal meningitis. These symptoms can develop over several hours or may take 1 to 2 days. Other symptoms may include rash, nausea, vomiting, photophobia, confusion, and sleepiness. As the disease progresses, patients may also experience seizures. Without antibiotic treatment, patients with invasive meningococcal disease can die.