Neisseria meningitidis is a type of bacteria that can cause serious infections, particularly meningitis, which is an inflammation of the protective membranes covering the brain and spinal cord. This bacterium is often found in the throat and nasal passages of healthy individuals but can become harmful under certain conditions. Transmission typically occurs through respiratory droplets, making close contact with an infected person a risk factor. Symptoms of meningococcal disease can include fever, headache, and a stiff neck, and it requires prompt medical attention to prevent severe complications or death. Vaccines are available to help protect against some strains of this bacterium.