meningococcal

Meningococcal refers to disease caused by Neisseria meningitidis, a Gram-negative diplococcus that colonizes the human nasopharynx. In most carriers the bacteria do not cause illness, but occasionally they invade the bloodstream and meninges, causing meningitis or meningococcemia, and less commonly pneumonia or septic arthritis. Several serogroups (A, C, W, Y, X) are associated with disease worldwide; vaccines targeting serogroups A, C, W, and Y (MenACWY) are widely used, while group B (MenB) vaccines are also available in many countries.

Transmission occurs through close contact and respiratory droplets. Carriage is common in healthy people and can be increased in settings with crowding or poor ventilation. Outbreaks are monitored by public health authorities, and close contacts of a case may require prophylaxis.

Clinical presentation ranges from mild symptoms to life-threatening disease. Meningitis presents with fever, headache, neck stiffness, and photophobia; meningococcemia may cause fever with a purpuric or petechial rash, hypotension, and multiorgan failure. Rapid progression necessitates early recognition and treatment.

Diagnosis relies on lumbar puncture with CSF analysis and culture, though blood PCR and cultures can support a diagnosis when meningitis is suspected. Treatment requires prompt empiric IV antibiotics, usually a third-generation cephalosporin such as ceftriaxone, with adjustment when susceptibility is known. Supportive care in an intensive care setting is often required.

Prevention focuses on vaccination and management of contacts. Routine vaccination for adolescents or travelers is common, and post-exposure prophylaxis with rifampin, ciprofloxacin, or ceftriaxone is recommended for close contacts of a case. Early diagnosis, rapid treatment, and vaccination have reduced meningococcal disease incidence in many regions.