What is it?
In most countries, meningococcus is recognized as a leading cause of meningitis and fulminant septicaemia. It is classified into 12 serogroups based on the structure of the polysaccharide capsule. The majority of invasive meningococcal infections are caused by organisms expressing one of the serogroup A, B, C, X, W135 or Y capsular polysaccharides.
Neisseria species, which usually reside asymptomatically in the human nasopharynx, are easily transmitted to close contacts by respiratory droplets. Nasopharyngeal carriage of potentially pathogenic N. meningitidis has been reported in 4%–35% of healthy adults.1
Clinical features
Symptoms of invasive meningococcal disease (IMD) usually occur 1–4 days after infection. Signs and symptoms of IMD in infants and young children include fever, poor feeding, irritability, lethargy, nausea, vomiting, diarrhoea, photophobia and convulsions. The characteristic feature of meningococcal septicaemia is a hemorrhagic (petechial or purpuric) rash that does not blanch under pressure. Signs of meningitis in older children and adults include neck rigidity, photophobia and altered mental status, whereas in infants non-specific presentation with fever, poor feeding and lethargy is common. Besides meningitis and septicaemia, meningococci occasionally cause arthritis, myocarditis, pericarditis and endophthalmitis.
Most untreated cases of meningococcal meningitis and or septicaemia are fatal. Even with appropriate care up to 10% of patients die, typically within 24–48 hours of the onset of symptoms. Approximately 10% to 20% of survivors of meningococcal meningitis are left with permanent sequelae such as mental retardation, deafness, epilepsy, or other neurological disorders.
Mode of transmission
The disease is mainly transmitted by direct contact through respiratory secretions from infected persons.
Management
Meningococcal infection is a serious illness. Patients should be treated promptly with antibiotics. Close contacts would need to be placed under medical surveillance for early signs of disease and may be given preventive medications.
Prevention
Maintain good personal and environmental hygiene.
WHO recommendations: In countries where the disease occurs less frequently, meningococcal vaccination is recommended for defined risk groups, such as children and young adults residing in closed communities, e.g. boarding schools. Travellers or overseas students to high-endemic areas should be vaccinated against the prevalent serogroup(s). In addition, meningococcal vaccination should be offered to all individuals suffering from immunodeficiency, including asplenia, terminal complement deficiencies, or advanced HIV infection. Meningococcal vaccines against A, C, W, Y serogroup and vaccine against B serogroup are now registered in Hong Kong.