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28 April 2015
Meningococcal Infection   

Causative agent

Meningococcal infection is caused by the bacteria Neisseria meningitidis.

Mode of transmission

The disease is mainly transmitted by direct contact through respiratory secretions from infected persons.

Incubation period

Varies from 2 – 10 days, commonly 3 – 4 days

Clinical features

The clinical picture may be variable. It may result in severe illness when the bacteria invade the bloodstream (meningococcaemia) or the membranes that envelop the brain and spinal cord (meningococcal meningitis). Meningococcaemia is characterised by sudden onset of fever, intense headache, purpura, shock and even death in severe cases. Meningococcal meningitis is characterised by high fever, severe headache, stiff neck followed by drowsiness, vomiting, fear of bright light, or a rash; it can cause brain damage or even death. The brain damage may lead to intellectual impairment, mental retardation, hearing loss and electrolyte imbalance. For invasive meningococcal infection, it can be complicated by inflammation of joints, inflammation of heart muscle, inflammation of the posterior chamber of the eye or chest infection.

Treatment

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.

Risk of infection

The risk of infection is higher among close contacts of patients with meningococcal infections. Close contacts include (1) family members, (2) day care centre contacts, (3) persons directly exposed to the patient's oral secretions, and (4) those who frequently sleep or eat in the same dwellings as the patient. Certain patients with defective immune systems are also at higher risk. Other risk factors include antecedent viral infection, overcrowding, chronic illness, and active and passive smoking.

In general, the risk of acquiring meningococcal infection while travelling is low. However, in sub-Saharan Africa extending from Senegal to Ethiopia, particularly during the dry season (December to June), disease occurrence is higher, and there is additional risk for long-term travellers living in close contact with the indigenous population.

Prevention

1.    Keep hands clean

  • Wash hands with liquid soap and water properly especially when they are dirtied by respiratory secretions e.g. after sneezing.
  • When hands are not visibly soiled, clean them with 70 - 80% alcohol-based handrub as an effective alternative.

2.    Cover nose and mouth while sneezing or coughing and dispose of nasal and mouth discharge in lidded rubbish bin.

3.    Travellers to high risk areas should consult their doctor before the trip to determine the need for meningococcal vaccination.

4.    Travellers returning from high risk areas should seek medical advice if they become ill. They should discuss their recent travel history with the doctor.

Meningococcal vaccination

At present, four preparations of meningococcal vaccines are registered in Hong Kong – one bivalent (serogroups A & C) and three quadrivalent (serogroups A, C, Y & W135) vaccines. The meningococcal vaccines do not confer protection against meningococcal infections caused by serogroup B and are lacking evidence of long-term protection. Locally, the incidence of meningococcal infections is low and about half of the meningococcal infections were caused by Neisseria meningitidis serogroup B.

To minimise the risk of meningococcal infection, vaccination may be considered for those staying in the sub-Saharan Africa during the dry season. Travellers visiting Saudi Arabia during the Hajj annual pilgrimage should bring along certificate of vaccination with the quadrivalent (serogroups A,C,Y & W135) vaccine against meningococcal infection issued not more than 3 years and not less than 10 days before arrival in Saudi Arabia.

Vaccination is generally not recommended for travellers making short-term business or holiday trips in areas of heightened meningococcal activity if they will have little contact with or exposure to local population in crowded conditions. There is insufficient justification to include meningococcal vaccine in the Childhood Immunisation Programme in Hong Kong in light of current evidence.

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