Fact Sheet Meningococcal diseases
Meningococcal disease is caused by a bacterium known as Neisseria meningitidis (also called as meningococci). Twelve serogroups of N. meningitidis have been identified. Of these, group A is the commonest agent responsible for outbreaks in Asia. How is the disease transmitted The bacteria are transmitted from person to person through droplets of respiratory or throat secretions. Close and prolonged contact (e.g. kissing, sneezing and coughing on someone, living in close quarters or dormitories (military recruits, students), sharing eating or drinking utensils, etc.) facilitate the spread of the disease. The average incubation period is 4 days, ranging between 2 and 10 days. N. meningitidis only infects humans; there is no animal reservoir. The bacteria can be carried in the pharynx and sometimes, for reasons not fully known, overwhelm the body’s defences allowing infection to spread through the bloodstream and to the brain. It is estimated that between 10 to 25% of the population carry N.meningitidis at any given time, but of course the carriage rate may be much higher in outbreak situations. CLINICAL Features of the disease All infected individuals do not develop meningitis. Among those who develop meningitis, the most common symptoms are stiff neck, high fever, and sensitivity to light, confusion, headaches and vomiting. Even when the disease is diagnosed early and adequate therapy instituted, 5% to 10% of patients die, typically within 24-48 hours of onset of symptoms. Bacterial meningitis may result in brain damage, hearing loss, or learning disability in 10 to 20% of survivors. A less common but more severe (often fatal) form of meningococcal disease is meningococcal septicemia which is characterized by a haemorrhagic rash and rapid circulatory collapse. OUTBREAK CONTROL STRATEGY 1. 2. 3. 4. 1. Early diagnosis and prompt treatment Vaccination Chemoprophylaxis Risk communication Early diagnosis and prompt treatment
The diagnosis of meningococcal disease is suspected on the clinical presentation. However, diagnosis is confirmed through culture of cerebrospinal examination obtained on lumbar puncture. The identification of the serogroups as well as testing of susceptibility to antibiotics can be carried out in specialized laboratories. Meningococcal disease has a high case-fatality rate and is therefore potentially fatal. Cases with meningitis should be invariably hospitalized. Early recognition and prompt treatment can prevent serious illness or death. Admission to a hospital or health centre is necessary. As the disease is spread through droplets (and in crowded and congested situations), adequate spacing and good ventilation need to be considered, although strict isolation of the patient may not be necessary. Antimicrobial therapy must be commenced as soon as possible after the lumbar puncture has been carried out (if started before, it may be difficult to grow the bacteria from the spinal fluid and thus confirm the diagnosis). A range of antibiotics may be used for treatment including penicillin, ampicillin, chloramphenicol, and ceftriaxone. 2. Vaccination
Several vaccines are available to prevent the disease. Polysaccharide vaccines, which have been available for over 30 years, exist against serogroups A, C, Y, and W135 in various combinations. All these vaccines have been proven to be safe and effective with infrequent and mild side effects. The vaccines may not provide adequate protection for 10 to 14 days following injection. Routine vaccination: Routine preventive mass vaccination has been attempted and its effect has been extensively debated. Saudi Arabia, for example, offers routine immunization of its entire population. Sudan and other countries (to prevent frequent outbreaks) routinely vaccinate school children. Preventive vaccination can also be used to protect individuals at risk (e.g. travellers, military, pilgrims).
Protection of close contacts: When a sporadic case occurs, the close contacts need to be protected by a vaccine and chemoprophylaxis with antibiotics to cover the delay between vaccination and protection (as the vaccines may not provide adequate protection for 10-14 days following injection). Vaccination for outbreak control: Since even large scale coverage with current vaccines does not provide sufficient “herd immunity”, the current WHO recommendation for outbreak control is to mass vaccinate every district that is in an outbreak phase, as well as those contiguous districts that are in alert phase. It is estimated that a mass immunization campaign, promptly implemented, can avoid 70 % of cases. However, decisions on geographic extent of mass vaccination coverage need to be evaluated on a case-by-case basis taking into account all epidemiological and laboratory information, assessed risk for spread, and resources available. 3. Chemoprophylaxis
Chemoprophylaxis for close contacts with appropriate antibiotics is effective in not only preventing but also reducing carrier state. Antibiotics used for chemoprophylaxis are ciprofloxacin, rifampicin, minocycline, spiramycin, and ceftriaxone. 4. Risk Communication
Communities can play critical role in containment of outbreak and protection of individuals. The risk factors and possible control strategies should be communicated to them by the health authorities and communities in turn should Implement prevention and control measures as advised by Public Health Officials. Risk factors like overcrowding can be avoided by the communities and immediate medical care can be sought by early recognition of the signs and symptoms of the disease in any family member. The surveillance and notification of cases in the community can also be facilitated by the cooperation of the communities. * Adapted from WHO