Invasive meningococcal disease is a severe infection caused by Neisseriameningitidis. Although the disease is rare, it is one of the most feared infectious diseases because it afflicts healthy individuals with a rapidly progressing disease, a high case-fatality rate and a substantial risk of sequelae. In the years to come, N.meningitidis is likely to be responsible for a larger proportion of bacterial meningitis cases due to the impact of the Haemophilus influenzae type B vaccine and, more recently, the conjugated pneumococcal vaccine that will probably be introduced in more countries. It is therefore important to address measures to reduce the burden of invasive meningococcal disease.
The disease manifests itself as meningitis and/or septicaemia and the incidence is highest among young children and teenagers. In Europe, the overall incidence has decreased in recent years to approximately 1 per 100,000 population. For the countries participating in the EpiNorth project, the incidence in 2008 ranged from 0.5 to 3.8 per 100,000 with the highest incidence reported from Murmansk oblast.
In Europe, most cases of invasive meningococcal disease are caused by N. meningitidis serogroups B and C. A number of European countries have seen high incidences of group C infection and most of these countries have included conjugated meningococcal group C vaccines in their childhood immunisation schedule. United Kingdom was one of the first countries to introduce vaccination (in 2000). Belgium, Germany, Greece, Iceland, Ireland, The Netherlands, Portugal, Spain, and Switzerland also include group C vaccines in their national programmes. Vaccination has resulted in a substantial reduction of meningococcal disease caused by group C infection without any apparent serotype replacement. While this is promising, the long-term effect of conjugate vaccines is currently being debated. Continued public health surveillance data is therefore important to address the effectiveness of intervention strategies.
Although there has been great interest to develop universal group B N. meningitidis vaccines, at present no universal vaccine available. One challenge for vaccine development is the inadequate immune response to group B capsular polysaccharide antigens used in vaccines. While there have been attempts to control outbreaks of specific group B N. meningitidis phenotypes by targeted vaccines based on outer membrane proteins such as the PorA protein, these vaccines will only have a limited effect on the control of group B infections in general. Hence, it is important to continue research to develop universal group B vaccines.
In the absence of effective control by immunisation, the management of invasive meningococcal disease continues to be an important task for public health practitioners. Management includes the identification of cases and contacts, the application of chemoprophylaxis and vaccination (most commonly in cases caused by N. meningitidis group C) as well as providing information to the community and media. The approach by which these measures are applied differs between European countries. The variation in public health practice reflects historical traditions and the fact that the quality of the evidence for some of the interventions is poor. However, evidence indicates that household contacts of cases of invasive meningococcal disease should be offered prophylactic antibiotics in order to eradicate carriage of N. meningitidis. The European Centre for Disease Prevention and Control, ECDC, has established an expert group to assess the different practices. It is hoped that this evidence-based guidance for public health management will assist countries in reviewing their own policies of managing meningococcal disease.
This issue of the EpiNorth journal presents two articles addressing meningococcal disease. The papers highlight challenges for outbreak control and surveillance. L.Glushkova and R.Galimov describe an outbreak of N. meningitidis group C in the city of Pechora in the Republic of Komi. The outbreak included five teenagers among whom two died. As a response to this outbreak, chemoprophylaxis was prescribed to 557 individuals and 757 contacts of patients were immunized. In another paper, L.Titova and co-authors describe the epidemiology of meningococcal disease in the Arkhangelsk oblast. As in many other settings, the incidence of meningococcal infection has decreased in recent years. However, the explanation for this consistent observation is not fully understood. Serogroup B was the most common serogroup followed closely by group C. Unfortunately, as many as 52% of the isolates were not serotyped. To obtain a better understanding of the dynamics of the different subtypes of N. meningitidis, it is essential to ensure that strains are characterised, in particular to detect the emergence of group C serotypes or “successful” clones of serogroup B.