Meningococcal infection is an acute infectious disease caused by meningococci. The infection is characterized by a variety of clinical manifestations ranging from an asymptomatic bacteria carrier state to sepsis and meningitis. The severity of the disease and the probability of developing fulminant forms with high case fatality emphasize the importance of this pathology. Prevention requires interaction between epidemiologists, bacteriologists, paediatricians and specialists in infectious diseases.
Meningococcal infection occurs everywhere and is considered to be a public health issue in different countries despite some advances in control and intervention (1, 2). Annually, there are 500,000 cases of generalized forms of meningococcal infection (i.e. meningitis and meningococcal sepsis) and 50,000 lethal outcomes registered in the world (3). The global incidence of meningococcal infection is primarily determined by epidemics in the countries of the "meningitis belt" including Burkina Faso, Niger, Ethiopia, Benin, and Sudan (4). In Europe the maximum incidence rate (6-13 cases per 100,000 population) was registered in Iceland, Ireland, and Scotland. In England, Belgium, and the Netherlands the incidence rates were 3-6 cases per 100,000 population. In the Russian Federation the epidemiological situation related to meningococcal infection has been comparatively favourable during the last 5 years. However, there are some zones in Russia where the incidence of meningococcal infection is still high, for example the north of the European Russia where Arkhangelsk oblast is situated (4). Arkhangelsk oblast belongs to the Northwestern Federal District with a population of 1,280,000 and an area of 58,900 square kilometres (5).
The goal of this study was to determine the epidemiological characteristics of meningococcal infection in Arkhangelsk oblast.
Materials and methods
This study was based on a comparative analysis of meningococcal infection incidence registered during 1989-2007 in Arkhangelsk oblast and the Russian Federation. The data were analyzed using descriptive methods. The incidence data were provided by the Directorate of the Federal Service for Surveillance on Consumer Rights Protection and Human Well-Being (Rospotrebnadzor) in Arkhangelsk oblast. This service registers all confirmed cases of meningococcal infection. Bacteria carriers are not subject to registration and therefore not included in the analysis.
During the study period from 1989 through 2007, meningococcal infection incidence in Arkhangelsk oblast remained high and was higher than the average incidence in country. The maximum incidence in the region, 6.6 per 100,000 population, was reported in 1991 and exceeded the average incidence of meningococcal infection in the Russian Federation by 65%. The annual increase in the infection-related morbidity in Arkhangelsk oblast ranged from 24% in 1993 to 41% in 2002. Since 2005 a tendency toward a decline in meningococcal infection has been reported. In 2005 and 2006 the incidence was 3.8 and 3.1 per 100,000 population, respectively. In 2007 the lowest incidence during the period, 1.9 cases per 100,000 population, was reported. This incidence was the same as the average incidence registered in Russia (Fig.1).
Fig. 1. Incidence of meningococcal infection in Arkhangelsk oblast and the Russian Federation (per 100,000 population), 1989-2007
While 50-90% of all cases of meningitis are reported among children under the age of 5 (6), meningococcal infection is dangerous for people of all age groups, from infants to senior citizens. The majority of patients in Arkhangelsk oblast with invasive forms of meningococcal infection were also children. The share of patients under the age of 14 varied from 73.8% in 1999 to 53.6% in 2006 and 62.5% in 2007. Among 478 patients registered during the study period 284 (59.4%) were children (Fig. 2).
Fig. 2. Proportion of cases of meningococcal infection by age in Arkhangelsk oblast, 1998-2007 (n = 478)
The only year when the majority of patients were found to be adults (patients over 15 years of age) was 2003. For the same year children under the age of 14 accounted for 28.2% of all cases. However, over the whole study period the infection was more frequently registered among one to two year-old children (Fig. 3).
Fig. 3. Proportion of cases of meningococcal infection among children by age in Arkhangelsk oblast, 1998-2007 (n=284)
During this decade, the incidence of meningococcal infection among children under the age of 14 in Arkhangelsk oblast was higher than in the Russian Federation (Fig. 4).
Fig. 4. Incidence of meningococcal infection among children <14 years of age in Arkhangelsk oblast and the Russian Federation, 1997-2007 (per 100,000 population)
The infection incidence was highest in 1997 and 2002 with 16.2 and 19.2 cases per 100,000 children under the age of 14, respectively. The lowest incidence was registered in 2003 with 6.0 cases per 100,000 children as compared to the average incidence of 11.7 reported in the Russian Federation. In 2007 the incidence of meningococcal infection registered in Arkhangelsk oblast and the Russian Federation was approximately equal with 8.0 and 8.2 cases per 100,000 children under the age of 14, respectively.
The seasonal variation of infection in Arkhangelsk oblast is similar to other regions of the country with most cases registered in winter and spring. The analysis of long-term data shows that in Arkhangelsk oblast a sporadic increase in the incidence was usually reported in October and the highest number of patients was registered in November and in May. The incidence was lowest in July and August. Detection of serological groups of meningococci is very important for epidemiological surveillance of meningococcal infection. Meningococci serological groups А and С are considered to be epidemic types while serogroup B is most often detected during periods of sporadic morbidity (4). The longterm monitoring data indicated that in Arkhangelsk oblast meningococci of group B prevailed in the microbial landscape (22.1%) followed by group С (17.3%) and group А (2%). However, it is important to note that a considerable proportion of the meningococci (51.7%) were not serotyped. The most important task for Arkhangelsk oblast at present is to study the biological properties of meningococci strains obtained from patients. International studies might be particularly effective in terms of defi ning genetic properties of meningococci and their genetic barcode.
The share of meningococci representing other serogroups was low in Arkhangelsk oblast: Х (3.3%), Y (1.1%), 29 Е (1.1%), Z (0.8%), and W-135 (0.8%). Generalized clinical forms of meningococcal infection prevailed, ranging from 67.3% in 2003 to 87.5% in 2007. Among children under the age of 14 generalized forms were particularly frequent, from 77.4% in 1999 to 100% in 2003 and 2006. In 2007, the proportion of generalized forms declined to 86.6% (Table 1).
Table 1. Proportion of generalized forms of meningococcal infection among children under the age of 14 in Arkhangelsk oblast, 1998-2007 (n = 252)
Years / годы
Children under age of 14 / дети до 14 лет
Meningococcal infection / менингококковая инфекция
Generalized form / генерализованная форма
Proportion of generalized forms / удельный вес генерализованных форм
Total no. / абс.
Total no. / абс.
Total / итого
Annually, some fatal outcomes of meningococcal infection are registered in Arkhangelsk oblast. These cases are usually caused by brain oedema, brain swelling or infectious toxic shock in association with hypertoxic forms of the infection. In 2001-2008 the case fatality rate of generalized forms of meningococcal infection in Arkhangelsk oblast was 65.4% among children and 34.6% among adults.
Prophylaxis for meningococcal infection is vaccination (7). Meningococcal vaccination is included in the immunization schedule developed in response to epidemic indications. The following vaccines are registered in the Russian Federation: a vaccine for meningococcal infection serogroups A, А and С (Gabrichevsky State Unitary Enterprise of Bacterial Preparations, Russia) and the Meningo A+C vaccine (Sanofi Pasteur, France).
Vaccination response to epidemic indications is performed when the incidence of the prevailing meningococcal serogroup is at least twice as high as in the previous year. Vaccination is initiated following a resolution from the chief state sanitary doctor of the Russian Federation or chief sanitary doctors in regions of the Russian Federation. Children from 1 to 8 years of age and first-year students at institutes of higher education (especially students from different parts of Russia or from any other country) are subject to immunization with the polysaccharide vaccine. During an epidemic, emergency immunization is performed in the foci of the generalized form of meningococcal infection without the identifi cation of serogroup. During inter-epidemic periods immunization is provided within the foci of verified meningococcal serogroups using the appropriate serogroup containing vaccine (7).
In Arkhangelsk oblast and the Russian Federation an inter-epidemic period for meningococcal infection of more than 5 years has been registered. The incidence continues to decrease.
The prevailing group of patients is children. The highest incidence rate is registered among infants one to two years of age.
The majority of meningococci in the microbial landscape are non-typeable. Meningococci of serogroup B prevail among all other serological groups.
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