Eurosurveillance

ECDC

Invasive Meningococcal Disease in Denmark in 2010

 Rediger
  Published: 16.08.12 Updated: 16.08.2012 10:54:01

J.N. Rasmussen1, L. Lambertsen2, A. Mygh3, S. Hoffmann2, P. Valentiner-Branth1

1Dept. of Epidemiology, Statens Serum Institut, Copenhagen, Denmark
2Dept. of Microbiological Surveillance & Research, Statens Serum Institut, Copenhagen, Denmark
3Medical Office of Health, Copenhagen, Denmark

Citation: Rasmussen J.N., Lambertsen L., Mygh A., Hoffmann S., Valentiner-Branth P. Inva-sive Meningococcal Disease in Denmark in 2010. EpiNorth 2012;13:8-12

Abstract
In Denmark, invasive meningococcal disease (IMD) is monitored via the clinical notification system and the Neisseria and Streptococcal Reference Laboratory which receives meningococcal isolates from the departments of clinical microbiology in Denmark. Here we describe the notified cases of IMD in Denmark in 2010 and the devel-opment of IMD by serogroup in the period 1980 to 2010. In 2010, 73 patients with IMD were notified, 39 had meningitis, 22 septicaemia and 12 both meningitis and septicaemia. Of the 73 cases, 36 (49%) were diagnosed with serogroup B, 26 (36%) with serogroup C and one (1%) with serogroup X, one (1%) with Y, and one (1%) with E29. In eight cases (11%) the serogroup was unknown. No cases of serogroups A or W135 were notified. Seven patients (10%) died from IMD. Since 1987 there has been a decrease in the number of IMD cases, which has mainly been driven by a decrease in serogroup B. Serogroup C has shown an increasing tendency over the past years. Through out the period 1980 to 2010 there has been a low number of serogroup A, Y, X and W135 cases. The increase in serogroup C has continued into 2011. In 2009 and 2010, an increased occurrence of the C:2a:P1.2.5 type with fine-type C:5.2:F3.3 was observed, a type associated with an increased risk of death. Devel-opments are therefore followed closely.

Introduction
In this report we describe the notified cases of invasive meningococcal disease (IMD) in Denmark in 2010 and the development of IMD by serogroup in the period 1980 to 2010.

Material
In Denmark, IMD is monitored via the clinical notification system and the Neisseria and Streptococcal Reference Laboratory which receives meningococcal isolates from the departments of clinical microbiology in Denmark.(1) Physicians receiving patients for treatment in Denmark are by law obliged to immediately notify the case when clinical suspicion arises; by phone to the Medical Office of Health in the region where the patient resides and in writing to the Department of Epidemiology, Statens Serum Institut. This National Notification System for IMD has held information on all mandatory notifications of IMD from clinicians since 1 January 1980. It has previously been shown that the notification system captured >90% of cases annually in the period 1994–2002(2,3).

Methods
From the clinical notifications and the results from the Neisseria and Streptococcal Reference Laboratory, infor-mation were collected on age, gender, clinical presentation (meningitis, septicaemia or both), the part of the coun-try where the case was from and where the case was suspected to be infected, sequelae from the disease and whether the patient died, how the meningococcus were detected (culture or polymerase chain reaction (PCR)) and the serotype of meningococcus.

Results
In 2010, the Department of Epidemiology received 73 notifications concerning patients with IMD, corresponding to an incidence of 1.3 per 100,000 population. A reminder had to be sent out to ensure notification in 30 (41%) of the cases. Table 1 presents the distribution by serogroup and table 2 the distribution by part of country.

 

Diagnosis
Among the 73 patients, 39 had meningitis, 22 septicaemia and 12 both meningitis and septicaemia. Of the 73 cases, 36 (49%) were diagnosed with IMD serogroup B, 26 (36%) with serogroup C and one (1%) with serogroup X, one (1%) with Y, and one (1%) with E29. In eight cases (11%), the serogroup was unknown. No cases of serogroups A or W135 were notified. In 59 (81%) of the notified cases, meningococci were detected by culture; four of these cases were also detected by PCR. In one case, both PCR and microscopy were positive; in another PCR and meningococcal antibody testing (MAT) were positive, and in another MAT and microscopy were positive. Four cases were only diagnosed by PCR, one case only by microscopy, and four cases only by MAT. In two cases, the diagnosis was based exclusively on clinical observations. A total of 69 cases were presumably infected in Den-mark, one case abroad, and in three cases the country of infection was unknown.

Case clusters
Two small outbreaks of group B were observed in North Zealand in 2010: two children attending the same kindergarden were diagnosed with IMD and the whole institution was offered ciprofloxacin prophylaxis. Two months later in the year, a pair of siblings were diagnosed with IMD, both attending the same after-school centre, but two different classes at the same school. A symptom-free third child from the same family as the siblings with IMD attended the kindergarden where the first outbreak had occurred earlier in the year. In the latter cases, families and all pupils from the children's school classes and after-school centre were offered ciprofloxacin prophylaxis. The meningococci from both outbreaks belonged to the same clone (sero- and serosubtype: P3.15; P1.7,16 and porA; fetA sequencetype 7,16; F3-3); one of the most frequently occurring clones in Denmark. Whether the two out-breaks were directly connected, is therefore difficult to establish.

Sequelae
In 2010 seven patients (10%) died from IMD. Five of these had IMD of serogroup B and two of serogroup C. All had septicaemia and five also had meningitis. The case fatality rate in the period 1995-2010 varied between 3 and 10% (figure 1). Among the 66 survivors in 2010, information on sequelae was available in 55 cases, including 49 (89%) cases with no sequelae. Following IMD, six persons experienced impaired hearing, bilateral deafness, bal-ance and coordination difficulty, possible reactive arthritis, neuritis, headache, and fatigue, respectively.



Meningoccal disease in the period 1980 to 2010
Since 1987, when the number of IMD cases was at its highest level (n=287) in the period 1980 to 2010, there has been a decrease in the number of cases (figure 2). This decrease has mainly been driven by a decrease in serogroup B, from 164 cases in 1987 to 36 cases in 2010. Serogroup C has shown an increasing tendency over the past years, in 2004 there was 14 cases compared to 26 in 2010. Through out the period there has been a low number of sero-group A, Y, X and W135 cases.



Discussion
In 2010 Denmark observed 73 cases of meningoccal disease corresponding to an incidence of 1.3 per 100,000 population, which is higher than the overall notification rate in Europe of 0.92 per 100,000 population in 2009 (4). There has been an overall decrease in number of cases over the last 25 years, which is mainly driven by a decline in serogroup B cases, whereas a slight increase in serogroup C cases has been observed.

This increase in serogroup C has continued into 2011, and by 1 September 2011, a total of 36 serogroup C cases had been diagnosed, making serogroup C more frequent than serogroup B. All meningococcal isolates undergo determination of serotype and sub-serotype and fine-typing. In 2009 and 2010, an increased occurrence of the C:2a:P1.2.5 type with fine-type C:5.2:F3.3 was observed. This type has been found to be associated with an in-creased risk of death (5,6), and has caused an increased occurrence of serogroup C disease in several European countries (7). Developments are therefore followed closely.

References
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2. Howitz MF, Samuelsson S, Mølbak K. Declining incidence of meningococcal disease in Denmark, confirmed by a capture-recapture analysis for 1994 and 2002. Epidemiol. Infect. 2008 Aug;136(8):1088–95.
3. Howitz M, Krause TG, Simonsen JB, Hoffmann S, Frisch M, Nielsen NM, et al. Lack of association between group B meningococcal disease and autoimmune disease. Clin. Infect. Dis. 2007 Nov 15;45(10):1327–34.
4. European Centre for Disease Prevention and Control. Surveillance of invasive bacterial diseases in Europe 2008/2009. 2011 Stockholm: ECDC;
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6. Howitz M, Lambertsen L, Simonsen JB, Christensen JJ, Mølbak K. Morbidity, mortality and spatial distribu-tion of meningococcal disease, 1974-2007. Epidemiol. Infect. 2009 Nov;137(11):1631–40.
7. Trotter CL, Ramsay ME. Vaccination against meningococcal disease in Europe: review and recommendations for the use of conjugate vaccines. FEMS Microbiol. Rev. 2007 Jan;31(1):101–7.


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