2017 Annual Report on Meningococcal Disease

2017 Annual Report on Meningococcal Disease

In Denmark, invasive meningococcal disease (MD) is monitored via the clinical notification system (Form 1515) handled by the Department of Infectious Disease Epidemiology and Prevention and by the Neisseria and Streptococcal Reference Laboratory, which receive meningococcal isolates from the departments of clinical microbiology. MD covers meningitis, sepsis, and culture or DNA detection of meningococci in material from normally sterile locations, e.g. joints.

In 2017, the Department of infectious Disease Epidemiology and Prevention received 39 notifications concerning patients with invasive meningococcal disease.

In 11 cases, a reminder had to be sent out for the notification (30%). 

Geography, sex and age

In 2017, the MD incidence was 0.7 per 105 inhabitants. The cases were evenly distributed across Denmark; the incidence varied from 0 to 1.2 cases per 105 inhabitants between areas. 

Table 1 shows the distribution by area.


MD occurred in nearly all age groups. The median age was 27 years (range 0-96 years). Half of the patients belonged to the 0-29-year age group and the other half to the 40+ age group. The M/W ratio was 1.3, please see Table 2.



Among the 39 patients, six had meningitis, 28 had sepsis, and five had both meningitis and sepsis. 

In ten (26%) of the patients, MD was caused by group B, whereas one patient had group C (3%), eight had group Y (21%), 14 had group W (36%) and one had group 29E (3%), Table 2. No cases were notified of MD caused by group A, X or Z. For five patients, the group was unknown (13%). One of the notifications was based exclusively on the clinical picture; and for the four remaining cases, the SSI had not received an isolate or spinal fluid.

In 38 patients, the presumed country of infection was Denmark. One patient had been travelling until a few days before disease onset and had probably become infected in Switzerland. 

The total number of MD cases has remained stable for the past three years after having followed a decreasing trend since the 1990s. The relative occurrence of the different groups shifts over time.

Group B has been the most frequently occurring group, apart from in 2011 and 2012 when an increase was observed in the number of group C cases; but in 2017, the group W occurrence exceeded the group B occurrence for the first time ever. Figure 1 presents MD by groups, for the 2005-2017 period. 


Group C was previously more frequently occurring, but has been rare and declining since 2014. Group 29E is very rarely occurring and has been detected in blood culture as well as pharyngeal swabs in a young patient who is undergoing work up for complement deficiencies.


In 32 (82%) of the cases, meningococci were detected by culture, including four that were also detected by PCR. An additional four cases were diagnosed by PCR alone, one case by PCR and meningococcal antibody test (MAT), and one case by MAT alone. One patient was diagnosed based on the clinical picture only. The two last cases and three of the four cases diagnosed by PCR were not grouped. 

Underlying diseases 

Underlying diseases were established by linking the civil registration numbers (CPR) recorded in the MD monitoring with the National Patient Registry. Underlying diseases and sequelae were categorised into groups based on diagnosis codes. Infections were included from one month prior to the current MD case, but no time restrictions were applied for the remaining underlying diseases/predispositions. In 29 (74%) of the 39 cases of MD, one or more underlying diseases and/or predispositions were recorded. Two of the three children below one year of age had underlying disease prior to their MD. Ten of the 17 cases aged from 1 to 39 years had underlying diseases, see Table 3. In the group of patients above 40 years of age, 17 of 19 patients had underlying conditions. The four most frequent categories were cardio and pulmonary disease, endocrine disorder and cancer. 


Mortality and sequelae

In 2017, four patients (10%) died from MD, including one in the 14-17-year age group, two 18-29-year-olds and one 90+-year-old patient. Two of the fatalities had group B and the other two had group W MD.

Eight patients has MD sequelae recorded, including two with hearing impairment or hearing loss, one with thrombosis, three with headache and two who needed rehabilitation.