Meningococcal Disease 2020

2020 Annual Report on Meningococcal Disease

2020 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 and other biological material from the departments of clinical microbiology (DCM). MD covers meningitis, sepsis and culture or DNA detection of meningococci in material from normally sterile locations, e.g. joints.

In 2020, the Department of Infectious Disease Epidemiology and Prevention received 19 notifications concerning patients with invasive meningococcal disease.

In five cases (26%), a reminder had to be sent out for the notification in 2020.

Geography, sex and age

In 2020, MD incidence was 0.3 per 105 inhabitants, which constitutes an increase compared with previous years where the incidence was 1.0 (2019) and 0.6 (2018). The cases were distributed across Denmark; the incidence varied from 0.0 to 0.5 cases per 105 inhabitants.


MD occurred in all age groups, see Table 2. The median age was 21 years (range 0-80 years). The highest incidence was seen in children aged less than one year and in the 14-17-year age group. The distribution of cases between the sexes was equal with an M/F ratio of 0.9. No boys below 14 years of age were affected, and therefore the 14+ year group counted more men than women.



Among the 19 patients, four had meningitis, eight had sepsis and five had both meningitis and sepsis. Additionally, in two patients meningococci were found in synovial fluids only.

In two patients, MD was caused by group B (11%), whereas four patients had group C (21%), two had group Y (11%) and nine had group W (47%). For two patients, the diagnosis was made exclusively based on the clinical picture (11%).

All patients had become infected in Denmark.

In 2015-2018, the total annual number of MD cases remained stable around 40, but the number increased to 56 cases in 2019. In early 2020, the number of MD cases remained high, but as from the lock down caused by the SARS-CoV-2 epidemic in the spring, the monthly number of MD cases declined and remained low for the rest of 2020 period during which a total of 19 cases were recorded.

2019 witnessed a strong increase in group W cases, and the dominance of this group continued into 2020, when 47% of all cases were caused by group W. In 2020, group W was seen in most age groups. Figure 2 presents MD by serogroups for the years 2008-2020.

The 2019 annual report on MD describes the identification of a Danish subclone of group W which has been present since 2016 and which has been detected only in Denmark. In 2019, the Danish subclone accounted for 15 of the 23 group W cases. In group 2020, eight of the nine group W cases were genotyped, and seven of the eight cases belonged to the Danish subclone. In 2020, the subclone was recorded in East Jutland (n=2), North Jutland (n=3), West Jutland (n=1) and in the City of Copenhagen (n=1). All cases were sporadic and no outbreaks with the Danish subclone have been recorded.


In 11 (58%) of the cases, the diagnosis was made by blood culture; three of these cases were also diagnosed by PCR on spinal fluids. Iin four (21%) of the cases, the diagnosis was made by PCR on spinal fluids, and PCR-based grouping could be made in all of these cases. In one case, the group was determined based on throat swabs. A meningococcal finding in a throat swab is not an independent sign of invasive meningococcal disease, but in this case there were clinical signs of MD and also PCR-positive spinal fluids. Additionally, in two cases, the diagnosis was made based on culture of synovial fluid; and in two cases, it was based exclusively on the clinical picture.

Underlying diseases and predispositions

Underlying diseases/predispositions and sequelae were established by linking the civil registration numbers (CPR) recorded during the MD monitoring to data from the National Patient Registry.

These conditions were categorised into groups based on diagnosis codes. Infections were included as from one month prior to the current MD case, but no time restrictions were applied for the remaining underlying diseases/predispositions. In eight (42%) of the 19 MD cases recorded in 2020, one or more underlying diseases and/or predispositions were recorded, Table 3.


Five children below 14 years of age were diagnosed with MD in 2020. None of the five children had known underlying conditions. Among four children aged 14-17 years, one child had underlying conditions. In the 18-29-year age group, two out of three persons had underlying conditions. In the 40+ year age group, five out of seven persons had underlying conditions. Among these underlying conditions, endocrine conditions, coronary diseases and cystitis were the most frequently observed.

Mortality and sequelae

No patients died due to MD in 2020.

Sequelae were recorded in six patients following MD in 2020. Two were registered with headache, one needed rehabilitation, one had hearing impairment or hearing loss recorded, one patient had abnormal involuntary movements and one had another/unspecified finding in the nerve and muscoloskeletal system recorded.


This annual report is also described in EPI-NEWS no. 3-5, 2021.