Meningococcal disease 2023
2023 Annual Report on Meningococcal Disease
Invasive meningococcal disease (MD) covers meningitis, sepsis and culture or DNA detection of meningococci in material from normally sterile locations, e.g. joints. In Denmark, MD is clinically notifiable via the clinical notification system (SEI2) of the Danish Health Authority, and monitoring is handled by the Department of Infectious Disease Epidemiology and Prevention (DIDEP) and by the Neisseria and Streptococcal Reference Laboratory (NSRL) which receive meningococcal isolates and other biological material from the departments of clinical microbiology. The two monitoring systems continuously supplement each other.
MD is a list 1a condition cf. Executive Order on Notification of Infectious Diseases (retsinformation.dk) and is therefore notifiable by phone and in writing to the Danish Patient Safety Authority and Statens Serum Institut, see Sygdomsovervågning (ssi.dk, in Danish language) for more information about disease monitoring. The duty to notify serves, among others, to ensure rapid infection tracing to prevent secondary cases in close contacts through treatment with antibiotics and, when relevant, vaccination, see Guideline on prevention in case of meningococcal disease (retsinformation.dk), in Danish language. It is important to submit the sample to Statens Serum Institut for grouping and, if relevant, to offer relevant vaccinations to close contacts, see Invasive meningococcal disease, post-exposure prophylaxis (ssi.dk), in Danish language.
In 2023, the DIDEP received notifications on 32 patients with MD. Reminders had to be sent out in seven of these cases (22%), but no notifications were received.
Geography, sex and age
In 2023, the MD incidence was 0.5 per 105 inhabitants, which is an increase compared with previous years when the incidence was 0.3 (2022), 0.2 (2021) and 0.3 (2020). In 2017, 2018 and 2019, the incidence was 0.7, 0.6 and 1.0, respectively. The cases were evenly distributed across Denmark, but more cases were recorded in the City of Copenhagen and in East Zealand; the incidence varied from 0.2 to 1.2 cases per 105 inhabitants between areas, see Table 1. No cases were detected on the island of Bornholm.
MD occurred in most age groups, see Table 2. The median age was 30 years (range 0-87 years). The highest incidence was recorded in the < 1 year age group. More MD cases were observed in men than in women.
Diagnosis
Among the 32 patients, eight had meningitis, 16 had sepsis and seven had both meningitis and sepsis. Additionally, one patient was notified based on the clinical picture alone.
In 14 of the patients, MD was caused by group B (44%), whereas 13 patients had group Y (41%), one had group X (3%) and one had group 29E (3%). Three patients had no information on group (9%). No cases of serogroups A, C, W or Z were notified in 2023.
In 24 patients (75%), the presumed country of infection was Denmark. For one patient, the presumed country of infection was South Africa. For a total of seven patients, the presumed country of infection was not stated, as no written notification was received for these cases.
In 2022, group B was dominant, but an increase in the number of group Y cases was also observed. In 2023, the group Y increase continued. Therefore, group B and group Y now account for nearly the same number of cases. In 2023, group Y was detected mainly in patients aged more than 40 years. However, a total of four group Y cases were recorded in patients aged 14-29 years. Group B was detected in nearly all age groups in 2023. Group W, which increased steeply in 2019, has not caused any cases since 2021.
Following the introduction of restrictions to limit infection with SARS-CoV-2 in March 2020, the number of meningococcal cases has remained lower than was previously the case. The number of notified MD cases was twice as high in 2023 as in 2022. Even so, fewer cases than before the pandemic were observed (56 cases in 2019, 37 cases in 2018 and 39 cases in 2017), Figure 1.
Laboratory tests
Meningococci were detected by culture in 24 of the 32 cases, 23 of which were submitted to the SNR. All 23 isolates were susceptible to ceftriaxone, ciprofloxacin and rifampicin; 22, to penicillin. In eight cases, meningococci were not detected by culture; in seven of these cases, meningococcal DNA was detected using nucleic acid amplification technique (NAT), and in six of these cases, material was submitted to the SNR for NAT grouping.
Underlying diseases
Underlying diseases and late 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, whereas no time restrictions were applied for the remaining underlying diseases.
In 18 (56%) of the 32 patients with MD recorded in 2023, one or more underlying diseases were recorded, Table 3.
Among children below 14 years of age, no underlying diseases were recorded. A total of 18 of 28 persons aged 14 years or more had underlying conditions, among which pulmonary conditions and cancer were the more frequently occurring diseases.
Mortality and late sequelae
One adult patient with group Y died due to sequelae to MD in 2023, Table 2.
Late sequelae to MD were recorded in five patients in 2023. Hearing loss was the most frequently occurring sequela (three patients), Table 4. One patient had eye-sight-related late sequelae recorded, and one had hydrocephalus.
This annual report is also described in EPI-NEWS no. 12b/2024.