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An outbreak of serogroup B:15:P1.16 meningococcal disease, Frederiksborg County, Denmark, 1987-9
S Samuelsson1, P Ege, L Berthelsen
1Neisseria Department, Statens Seruminstitut, Copenhagen, Denmark.
Abstract:
Epidemiological features of an outbreak of group B:15:P1.16 meningococcal disease (MD) in Frederiksborg county, Denmark, 1987-9, were investigated. The study comprised 149 cases notified during the outbreak and the two preceding years; 115 were confirmed by the isolation of Neisseria meningitidis. In 1989 the incidence had increased to 14.1 per 100,000 population. Among group B strains, B:15:P1.16 accounted for 80% (77/97). The overall mortality rate was 10% (15/149). Regarding cases due to group B:15:P1.16 strains a significant time-space clustering, which exclusively occurred within the 10-19 years age group, was demonstrated. The link between cases within clusters was indirect or unknown, except for ten patients with contact to one particular school. The prophylactic measures used included administration of rifampicin to household contacts. During the outbreak the proportion of secondary cases was high (6-15%). All secondary cases occurred outside the household indicating that the household had been protected.
Insights
An outbreak of group B:15:P1.16 meningococcal disease in Denmark primarily affected adolescents. Secondary cases were mainly outside households, suggesting household protection.
Area of Science:
- Epidemiology
- Infectious Disease
- Public Health
Background:
- Meningococcal disease (MD) poses a significant public health challenge.
- Group B strains, particularly B:15:P1.16, have been implicated in outbreaks.
- Understanding epidemiological patterns is crucial for control.
Purpose of the Study:
- To investigate the epidemiological features of a group B:15:P1.16 meningococcal disease outbreak.
- To analyze incidence, mortality, and transmission patterns.
- To evaluate the effectiveness of prophylactic measures.
Main Methods:
- Retrospective analysis of 149 notified cases from 1987-1989 in Frederiksborg county, Denmark.
- Confirmation of Neisseria meningitidis isolates.
- Time-space clustering analysis, focusing on the B:15:P1.16 strain.
- Assessment of secondary case proportions and contact tracing.
Main Results:
- Incidence of MD rose to 14.1 per 100,000 in 1989.
- Group B:15:P1.16 strains accounted for 80% of group B isolates.
- Overall mortality rate was 10%.
- Significant time-space clustering of B:15:P1.16 cases occurred in the 10-19 year age group.
- High proportion of secondary cases (6-15%) occurred outside households.
Conclusions:
- The B:15:P1.16 strain was the predominant cause of the meningococcal disease outbreak.
- Adolescents (10-19 years) were particularly vulnerable to this strain.
- Household transmission was limited, suggesting effective household protection.
- Rifampicin prophylaxis in household contacts may have contributed to control.