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[Meningococcal disease in Spain: seasonal nature and recent changes]
1Departamento de Estadística. Facultad de Biología. Universidad de Barcelona.
Background:
In this study we built a time series model in the time domain based on the cases of meningococcal disease declared every four weeks in Spain between 1972 and 1998 With the model we analyzed the incidence of the disease and examined whether an epidemic really took place at the beginning of 1997, or whether the values were in the range of expectations. At this time there was widespread social alarm in Spain, because there was considered to be an outbreak of meningitis. We also examined whether the incidence of the disease diminished during 1997 following the measures introduced by the Comisión Interterritorial del Sistema Nacional de Salud.
Method:
The data on the incidence of the meningococcal disease in Spain were obtained from the Boletín Epidemiológico Semanal, published by the Instituto de Salud Carlos III, declared from 1972 to 1998 and grouped every four weeks. The method corresponds to the time series model in the domain of time: the Box-Jenkins method.
Results:
In order to explain the behaviour of the disease during the years of the study we chose a model ARIMA(0,1,1) (0,1,1)13 that shows annual seasonal behaviour, with higher incidence in the winter and the beginning of spring, and lower incidence in summer. An intervention analysis showed that in March 1996 there was a level shift in the incidence of the illness. This lasted until September 1997, at which time the incidence returned to pre-1996.
Conclusions:
The measures of sanitary monitoring against the meningitis in the months of greater incidence, winter and beginning of spring must be intensified. Between spring 1996 and autumn 1997 the incidence of meningitis increased. Thereafter, until the end of 1998, there was a significant decrease in incidence, attributable to the performance of the health authorities.
Insights
Meningococcal disease incidence in Spain increased from spring 1996 to autumn 1997. Following public health interventions, incidence significantly decreased by the end of 1998.
Area of Science:
- Epidemiology
- Time Series Analysis
- Public Health Surveillance
Context:
- Meningococcal disease outbreaks cause significant public concern.
- Spain experienced social alarm regarding meningitis in early 1997.
- The study analyzes disease incidence data from 1972-1998.
Purpose:
- To model meningococcal disease incidence in Spain using time series analysis.
- To assess if the 1997 incidence represented an epidemic or expected values.
- To evaluate the impact of public health measures on disease incidence.
Summary:
- A Box-Jenkins ARIMA(0,1,1)(0,1,1)13 model identified annual seasonality with winter/spring peaks.
- Intervention analysis revealed a significant increase in incidence from March 1996 to September 1997.
- Incidence returned to pre-1996 levels by late 1997, persisting through 1998.
Impact:
- Public health monitoring during peak seasons (winter/spring) requires intensification.
- The study attributes the post-1997 incidence decrease to effective health authority actions.
- Findings inform future strategies for managing meningococcal disease outbreaks.