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Epidemiology of encephalitis in children: a 20-year survey
M Koskiniemi1, J Rautonen, E Lehtokoski-Lehtiniemi
1Department of Virology, University of Helsinki, Finland.
Insights
Acute encephalitis in children is most common in toddlers. Post-vaccination, varicella-zoster virus and Mycoplasma pneumoniae are key causes, with varied etiologies in infants versus older children.
Area of Science:
- Pediatric Neurology
- Infectious Diseases
- Epidemiology
Background:
- Acute encephalitis affects children aged 1 month to 16 years.
- Incidence is highest in 1- to 1.9-year-olds (16.7 per 100,000 child-years), declining with age.
Purpose of the Study:
- To analyze the incidence, etiology, and demographics of acute encephalitis in children.
- To identify trends in causative agents before and after widespread vaccination.
Main Methods:
- Retrospective analysis of 405 pediatric encephalitis cases treated between 1968 and 1987.
- Data collected from the Children's Hospital, University of Helsinki.
Main Results:
- Post-1983, common agents include varicella-zoster virus, Mycoplasma pneumoniae, and respiratory/enteroviruses.
- Etiology varied by age: enteroviruses and herpes simplex virus in infants; respiratory viruses and Mycoplasma pneumoniae in older children.
- Male predominance noted, particularly in 4- to 9-year-olds (M:F ratio 1.4:1).
Conclusions:
- Vaccination significantly altered encephalitis etiology, reducing mumps, measles, and rubella-associated cases.
- Causative agents differ between infants and older children, with a notable proportion of unknown etiologies, especially in younger age groups.
- Sex-based differences in etiology were observed, suggesting potential biological or exposure variations.
Abstract:
Four hundred five children from the Helsinki area who were 1 month to 16 years old were treated for acute encephalitis at the Children's Hospital, University of Helsinki, from January 1968 through December 1987. Encephalitis occurred most commonly in children 1 to 1.9 years of age, among whom the incidence was 16.7 per 100,000 child-years. The incidence remained quite high until the age of 10 years, and then gradually declined to 1.0 per 100,000 child-years at the age of 15 years. Since 1983, when mumps, measles, and rubella vaccination eradicated the encephalitides associated with these microbes, the major associated agents have been varicella-zoster, Mycoplasma pneumoniae, and respiratory and enteroviruses. In infants younger than 1 year of age, the major agents were enteroviruses, herpes simplex virus, and the group of "others," whereas in older children, respiratory viruses and Mycoplasma pneumoniae, as well as varicella-zoster virus, dominated. In children aged 1 to 11 months, the causal agent could not be identified in one-half of all cases, whereas in children who were at least 10 years old, the etiology remained unknown in only one-fourth of cases. Male dominance was most evident in the 4- to 9-year age group. The difference in etiology between males and females was significant (p = 0.02); mumps and varicella were more common in boys, and adenovirus and Mycoplasma pneumoniae were more common in girls. The overall male-to-female ratio was 1.4:1. Characteristic seasonal variation occurred in encephalitides associated with mumps, measles, and entero- and respiratory viruses.(ABSTRACT TRUNCATED AT 250 WORDS)