Acute Encephalitis

All cases fulfilling stated criteria for encephalitis and aseptic meningitis in Olmsted County, Minnesota, for the period 1950 through 1981 were identified. This is, to our knowledge, the first such incidence and trend study in a delineated population, providing rates per 100,000 person-years of 7.4 for encephalitis (189 cases) and 10.9 for aseptic meningitis (283 cases). These are about twelve and six times higher, respectively, than the rates reported by the Centers for Disease Control. The rates have been stable over successive 5- or 10-year periods except for a recent increase in aseptic meningitis. Both conditions were more common in the summer months, in childhood, and among males. Viral identification using conventional laboratory tests has improved with time; in the period 1970 through 1981, virus type was specified in about one-fourth of the cases. The most common agents identified were California and mumps viruses in encephalitis, and entero and mumps viruses in aseptic meningitis. Antecedent and/or concurrent infections were noted in 42 and 35% of encephalitis and aseptic meningitis cases, respectively. No case due to mumps, measles, or rubella viruses has occurred since 1972, reflecting the impact of immunizations. Recovery was reported at the end of the acute phase in 95% of patients with aseptic meningitis, and there were no deaths. Seventy-eight percent of encephalitis patients recovered completely; the case fatality rate was 3.8%. Of the encephalitis cases, 2% were diagnosed initially postmortem.

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Epidemiology of encephalitis in children: A 20‐Year survey

Koskiniemi

Rautonen

Lehtokoski-Lehtiniemi

et al. 1991

Annals of Neurology

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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)

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Acute Encephalitis

Cited by 38 publications

References 21 publications

Treatment of Reversible or Arrestable Dementias

Treatment of Reversible or Arrestable Dementias

Encephalitis and aseptic meningitis, Olmsted County, Minnesota, 1950–1981: I. Epidemiology

Epidemiology of encephalitis in children: A 20‐Year survey

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