In a prospective nationwide laboratory-based surveillance study of all invasive bacterial and fungal infections among children < 16 years of age, 2,836 clinical cases were registered during the 5-year period 1985-1989. Of these cases, 136 were polymicrobial. During the study period, nationwide administration of Haemophilus influenzae type b conjugate vaccine reduced the incidence rates of invasive infection caused by this organism. The most common clinical diagnosis (48% of cases) was bacteremia without an identified focus of infection. The age-specific annual incidence rates of all invasive infections in children < or = 15 years of age, in children < or = 4 years of age, in children < or = 1 year of age, and in children < or = 28 days of age were 55.8, 141.4, 272.7, and 2,749.0 cases/100,000 person-years, respectively. Thirty percent of the children in the study had an underlying condition predisposing to infection. The case-fatality rate was 4.1% for all cases of invasive infection.

Acute appendicitis has previously been found to be associated with social class. In an attempt to confirm this, 125 patients with histologically verified acute appendicitis were compared with 1802 control children, randomly selected from the schools of the City of Helsinki. Social class determination was based on father's occupation in families with two parents, and on mother's occupation in single provider families. No association with social class was found. The proportion of single provider families was around 25% among both cases and controls. Appendicitis patients are one potential source of control groups in epidemiological studies.

No abstract