Cryptosporidium in asymptomatic children.

Recent reviews state that cryptosporidiosis is a disease particularly of young children, but we have found the opposite age distribution, with no cases in children less than 5 years old. No Cryptosporidium species was detected in fecal samples obtained from 423 healthy preschool children, for a prevalence of less than 0.24%. When these results were combined with our previous data (from a study of diagnostic stool samples), the prevalence of Cryptosporidium among children less than 5 years of age in the Helsinki area was calculated to be less than 0.18%. The worldwide prevalence of Cryptosporidium among asymptomatic children is less than 0.5% if a few exceptional localities with high prevalences (which probably have a local explanation) are excluded from the calculations. Since the Helsinki area turned out to be no exception, the age distribution of symptomatic cryptosporidiosis also needs further study that would take into account simultaneous asymptomatic carrier rates and a significant local variation.