Background: Warts are very common in primary schoolchildren. However, knowledge on wart epidemiology and causes of wart transmission is scarce.
Objectives: To determine the prevalence of warts in primary schoolchildren and to examine the relation with environmental factors in order to provide direction for well-founded recommendations on wart prevention.
Methods: In this cross-sectional study, the hands and feet of 1465 children aged 4-12 years from four Dutch primary schools were examined for the presence of warts. In addition, the children's parents completed a questionnaire about possible environmental risk factors for warts.
Results: Thirty-three per cent of primary schoolchildren had warts (participation rate 96%). Nine per cent had hand warts, 20% had plantar warts and 4% had both hand and plantar warts. Parental questionnaires (response rate 76%) showed that environmental factors connected to barefoot activities, public showers or swimming pool visits were not related to the presence of warts. An increased risk of the presence of warts was found in children with a family member with warts [odds ratio (OR) 1.9, 95% confidence interval (CI) 1.3-2.6] and in children where there was a high prevalence of warts in the school class (OR per 10% increase in wart prevalence in school class 1.6, 95% CI 1.5-1.8).
Conclusions: One-third of primary schoolchildren have warts. This study does not find support for generally accepted wart prevention recommendations, such as wearing protective footwear in communal showers and swimming pool changing areas. Rather, recommendations should focus on ways to limit the transmission of wart viruses within families and school classes.