[Annual epidemics of hepatitis A in four large cities related to holiday travel among immigrant children].
OBJECTIVE: Analysis of the transmission pattern of hepatitis A in relation to ethnicity and travel behaviour in Amsterdam. Utrecht, Rotterdam and The Hague. DESIGN: Descriptive study of notified cases. SETTING: Municipal Health Services of the four major cities in the Netherlands. METHOD: Notification data of hepatitis A in Amsterdam, Utrecht, Rotterdam and The Hague were analysed over the period 1992-1995. Cases were analysed according to age (0-19 years or > 19 years), whether or not they travelled abroad in the period of six weeks before the onset of the first symptoms of disease, and endemicity of hepatitis A in the country of ethnic origin. RESULTS: The strong increase of hepatitis A after the summer holidays could be divided into several smaller epidemics starting with an epidemic among children of Moroccan and Turkish descent who had spent the summer holidays in these countries, among children of the same ethnic background who had not travelled abroad, followed by epidemics among non-travelling children and adults of mainly Dutch descent, respectively. A strong correlation was found in Amsterdam between the incidence in the former two groups and the latter two groups (Pearsons r = 0.68; p = 0.004). CONCLUSION: Children who spent the summer holidays in a hepatitis A endemic country, particularly Morocco and Turkey, appeared to be the main importers of hepatitis A in the four major cities. Active immunization of all children born in the Netherlands of Moroccan and Turkish descent is the most preferable intervention.