School holidays and admissions with asthma.

The admission rate for asthma at a children's hospital was studied over an 11 year period. Admissions varied unpredictably over periods of a few days, but there was a repeated yearly pattern of peaks and troughs with an interval of several weeks. The short term variation could be attributed to chance effects alone, excluding any important role for short term influences--for example, weather changes--in precipitating asthma admissions. There was a definite association between the longer term variation and school holidays. The admission rate fell during holidays and there were two or more peaks during terms. The pattern is consistent with a largely viral aetiology for asthmatic attacks throughout the year. We postulate that school holidays disrupt the spread of viral infections in a community, with synchronisation of subsequent attacks. Travel during holidays may facilitate acquisition of new viral strains by the community.