Escherichia coli is a common cause of infections in all populations and countries of the world, causing an enormous burden of disease. In this issue of Clinical Microbiology and Infection, Al-Hasan et al. describe seasonal peaks in the incidence of E. coli bloodstream infection (BSI) during the summer for a population of 125 000 in Minnesota, USA. We discuss the probability that similar seasonal peaks in the incidence of E. coli BSI occur in other populations and geographical regions. Second, we discuss possible underlying explanations for these findings in terms of seasonal changes in human behaviour and the effect of temperature on the ability of E. coli to survive in the environment. Finally, we discuss some of the possible implications of E. coli BSI being a seasonal illness. More specifically, we discuss how better understanding the reasons for seasonality may potentially help us to better understand the dominant routes by which human populations are exposed to clonal groups of E. coli associated with urinary tract infection.