The authors sincerely apologize for the oversight in omitting the acknowledgements in the original manuscript. The acknowledgements are printed below.

The authors thank Professor John Threlfall and the staff of the E. coli, Shigella, Yersinia and Vibrio (ESYV) Reference unit of the Laboratory of Enteric Pathogens (LEP), Health Protection Agency in London, England for typing the human strains to the molecular level. Their rapid response and efforts provided further evidence to link all cases to the swimming pool.