Infection with E. coli<unk> :H7 can come from ingestion of contaminated food or water, or oral contact with contaminated surfaces. Examples of this can be undercooked ground beef but also leafy vegetables and raw milk. Fields often get contaminated with the bacterium through irrigation processes or contaminated water naturally entering the soil. It is highly virulent, with a low infectious dose: an inoculation of fewer than 10 to 100 CFU of E. coli<unk> :H7 is sufficient to cause infection, compared to over one-million CFU for other pathogenic E. coli strains.
Escherichia coli O157:H7
Escherichia coli O104:H4
Escherichia coli O121
Escherichia coli O104:H21
Campylobacter upsaliensis
Enteroaggregative Escherichia coli
Salmonella
Vibrio cholerae