E. Coli and sickness

[apland at mala.bc.ca]

Hi. I'm a grade 12 biology student.  I am wondering about the effects of E. 
Coli bacteria injested through uncooked meat. Recently a young child died and 
tens of others have became ill in Washington State after eating uncooked 
hamburgers.  The news attributed the illness to E. Coli, but my biology text 
says that E.Coli is a harmless bacteria found in the colon.  Does this have 
something to do with the high pH in the colon as apposed to the low pH in the 
stomach? 

Thanks, Shannon