I have used this unit for years with my fifth and sixth grade gutted/talented students.  They absolutely love it!!!!  The teacher must print off a fact sheet about ecoli, and I help the students put together a map of the buildings and physical features and sites involved.  We talk about water--ground seepage, watering of crops and animals, public water source contamination.  I share actual cases if water and meat contamination with them--including the big McDonalds nightmare.  They LOVE being the scientists!!

I have used Mystery Disease with my 7th graders for 4 years now and have had excellent results.  My students are challenged by the "problem" but not overwhelmed by it.  In order to arrive at a solution, students must evaluate, analyze, research, synthesize, consider different points of view and more.
In addition, everything I need to facilitate my students' learning is here!

I use the Mystery River problem with my 8th graders and think that it, too, is excellent!  My only complaint is that Mark Bohland has not written more of these accesible, yet challenging, problem-based learning units.