On Doctoring MEDLINE searches, with reference librarian comments

The question was

"What is the incidence of water-borne
gastrointestinal diseases in rural areas (esp. New England)?"

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1 :  Parasites/         {1227}
2 :  Water/         {33427}
3 :  1 and 2         {6}
4 :  exp bacterial infections/ or exp disease outbreaks/ or exp         {365887}
gastroenteritis/ or exp water microbiology/ or exp water
supply/
5 :  1 and 4         {66}
6 :  limit 5 to english language         {37}
7 :  from 6 keep 14,21-22         {3}
8 :  from 6 keep 5,14         {2}
9 :  exp giardia/ or exp giardia lamblia/         {1620}
10 :  exp New england/         {14924}
11 :  exp United states/         {390682}
12 :  (9 and 10) or (9 and 11)         {85}
13 :  from 12 keep         {27}
1,3,5,8,11,13-14,16,20,22-23,27,36,39,44,46-48,52,54,57,60,63
,65,68-69,73
14 :  from 13 keep 1-27         {27}
15 :  exp camping/ or exp recreation/ or exp rural health/ or exp         {56408}
travel/
16 :  (1 and 15) or (9 and 15)         {53}
17 :  from 16 keep 2-3,8-9,20,30,51         {7}
18 :  from 17 keep 1-7          {7}

Reference Librarian comments

Clearly, you were having a good time with MEDLINE, learning and
strategizing as you went along. Congratulations. Good job.