What is the difference between a population approach and a high-risk
approach in epidemiology/public health?

Dear Big Mamma, 

The High Risk Approach involves "Identification of persons at highest
risk; and Intensive treatment of these high risk individuals to reduce
their risk" (Source: Thomas A. Pearson, Introduction to Public Health,
University of Rochester - Power Point Presentation
<http://www.cvhpinstitute.org/daniel/present/pearson2001b/pearson2001b.ppt>).

The "Population", or "Public Health" approach, on the other hand,
assumes that the general public should be protected against diseases,
not only those in risk groups. The whole population should be
educated, so that the risk will be lowered.

The difference, as you could see, is in the focal population (general
public vs. those considered high risk) and in the strategies. For
example, Pearson writes that "The Problem with the high risk approach:
 Most cases of heart disease and stroke come from average risk or
moderately increased risk persons."

More information
================
Association of Schools of Public Health
<http://www.asph.org/document.cfm?page=724> on the population approach

Shah Ebrahima and Edith Laub, "Commentary: Sick populations and sick
individuals", International Journal of Epidemiology 2001;30:433-434,
<http://ije.oupjournals.org/cgi/content/full/30/3/433>.

I hope this answered your question. My answer was based on an online
search for ["population approach" "public health" "high risk"] :
://www.google.com/search?num=50&hl=en&lr=&ie=UTF-8&oe=UTF-8&q=%22population+approach%22+%22public+health%22+%22high+risk%22

Please contact me if you need any further clarifications on this
answer before you tip/rate it.