Methods
Study population
The study area is located in Kaengkhoi District, Saraburi
Province, Thailand, approximately 100 km northeast of Bangkok.
The area includes a small city with some industry that is
surrounded by rural villages that depend on agriculture for
income. Data from the 2001 census maintained by government
healthcare officers show a total population of 80 141 in
the catchment area, including 5686 (7%) children under 60
months of age.