It may be useful to clarify these two concepts; the difference is in the water.
At a health resort the water is from thermal springs, that is a naturally occurring source of mineral water that emerges from the ground at more than 5 degrees warmer than the surface temperature, and that has health benefits because of the mineral composition of the water.
The water at a spa is usually heated rather than thermal, and the health benefits derive from the sensation of wellbeing that using the spa creates.Did you know that the word spa comes from the Latin salutem per aquam, which means health by water?