Answer:
Worldwide health issues are complex real-world problems because this problems are usually caused by diseases, pests, vectors and poor hygiene. All the factors listed vary according to geographical and economic conditions. Hygiene is good and better in first world countries such as USA and very poor in Third World countries.
Pests and diseases are also sometimes peculiar to a certain area which makes the issue of solving world health issues a very complex one as a result of it not being universal most of the time.
