a) Compare the relative contributions of a treated water supply and the collection, treatment and disposal of human wastes towards the control of epidemic diseases in developing countries. If there are insufficient resources for both systems, should one be given priority over the other? Explain.
b) During an epidemic of contagious diseases, why doesn't everybody get infected?
c) Why are viruses difficult to remove from a water supply system?
d) List at least five of the main factors affecting the health of the community.
e) What are the differences between airborne infectious diseases and diseases that are caused by air pollution? Give at least two examples for each category of diseases.