>Don't you think low child mortality might be also to do with nutrition sewage systems etc

Absolutely, all that helps, but in some ways, it hurts, as well. Take polio, for instance. It really wasn't a big issue until the 20th century. The thinking is that with modern sewage systems and improved cleanliness, kids were no longer getting exposed early and developing immunity, so it became epidemic. I don't think we'd want to go back to the kind of filth that provided that immunity, so using medication to do so makes sense to me.

Tamar