Many scientists worry that parents are unintentionally breeding killer strands of bacteria that could result in untreatable Black plague-like epidemics.
Often when given anti-biotics, parents stop giving them to their children when the coughing, fever, etc. ends, often long before they're supposed to. Bacteria still living in the child grow immune to anti-biotics until germs that were initially mostly harmless become deadly.
I just realized that I only gave my son one of his anti-biotics this morning. This means I possess more biological weaponry than Saddam ever did. I'm heading for the fridge before the tanks show up.