Civilization picked up speed after the discovery of agriculture and animal husbandry, allowing for longer lifespans, healthier people, and lots of population growth. Unfortunately, with population growth comes denser living quarters, enabling contagious diseases to spread more quickly. As humankind spread across the globe in waves of migrations, so did epidemics of unfathomable destruction.

We take for granted the knowledge that infection is caused by microscopic organisms. But the road to this scientific truth has been long and winding, and medical professionals have taken some pretty odd detours along the way. Hindsight being 20/20, we can examine this path and see the seeds - or germs - of germ theory as we know it today.

What happens after laboratory tests confirm that an environmental product kills bacteria? Is that the end of the line for testing a product's efficacy? One pair of researchers say no. Here is their proposal for an evidence hierarchy that describes how, in theory, data can begin to connect a product to a reduction in HAIs. While many regulatory agencies exist to protect the consumer by ensuring that HAI reduction claims are true, it is important for us to still be aware of the burden of proof in research, and how that plays out in a laboratory and real-life setting.