Say that an individual with a decent, but not mastery level, understanding of health, medicine, and sanitation were to travel to an era with technological level roughly around medieval to Renaissance levels.

Lets say this individual is able to get people to listen to him sufficiently to enact policy based off of his suggestions. I'm wondering how much disease can be minimized or removed simply from understanding of sanitation and how diseases spread. I do not want to look at more difficult medical intention like developing vaccines/antibiotics or knowing specifics of any one dangerous disease, only the more generalized knowledge. So I'm looking at things like:

  1. Boiling water to kill bacteria before using it for medical procedures (or even drinking it for those with weakened immune systems).
  2. Using boiled water to clean hands and instruments before medical procedures
  3. keeping urine and feces from being dumped straight into the river people drink from
  4. Knowledge of how diseases spread leading to suggestions like use of face mask, teaching people to cover sneezes up, avoiding physical contact with ill, and sanitizing or destroying things which came into contact with ill's bodily fluids
  5. Modern quarantine methodologies.
  6. Scientific approach to identifying which method an illness spreads by and attempts to focus treatment and quarantine to those methods it spreads. Including disposing of animals that may spread disease like black plague.
  7. safe disposal of diseased bodies.
  8. Removing of blatantly wrong medical presumptions that may be harmful.

Assuming these ideas are spread by this individual I'm trying to determine how much disease and illness may be prevented. I'm looking at general illness/death to common diseases primarily, but also somewhat interested in usefulness for treating a specific epidemic that may currently be ongoing.

My problem is I don't have a sense of scale as to what approaches were already known by a given period in time, and which were still foreign. Thus I'm trying to determine how effective these were and how much these would likely already be done.

In theory I don't want to limit this to time-travel, but any situation where modern knowledge meets a group of roughly the technological level I mentioned, even if it were some planet with a new sapience, some parallel universe with alternate history, or a magical portal to a different realm. I realize without the scope of an exact time period it's harder to say, but my point is I'm curious as to what would be expected to be known given this rough technological level, NOT what a specific country may have known.

  • $\begingroup$ Europeans routinely dumped their "night waste" in the streets every day. This is why some European streets have a deep trough in the middle. Wagon wheels would not get caught in the trough and rains would eventually wash away the feces, helped by the trough. $\endgroup$
    – Bulrush
    Commented Jun 8, 2016 at 11:46

3 Answers 3


What you’ve provided to your people is insight into how to avoid being infected. Assuming that the majority of the population in a kingdom adopts your rules vigorously (see my last point) you could seriously impact the spread of many diseases.

Germ theory and a true understanding of how disease works didn’t come about until the late nineteenth century. Boiling water to make it safe to drink wasn’t a known precaution until around that same time. This is a time period in which the so-called Medical Renaissance brought about such tremendous insights as simple human anatomy and theories about blood circulation. Even new and clever techniques like tying off arteries were eventually abandoned because without antiseptics the procedure was incredibly dangerous. What’s more, this knowledge was unpopular and restricted to the musings of a select few physicians.

For a Renaissance peasant (and even royalty) to suddenly believe Germ theory might result in absolute horror at their surroundings and lifestyle. The filth, dirt, and bodily fluids everywhere would become immensely disturbing. If impacted enough, a desire for cleanliness might jumpstart some interesting public works for sanitation.

Outside of the possibility of a general trend toward greater cleanliness, behavior and policies would change based on sewage and simple interaction with water and food. Boiling water and simply being aware of how disease spreads would be a major boon for everyone regardless of class. It might scare existing or potential doctors from doing their jobs, and they would need reassurance and training in proper health techniques.

You’d also need to consider the possibility that the general public might have few ways to affect public policy such as sewage handling and river preservation — in some kingdoms the rulers would have no interest in spending the money on those things and simply improve their own behavior. Some of the above techniques can still be employed by the peasantry, but they could still be at significant risk.

One critical final note: though you’ve hand waived away the problem of getting everyone to believe you and adopt these ideas, it is the most difficult part. The reason the effects would be so staggeringly effective on the population is because of how thoroughly difficult this task has been (and continues to be today). Even in 2014, when an Ebola outbreak struck Africa, it took a global effort to convince the locals how to adopt a proper response.

  • $\begingroup$ I was sort of thinking I would post a follow up question on how to convince people, after seeing how this answer goes. Big thing is that I didn't want to discover I was over-estimating the affect of the benefit. $\endgroup$
    – dsollen
    Commented Jan 20, 2016 at 0:34

All of your suggestions would have been excellent towards helping prevent disease, but your assumption that you would get them to believe about modern germ theory, based on bacteria, which cannot be seen with the naked eye, is simply outrageous for their brain-washed minds. Religion was at the core of everything during the Dark Ages, there was a reason they called it the Dark Ages. If the Bible couldn't explain it then most people believed it was witchcraft. And if you didn't toe the party line and attribute everything to God, you could be fined or imprisoned for witchcraft or sorcery. At one point there were even fines if you didn't go to church every Sunday.

Read two free EPUBs about the Black Plague here.


Almost all of it, modern medicine is far more about preventing illness (asepsis) than about curing it afterwards. An ounce of prevention....

Assuming you could get people to do things right you'd stop cholera and dysentery dead, prevent a lot of wound infection but not all of it, and you'd even make a dent in individual epidemics of plague, smallpox and the like.


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