You get the same effect with veternarians and animals ... and any system that deals with living organisms.
We're incredibly complex. The variations are huge (my nerves are not in the right place as most people's, so the dentist has to inject more drugs
to numb an area for me. Some people have their hearts on the left side of the body, others on the right. Some people are born with a resistance to
certain drugs (I clear out painkillers pretty fast from my system) and others are overly sensitive to it. And we all describe and feel pain
differently (I walked around with a broken (smashed) wrist for 4 days before it occurred to me that something was wrong.)
The actual number of diseases and conditions a person can suffer from (singly or in combination with other conditions and diseases) is well over a
million. Over 250 organisms are known to cause foodborne illnesses. However, many different organisms cause similar symptoms, especially diarrhea,
abdominal cramps, and nausea. There is so much overlap that it is rarely possible to say which microbe is likely to be causing a given illness unless
laboratory tests are done to identify the microbe, or unless the illness is part of a recognized outbreak.
So... how good do YOU think you'd be at telling (for example) the differece in symptoms caused by these common foodborne illnesses:
www.fightbac.org...
Remember that docs can tell the difference between these and appendicitis and a lot of other things.
If you think it's that easy, start taking some courses in medicine. I think you'll change your mind.
(for the record, I did have some med school courses.)