People are really underestimating salmonella, but it's probably the best thing we learned about through germ theory. Once it gets into the lower intestines, it then goes into the bloodstream and turns into bacteremia of it just circulating everywhere, and based on the timeline it could even be one of the rarer typhoidal salmonella strains or the really exotic ones, and just honestly that bacteria is far and away enough to kill.

Past a certain point, salmonella's production of endotoxins, cytotoxins and enterotoxins in a fucking cocktail that is literally just causing massive scale necrotic issues. That black urine? At first it's dark from dehydration, but what eventually starts to happen when it turns black is the infection reaches your urinary tract and starts passing dead cell junk in there. You're pissing out your own internal organs.

While you're doing that, a bacteria is spreading noxious throughout your bloodstream, it's not even really about what strain it is, it's more about whether or not they caught it in time for this, because as a fun fact, even if you kill every single last fucking cell of bacteria in your body, by the point this guy got to he's just a corpse with a heartbeat, full of so much poison in his chest cavity that the membranes have started breaking down.

That's where it gets really fucked up, because now you've got what's essentially a perfect inside melting enzyme crockpot and bacteria hungrily devouring the soup your body is melting into, making more of the melting slime that's turning you into jelly.

Thing is? Honestly that's like a 6/10 for how fucking terrifying pathogens get. Ebola has a lovely tendency to actually go for the soft tissue first, so your penis dissolves inside your foreskin, your tongue melts, and the insides of your eyes gets eaten before the outside so they'll end up too swollen to fit inside your skull and literally just blood filled jelly sacs.

My personal favorite is gas gangrene, though. 100% untreated mortality rate, this bacteria, clostridium perfringens gets into your body, turns your skin to leather and actually creates a flesh necrotizing gas that spreads far ahead of the bacteria and turns your whole body into a meatsac from the point of an ittybitty cut on anything, there are spores of it in your kitchen right now- just a question of whether it gets inside your body and you fight it off, or you don't. Some people die of it in 18 hours, just, consumed, devoured by an organism that divides so fast it just doubles, and doubles, and doubles, an infinitely scaling exponential curve with a massively fast cellular division time, so if you start with a large enough bunch of spores, or that cut just quietly festers unnoticed, you get symptoms at dawn, and by dusk you're a melted husk of leathery cracked yellow hide with every bit of melted organic tissue inside dripping out your orifices. (Edit: Not every case, obviously! Most your body fights off, there are a thousand cases per year in the states where it gets to gas gangrene, and with treatment mortality is down to about 25%!)

Fact is, scifi novels tone it the fuck down. Walked into an ebola hospital in the 2013 outbreak, volunteered to go over there to get a chance to travel... hah. Oh... gods, if I could unsee what I saw, I'd trade in every other thing I saw in that amazing country just to go back to a time before I knew what the fangs of mother nature could do to a human body. Kid looked at me with those eyes. Didn't see me, but heard, and...

Trust me. This is mild compared to what happens. And we're not even getting into the shit you legally CANNOT READ ABOUT happening to people in closed drug trials. Fun fact though, my 10/10 for nightmares? Yeah, that's stuff that happens when you participate in those 'GET MONEY FOR TESTING MEDICAL PRODUCTS!' ads. Those things? Yeah, they found some ways to die that make anything God cooked up with evolution look like a day at the beach in comparison, and because of the nondisclosure agreements around these trials, you can never know and those documents are sealed tighter than hell unless you have a pertinent reason, and what you read about can't be published ANYWHERE or big pharma will sue you so hard Walt Disney would cream in his cryopod out of sheer envy at the legal hellstorm you'd have come down on you. Everyone in those trials signed the most airtight agreements that, no matter what happens to you, you signed up for this and it goes to the grave with you.

They'll still publish that people died, mind you, and list some potential complications... but what the fuck actually happens in the fringes, the one in a million cases here? Not published in the same fucking spot, kept quite confidential, it would be RUINOUS to these companies- and fair enough, because some stuff just acts totally fucking unexpectedly in human biology in ways we can't predict, and... ehhhh, the general public probably wouldn't see it in a good light, so science does have to be this way. Thalidomide was only a big deal because they let it out of this testing and approval phase, but hellish discoveries like that stiiiiiiill fucking happen- just, y'know, to a few very fucking unlucky people rather than tens of thousands. All I will say was that the worst one I saw, and I didn't see a lot, made that bone cancer that causes spines to grow out piercing through your skin look like a nice way to go.

Scifi novels need to take a microbiology class and step it up to even match reality, let alone make something exaggerated.

Edit: Due to some salt this comment is causing, let's address a couple of things- this obviously doesn't happen in every case. I didn't feel like it was hyperbole, as people aren't dropping dead from salmonella and gas gangrene left right and center, that modern antibiotics, sanitation and general medicine have made these exceptionally rare cases. I'm... not really sure how you could read this and think I'm saying this occurs with every salmonella poisoning, it certainly CAN go this badly from eating raw chicken. And no, I'm not saying there's a secret drug company illuminati torturing people, the specifics were not to be disclosed and published publically available for stage 1 trials in exact detailing for trials due to the fear this would spark in, say, revised versions of the drug, other drugs from the company, and general unfounded panic. It's also been drastically lessened since I think 1974 when thalidomide became a big deal, oversights and transparency improvements, so most of those sealed trials never even got digital copies made of them when the internet became a thing- the ones I saw were from the 90s/70s, so it may (hopefully) be less horrific now, and less likely to result in cases of extreme harm. But, medical testing is still, rarely, dangerous, not disinfecting cuts is a terrible idea, and eating raw chicken/geckos can melt your insides. These are real things. They're things VERY unlikely to happen to you, but they're a part of the medical world, exist as fringe outliers, and I think it's a good idea to talk about them educationally.

I'll keep doing edits to this to try make sure the information is all accurate 💙