Largely yes, but I would point out that humanities resistance to disease is vastly better than individual resistance to disease.

For example Rabies has close to 100% fatality rate when untreated and has been a threat for vastly longer, but COVID more people over the last 100 years. So what’s a serious threat to an individual doesn’t necessarily mean a major threat to a larger population.

In that context there was likely significant protection offered by our aversion to the ill when we were primitive tribes with limited contact to each other. Such aversion could act as an external immune system causing most excessively deadly to burn out and pushing for ever less deadly strains over time.

Fair points. But do we actually have a biological aversion to illness? That strikes me as cultural (and fairly recent). I understand things like leper colonies to be exceptional, not typical. We've had various theories of disease before scientific ones and they mostly didn't consider contagion.

There’s competing reactions, taking care of sick family/tribe members has obvious benefits and prior exposure is likely. Anyway, it’s hard to say how much of this is cultural, but multiple cross cultural aversions at least have the side effect of reducing contact with disease.

“Pathogen avoidance: Uncanny stimuli may activate a cognitive mechanism that originally evolved to motivate the avoidance of potential sources of pathogens by eliciting a disgust response. "The more human an organism looks, the stronger the aversion to its defects, because (1) defects indicate disease, (2) more human-looking organisms are more closely related to human beings genetically, and (3) the probability of contracting disease-causing bacteria, viruses, and other parasites increases with genetic similarity."[8] The visual anomalies of androids, robots, and other animated human characters cause reactions of alarm and revulsion, similar to corpses and visibly diseased individuals.[9][10]” https://en.wikipedia.org/wiki/Uncanny_valley

People’s near universal aversion to the smell of rotting flesh and human shit are similar examples. Of course at the individual level this is less universal. Another possibility is heightened pain response around minor skin damage compared to larger injuries. Aka thorns and paper cuts hurt so much because that kind of injury was actually more dangerous than moderate blunt force trauma which damages more flesh but doesn’t risk infection.

PS: That said it’s not like we can actually test these theories. It’s mostly an interesting idea that seems plausible.