This is a link post for "Salt, Sugar, Water, Zinc: How Scientists Learned to Treat the 20th Century’s Biggest Killer of Children" in the second issue of Asterisk Magazine, now out. The question it poses is: oral rehydration therapy, which has saved millions of lives a year since it was developed, is very simple. It uses widely available ingredients. Why did it take until the late 1960s to come up with it?
There's sort of a two part answer. The first part is that without a solid theoretical understanding of the problem you're trying to solve, it's (at least in this case) ludicrously difficult to solve it empirically: people kept trying variants on this, and they didn't work, because an important parameter was off and they had no idea which direction to correct in.
The second is that the incredible simplicity of the modern formula for oral rehydration therapy is the product of a lot of concerted design effort not just to find something that worked against cholera but to find something dead simple which did only require household ingredients and was hard to get wrong. The fact the final solution is so simple isn't because oral rehydration is a simple problem, but because researchers kept on going until they had a sufficiently simple solution.
I've finally properly read the linked piece, and it is in fact excellent. I'm curating this post; thanks for link-posting the article.
Among other things, I really appreciated the descriptions of moments when cures were almost discovered. A number of such moments happened with ORS/ORT, but a brief outline of this happening with vitamin C and scurvy (which is used as an illustration of a broader point in the piece) is easier to share here to give a sense for the article:
I also really appreciated the description of how this treatment went from carefully monitored hospital settings to treatment centers and field hospitals in a crisis, and even to household cures (a feat that involved comics, advocacy by a famous actress, and door-to-door education).
Here's another excellent passage from near the end of the article, which is related to Kelsey's second point: