This motivation [...] to be selfless [...] is THE cause of the problem.

I don't see how. I'll assume, at least for the sake of argument, that your account of how these things work out is accurate; how would it go any better if the volunteers had different, less selfless, motivation? And why blame the situation on the volunteers' selflessness rather than on any of the other elements in the situation -- the locals' preference for cheaper but worse medical care, the offers for the physicians to emigrate, the fact that the local physicians are dependent on money from the locals rather than being paid by the government as in some Western countries, the fact that the volunteers eventually go away?

Actually, I'm a bit confused by the description of the process. So, the problem is that the volunteers turn up, provide cheap medical care thus putting the local physician out of business, and then go away. If the volunteers stayed around, the locals would have cheap medical care all the time and presumably that's a good outcome. Now, why does the local physician emigrate to the West rather than just moving down the road to another village that doesn't have western volunteers? Is it because there's more money to be made by emigrating? (In that case, surely the temptation is there even without the western volunteers.) Is it because the village down the road also has volunteers undercutting the physician? (If that's commonly the case, then a large fraction of the country must be getting free medical care from these volunteers -- so are you sure they aren't doing more good than harm overall?) Is it because the village down the road has its own physician? (If that's commonly the case, then the country isn't so desperately short of physicians as you describe.) I dunno -- I'm just having trouble seeing how your account fits together. Is it actually well founded on evidence?

The only way to be a true altruist is to be anonymous.

Would those African rural outposts have been better off if their first-aid volunteers had all been wearing masks and keeping their identities secret?