shiori_makiba has posted the poem "Metamorphosis" about another victim of the berettaflies, the second one to develop superpowers. A character sheet appears after the verses. So it looks like about 1:12 manifestations in victims stung. That's a lot. The overall pattern, however, is pretty consistent with zetetic exposure: most people get sick, a handful die, a very few develop superpowers. Anything life-threatening can do that, but the high rate of manifestation coupled with the fact that both new soups have related powers suggests that the venom contains a metagen which can bestow powers, not just activate latent ones.