Uroboros by Jason Reynolds

Rodrigo, an Amazonian expedition guide, is approached one night by a team of secretive scientists who want to trek into the rainforest and collect genetic samples from a remote tribe. They'll pay Rodrigo as much as he makes in a year, but they don't have a government permit, and they want to trek at night. And only at night. When economic hardships tempt this mild-mannered young man into taking a risk he'd otherwise avoid, Rodrigo's life takes a sudden and radical turn.

Lili's life is going nowhere. Between her mother's unreasonable expectations and society's soul-draining standards, she is dying to hit the existential reset button. When she drops out of school to pursue her own definition of happiness, she runs across Drew, another misfit who hates modern culture and has a subversive way of showing it. Lili thinks she's finally met someone she can relate to—only to learn that the outlaw persona is far from the most radical thing about her new friend.

Rodrigo and Lili have entered the world of the Uroboros. One of them will join this transhuman species. The other won't survive.

Uroboros once stood atop the evolutionary ladder, ruling the planet as gods until the rise of monotheism reduced them to demonic outcasts—to 'vampires'—a word they find offensive. Over the last few years, a mysterious disease has pushed these once supreme beings to the brink of extinction. Circumstances bring our protagonist to the Everglades where he/she meets a group of Uroboros desperately searching for a cure before it's too late. The protagonist joins them on a dangerous mission to help save the species, but, deep in the dark heart of Amazonia, a harrowing dilemma awaits—a dispute with apocalyptic implications.

What do you do when your means of survival turns out to be the source of your demise?