The here and now - Ann Brashares

Seventeen-year-old Prenna James emigrated to New York when she was twelve. But Prenna didn't come from a different country, she came from a different time - a future where a mosquito-borne illness has mutated into a pandemic, killing millions and leaving the world in ruins.

Prenna and the others who escaped to the present day must follow a strict set of rules: never reveal where they're from, never interfere with history, and never, ever be intimate with anyone outside their community. Prenna does as she's told, believing she can help prevent the plague that will one day ravage the earth and take the lives of her younger brothers. But everything changes when she falls for Ethan.

She might be able to save the world ... if she lets go of the one thing she's found to hold on to.