Ashes, Ashes by Jo Treggiari

Sixteen year old Lucy is surviving alone in the wilds of Central Park. The plagues, floods, droughts, and insane weather have wiped out 99% of the population.When Lucy meets another survivor, Aiden, she reluctantly joins his camp.  While life in camp is still difficult, Lucy enjoys being with people again, and eating fresh food. But things aren't quiet for long. The Sweepers are searching for something, and Lucy is on their radar.

I LOVED this book and I'm hoping for a sequel!