dystopian ya novel about a rage virus?

Hi, I read this years ago so many of the details are shaky. I’m looking for a young adult dystopian novel about a girl that wakes up in her home to find her family gone and a mysterious dot on her wrist (there’s something special about her; immunity maybe). I think her brother had gone rabid and attacked her in the opening scene. She leaves to find her family and meets a man along the way and over the course of the book they fall in love (I think). There are some scenes where she meets people living in sewers or underground. There’s also a scene toward the end where she comes face to face with the people who have taken her family. Please help me!!