Witch Wood: The Harvesting Series Book 4

Harm none, and be ready for zombies. 
In the little town of Brighton, Amelia's practice of Wicca marks her as a curiosity both at home and at school. But Amelia can't change what she is. Knowing how to see auras, heal, and cast spells comes naturally to her. Only Madame Knightly, the ancient matriarch and owner of Witch Wood Estate, to whom Amelia plays caretaker, doesn't seem to mind. In fact, the crumbling old mansion is full of oddities.

However, when modern treatments fail to make a dent in the flu outbreak sweeping the globe, those who once ridiculed her white witchcraft turn to Amelia for help. While her eucalyptus tinctures prove no more effective than western medicine, her spell-casting is another matter. The residents of Brighton soon depend on the very magic they once ridiculed to save their lives.