Evil tourist - a play-by-post rpg

A normal family is visiting Barcelona (Spain). They come from Xiamen (China) and will be staying at the Mediterranean city for some days.
Ying Yue, the youngest daughter, has had a strange cough since they were waiting at the airport for boarding the long distance plane. She and her family have just landed and are on the way to the city center, in a regular bus. Li, her father, stares at her with some concern. He has seen that symptoms in the past.
That cough... was just the beginning.