When I was a teen, I visited Mexico with my brother and family on vacation and almost everyone in our group contracted a stomach bug from local water supply. We drank bottled water, but local food was prepared with local water supply. Since then, I'm always very careful to bring my own water supply when traveling - even for cooking whenever possible. Considering how technologically advanced China is, I would assume their food and water supply are very safe. Please confirm this is true. Also, if possible, I need to know what are the common illnesses you might contract when traveling in China, so I can know what to be vaccinated against.