Except for 2 provinces, Henan and Yunnan, AIDS is extremely rare in China. That said, it's growing rapidly. If I remember correctly, they had about 600,000 cases of HIV with a population of about 1.3+ billion. Compare this with the USA which has about 1.2 million cases with a population of 300 million. The odds of him getting AIDS though are pretty friggin low... Other diseases though, like chlamydia and gonnorhea are pretty common.