Why is everyone sick?

Hi all, I went to China, Guangdong last week and noticed like almost everyone coughing or snorting loudly (without a hand in front of the mouth and snorting like a pig does). Is this just etiquette over there? Or what's wrong?

Edit: I'm sorry for the people who I offended or will offend when you read this post, this wasn't my intention, I just wanted to see your people in better health