Bacteria are carried by various 'media', which can include raw food, moist surfaces where bacteria have been left, our hands or skin and from coughing or sneezing (打喷嚏).
2018年12月四级真题（第三套）阅读 Section B
Unless you're sitting next to someone who is coughing or sneezing, you shouldn't worry too much about getting sick.
2019年12月四级真题（第三套）阅读 Section A
柯林斯高阶英汉双解学习词典释义
VERB
打喷嚏
When you sneeze, you suddenly take in your breath and then blow it down your nose noisily without being able to stop yourself, for example because you have a cold.