VOA慢速英语:美国进行的更多试验找出冠状病毒是如何传播的

located - v. to be in a certain area or place

vulnerable –adj. easily hurt or harmed

guidelines –n. rules or instruction that shows or tells how something should be done

outbreak –n. a sudden start or increase of fighting or disease

re-congregate –v. to come together in a group or crowd another time or somewhere else

response –n. something that is done as a reaction to something else