VOA慢速英语:科学家称废水中的病毒有助于追踪感染

toilet – n. a device used to expel body fluids and solids

track – v. to record the progress or development of something over time

outbreak – n. the sudden start of something unwelcome, like war or disease

sample – n. a small amount of something that represents what it is like

surveillance – n. the activity of watching people carefully, often secretly, especially by an army or police force

symptom – n. a change in the body or mind which indicates that a disease is present