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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
