But in the past, vigilance towards alien species was focused only on the risk of their carrying infectious diseases or insect pests which would infect livestock, attack crops or directly affect human health.
但過去對境外物種的警戒心，都放在它們是否帶來傳染病、蟲害，進而感染、侵犯家禽畜、農作物，與是否對人類直接造成傷害。