Global strategies to control infective disease have historically included the erection of barriers to international travel and — (24) —. Keeping people with such deadly disease outside national borders has — (25) — as an important public health policy in the human immunodeficiency virus (HIV) epidemic. Between 29 and 50 countries — (26) — to have introduced border restrictions on HIV-positive foreigners, usually those planning an — (27) — stay in the country, such as students, workers or seamen.

Question: Select the word that best fits blank (25).