VOA慢速英语:US Health Officials: Zika 'Scarier Than We Thought'

initially – adj. of or relating to the beginning

transmission – n. the act or process by which something is spread or passed from one person or thing to another

infect – v. to cause (someone or something) to become sick or affected by disease

vaccine – n. a substance that is usually injected into a person or animal to protect against a particular disease

continental US – n. the 48 states between Canada and Mexico; does not include Hawaii, Alaska or US territories such as Puerto Rico

Americas – n. the countries of North, Central and South America

dengue – n. a disease spread by mosquitoes that causes flu-like sympts.  It can develop into severe dengue, which can be fatal.

condom – n. a thin rubber covering that a man wears on his penis during sex in order to prevent a woman from becoming pregnant or to prevent the spread of diseases

screen – n. a sheet that is made of very small wire or plastic strings which are woven together and that is set in a frame in a window, door, etc., to let air in but keep insects out