短语讲解：

1. The serum is known as zMapp. 

be known as 被认为是; 号称; 叫做
例句：So she will be known as Sleeping Beauty. 
所以她将会是众所皆知的睡美人。 

2. The two Americans became infected with the disease while working in Liberia for a Christian aid group.

infect with 把…传染给…; 使充满（某种感情）
例句：Mosquitoes infect human beings with malaria 
蚊子传染虐疾。 

3. Very little of the serum is available at this time.

at this time 此时此刻
例句：The answer at this time must be a qualified. 
目前的答案必然是有保留的。 

4. A number of other people were wounded.

a number of 许多的; 一些
例句：John has a number of nagging worries. 
约翰有不少牵肠挂肚的心事。