表示“发生、传播”意义的动词,如happen,take place,break out,spread等,常用主动形式表示被动意义.如：
The news spread in a small village.
消息在一个小村庄传开了.
但是spread确实又有被动的时候,强调由谁传播的时候用
比如
It spreads easily through direct contact among animals,it is also spread by people on clothing and shoes.