1. any disease easily transmitted by contact

2. an incident in which an infectious disease is transmitted

3. the communication of an attitude or emotional state among a number of people;

   "a contagion of mirth"
   "the infection of his enthusiasm for poetry"
   

1.接触传染
contagion is the spreading of a particular disease by someone touching another person who is already affected by the disease.

e.g. They have been reluctant to admit AIDS patients, in part because of unfounded fears ofcontagion...
他们一直不愿接纳艾滋病患者，部分原因是无来由地害怕被接触传染。
e.g. I'm a blood donor; I can't risk anycontagion.
我是献血者，我不能冒任何接触传染的危险。

2.(不良思想、态度、感情等的)传播，蔓延
You can usecontagion to refer to the spreading of ideas, or attitudes, or feelings that you consider to be bad or unacceptable from one group of people to another.

e.g. He continues to insulate his country from thecontagion of foreign ideas.
他继续使本国远离外来思想的侵袭。

3.接触传染病
Acontagion is a contagious disease.

1. 感染：旨在揭示集体行为的理论可分为三类:第一类理论(如勒邦的理论),根据感染(contagion),情绪的迅速传播以及不加批判地接受指挥等来解释行为;第二类理论用具有相似的预先倾向、观念和目标的人们的趋同现象(convergence)来描述集体行为;

2. 传染病：contact 接触,联系 vt.与...接触,使联系 |contagion 传染(病) | contagious 传染的,有感染力的