AIDS=Acquired Immune Deficiency Syndrome 获得性免疫缺损综合征
HIV is a virus that attacks the immune system, our body's natural defence against illness.
艾滋病毒是一种攻击免疫系统的病毒，免疫系统是我们身体抵抗疾病的天然防御。
If HIV is left untreated, a person's immune system will get weaker and weaker until it can no longer fight off life-threatening infections and diseases.
如果不对艾滋病病毒进行治疗，那么一个人的免疫系统就会变得越来越弱，直到它再也无法对抗危及生命的感染和疾病。

immune system 免疫系统

life-threatening 可能致命的；威胁着生命的。
His heart condition is not life-threatening.
他的心脏病不会致命。
Doctors say that his condition isn't life-threatening.
医生说他的情况没有生命危险。

infection 传染，感染
have an infection 感染了
I think you've got a nasty throat infection, so you need to rest.
我觉得你应该是喉咙感染了，你要休息一下。

treat an infection 治疗感染
Antibiotics are used to treat the infection.
抗生素是用于治疗感染的。

spread an infection 传染疾病

How AIDS spreads 艾滋病是怎样传播的
This can happen in several ways: 传播可以通过以下几种方式：
By having sex. 性交。
From blood transfusions. 输血。
By sharing needles. 公用针头。
During pregnancy or delivery or through breast-feeding. 通过怀孕、生产、母乳喂养。（母体传染）