They did not know how HIV spreads through blood, through body fluids during sex and breastfeeding, and through drug injections.

他们不知道艾滋病毒是如何通过血液、性行为和母乳喂养过程中的体液以及注射毒品传播的。

Other causes are swelling of the tissue after severe burns, intravenous drug injection, repetitive use of the injured muscles or a vigorous muscle contraction, like in a tetany or seizures.

其他原因包括严重烧伤后组织肿胀、静脉药物注射、反复使用受伤的肌肉，或肌肉剧烈收缩，如手足搐搦或癫痫。