The key populations as defined by the study are the people who are mainly drug injectors, men who have sex with men, and sex workers.

VOA: standard.2010.07.07

The study of immunology is the study of mechanisms that your body uses to protect itself from mainly from foreign pathogens like viruses and bacteria.

免疫学研究身体,采用何种机制来保护自身,免受外源病原体如病毒和细菌的伤害

耶鲁公开课 - 生物医学工程探索课程节选

The study of immunology is the study of mechanisms that your body uses to protect itself from mainly from foreign pathogens like viruses and bacteria.

免疫学研究身体,采用何种机制来保护自身,免受外源病原体如病毒和细菌的伤害

耶鲁公开课 - 生物医学工程探索课程节选