secondary source of infection

例句：

1. 1. The patient's immune system is compromised due to the secondary source of infection.
   由于次要感染源，患者的免疫系统受到了损害。
2. 2. The research team identified several potential sources of contamination in the laboratory environment.
   研究团队在实验室环境中发现了几个潜在的污染源。
3. 3. The doctor advised against using the same needle for multiple injections as it could be a secondary source ofinfection.
   医生建议不要使用同一针头进行多次注射，因为这可能会成为感染的次要来源。