ひよりみかんせんしょう
日和見感染症
Opportunistic infection
健康な人には感染症(infectious disease)を起こさない菌が原因となって、免疫力(immunity / immune system resistance to illness)が低下した人に発症する感染症のこと。
This refers to an infectious disease that occurs in people with weakened immune systems, which is caused by a germ that wouldn’t cause an infection in a healthy person.