伝染

1. Origins, structure, and basic meaning

• Structure: 伝染 is read as でんせん and works as a noun or with する for a disease or reaction spreading from one person to another.
• Basic usage: Use 病気の伝染を防ぐ for disease transmission and 笑い声が皆に伝染する figuratively for laughter spreading through a group.

2. Common pitfalls and similar expressions

• Literal and figurative use
  • Disease transmission is a core use, but the word can figuratively describe a mood or reaction such as laughter passing among people.
• Focus versus 感染
  • 感染 often focuses on an individual or cells becoming infected, while 伝染 readily focuses on spread between people.