My sister-in-law is a very kind person.

Where is your sister?

Where does your younger sister live?

She is my sworn younger sister, and we are always together.

A ping-pong infection occurred at school, causing many students to take time off.

Oral infection is when pathogens enter the body through food or drink.

Prevention of infectious diseases is important with hand washing and wearing masks.

Due to the increase in community-acquired infections, please thoroughly wash your hands and wear masks.

Please refrain from going out because community-acquired infections are spreading rapidly.

It is important to identify the source of infection.