Guest appearance refers to smallpox. Liu Shi Xie Houyu: Being alone-scary. Please read it out in Liushi dialect to scare people. )

Smallpox is extinct now, but smallpox was basically a terminal disease in the past. Until now, there is no definite and effective treatment for smallpox. Humans have been vaccinated since childhood, thus eliminating smallpox. People over the age of 30 now have a "vaccinated" scar on their arms, which was the smallpox vaccine of that era.

Because smallpox is so terrible, people around Liushi dare not say smallpox. They all say it's a doctor, which means they left as soon as they were diagnosed.