Plague is a category A infectious disease caused by the bacterium Yersinia pestis. Plague is mostly transmitted via the rat-flea-human route, which means that fleas on rats bite rats and then bite humans, and this transmission is more frequent. It can also be transmitted through human skin to glandular plague, through the respiratory tract to cause pneumonic plague, and Yersinia pestis in the sputum of plague patients can constitute human-to-human transmission via droplets. The human population is universally susceptible to Yersinia pestis, with no differences in age or sex. Yersinia pestis is a Gram-negative coccus, newly isolated with US blue or Kimsa stain, it will show both ends with dense staining and pods, both aerobic and anaerobic bacilli, the suitable temperature is 27-28℃, so Yersinia pestis is very resistant to the outside world.