Plague is an infectious disease caused by the bacterium Yersinia pestis and is mainly transmitted to humans by fleas from rodents.

Plague has existed since ancient times and once caused large-scale epidemics in Europe, such as the Black Death in the 14th century.

Yersinia pestis is a gram-negative bacterium, a genus in the family Coccaceae.

There are two main subspecies of Yersinia pestis: Yersinia pestis subspecies pestis and Yersinia pestis subspecies Tanga.

This bacterium primarily lives in mice and other rodents and is transmitted to humans through fleas.

Plague is spread mainly through the bites of fleas carrying Yersinia pestis.

When an infected rodent dies, the fleas can infect other rodents or humans.

Plague can also be spread through the air or through direct contact with the body fluids of a sick person.

The clinical manifestations of plague can be divided into three types: bubonic plague, pneumonic plague and sporadic plague.

Bubonic plague mainly manifests itself as swollen and painful lymph nodes, and the skin may also appear red, swollen and gangrene.

Pneumonic plague can cause severe respiratory symptoms such as coughing, sputum production, and difficulty breathing.

Sporadic plague is the rare but most severe form, with symptoms including high fever, weakness and systemic organ failure.

Plague prevention mainly includes preventing the breeding and spread of rodents and preventing flea bites.

Public health departments should strengthen environmental sanitation management to reduce the breeding and spread of rodents and fleas.

Vaccination is also an important measure to prevent plague.

Plague outbreaks can have serious social and economic impacts.

Plague outbreaks require quarantine and lockdown measures, which impose great restrictions on people's lives and economic activities.

Plague can also have a major impact on tourism and trade, leading to a reduction in international exchanges.