Why do some people say that the Jin Dynasty died of the "Bianjing Plague", and how was this plague triggered?

In the battle of Bianjing, the Jin defeated the Mongols and held Bianjing City. But not long after, the "Bianjing plague" broke out in an all-round way, which indirectly led to the demise of the Jin Dynasty. So how did this plague happen? I think there are several reasons.

The first one: the decay of a large number of dead people

With the coming of the war, soldiers died constantly, and during the war, the city gate was closed, so it was impossible to pull a large number of the dead out of the city for proper handling. With the continuous accumulation of the dead and the continuous breeding of bacteria, the epidemic situation appeared and the situation was out of control.

Second, soldiers have low immunity and poor medical conditions.

War is a huge consumption for a country, and it is also for soldiers. The war has caused losses to the original Qiang Bing, not to mention the situation of the old, the young and the sick in the war. Coupled with the poor medical level at that time, the epidemic could not be effectively controlled in a short time, and many people could only wait for death.

Third: Bianjing City is crowded and dirty.

Before the Mongols attacked Bianjing, the Jin people ordered all the soldiers and civilians outside the city and their families to move to Bianjing with rations in order to ensure the supply of food and grass, and the population once surged. In today's words, population explosion means ecological imbalance, and crowded population, dirty sanitation and war have created good conditions for the plague.