There were many reasons for the outbreak of the plague on White Deer Plain. For details, you can refer to the following possible reasons: 1. Soil pollution: The soil in the White Deer Plain area contains harmful substances such as heavy metals and organic matter. If these substances are not handled properly by human activities, they may cause the spread of diseases. 2. Transmission by wild animals: The White Deer Plain area is the habitat of wild animals, including deer, wild boars, etc. These wild animals may carry diseases. If humans come into contact with or eat infected animals, it may lead to the transmission of diseases. 3. Water pollution: The water sources in the White Deer Plain area may be polluted. For example, drinking water sources may be polluted by harmful substances such as pesticides and heavy metals, which may cause human infection. 4. Outbreak of disease: There have been some outbreak of diseases in the White Deer Plain area, such as plague, black death, etc. The pathogen of these diseases may exist in the animals or humans in the White Deer Plain area, causing the spread of diseases. There were many reasons for the outbreak of the plague in the White Deer Plains. It might involve the environment, animals, humans, and many other factors.