Remarks: The World Health Organisation states that a Rat-flea Index greater than 1 represents an increased plague risk for humans if the plague bacillus was introduced into a territory.

• 注:世界衞生组织指出,鼠蚤指数高于1的地区如出现鼠疫杆菌,鼠疫传染给人类的风险便会增加。