Abstract: Objective To explore the epidemic rule of HFRS.Methods In 1983-1998,little beasts including rats were supervised in various items in Zhuyi county and Shiqian county etc.Results The surveillant results showed that infectious areas of the wild and domestic rat types of HFRS assume various forms:the wild,the house-rat and both mixed types.Infectious areas rely on relative stability of Apodemus agrarius and R.norvegicus in specific host animal and reservoir.When geographic scenes obviously change,the effect of natural defence weakened or disappeared and infectious area evolved obviosly fast.Conclusion The exploited area of original forest in Kuan Kuo Shui,Shui Yang County maybe became a new infectious area.Infectious areas of the wild rat type in Luo Wang river,Kai Yang county expanded to neighboring house rat becoming mixed infectious area one on top of another.The phenomenon maybe indicate a type of evolution of infectious area.