Epidemiological progresses of hemorrhagic fever with renal syndrome in China

Purpose To summarize the major achievements of Chinese work on the epidemio logy and prevention of hemorrhagic fever with renal syndrome (HFRS) in rece nt years, and to give a general review on the present situation of HFRS in China. Data sources Reviews and papers published in Chinese journals, relevant to the objectives, written or collected by the author; and the research work o f the author. Study selection An outline was drafted according to the purpose given above , and the relevant materials and data were grouped together into different items outlined. Data extraction All the materials and data extracted were published or spec ially assessed. Results HFRS was northeastern China in 1931. It has been found prevalent al so in many other parts of China since 1955, and presently, 28 out of 31 pro vinces (autonomous regions, or municipalities) have been proved to be its e ndemic areas. The total number of cases is 1256431 from 1950 to 1997, with 44304 death (3.53%). 50-100 thousands of cases could be registered annually since 1981 when the presence of the Rattus-type HFRS was first identified serologically in China, with the highest peak in 1986 (115985 cases). Three types of endemicity have been differentiated: the Apodemus-type, the Rattu s-type and the mixed type of the two, by their peculiar seasonal distributi ons of cases and by methods of serotyping (HI, MAbs serotyping kits). The e pidemiologic features of the Rattus-type HFRS are quite different from that of the Apodemus-type. 67 species of vertebrates were found to harbor hanta virus antigen or antibodies, but the chief or primary reservoir hosts are A podemus agrarius and Rattus norvegicus only. Besides the commonly recognize d enzootic mode of transmission (via contacts with the reservoir rodents or their excreta), mite transmission (including certain species of gamasid mi tes, and chigger mites) has been identified as the potential vectors and re servoir hosts with HFRS. Vertical transmission had been found in pregnant p atients with HFRS, and in all three chief hose rodents ( Apodemus agrarius, Rattus norvegicus, the laboratory rats). The relatively high inapparent: i nfection rates in the population of endemic areas of the Rattus-type HFRS a fter big outbreaks (8% - 20%) are suggested to play a significant role in t he gradual decline of the incidence of HFRS in that areas. Three kinds of i nactivated vaccines against HFRS (the golden hamster kidney cell vaccine, t he Mongolian gerbil kidney cell vaccine and the purified suckling mouse bra in vaccine) have been successively developed and proved highly effective in the prevention of HFRS. Conclusion Chinese workers on the epidemiology and prevention of HFRS in Ch ina have accomplished great achievements since 1981. As the relatively high annual incidence of HFRS sustained in recent years, control measures have to be reenforced. Many problems of HFRS and hantavirus infections are still not well understood or unclear, such as the poly-host: nature, and the mul ti-modes of transmission, the natural history of hantaviruses and their gen etic variation occurred in nature etc. The task for effective control of HF RS and the research on its epidemiology in China should be held on a high p riority.