Epidemiological progresses of hemorrhagic fever with renal syndrome in China.

PURPOSE: To summarize the major achievements of Chinese work on the epidemiology and prevention of hemorrhagic fever with renal syndrome (HFRS) in recent 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 of 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 specially assessed.
RESULTS: HFRS was first recognized in the northeastern China in 1931. It has been found prevalent also in many other parts of China since 1955, and presently, 28 out of 31 provinces (autonomous regions, or municipalities) have been proved to be its endemic areas. The total number of cases is 1,256,431 from 1950 to 1997, with 44,304 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 (115,985 cases). Three types of endemicity have been differentiated: the Apodemus-type, the Rattus-type and the mixed type of the two, by their peculiar seasonal distributions of cases and by methods of serotyping (HI, MAbs serotyping kits). The epidemiologic features of the Rattus-type HFRS are quite different from that of the Apodemus-type. 67 species of vertebrates were found to harbor hantavirus antigen or antibodies, but the chief or primary reservoir hosts are Apodemus agrarius and Rattus norvegicus only. Besides the commonly recognized enzootic mode of transmission (via contacts with the reservoir rodents or their excreta), mite transmission (including certain species of gamasid mites, and chigger mites) has been identified as the potential vectors and reservoir hosts with HFRS. Vertical transmission had been found in pregnant patients with HFRS, and in all three chief host rodents (Apodemus agrarius, Rattus norvegicus, the laboratory rats). The relatively high inapparent infection rates in the population of endemic areas of the Rattus-type HFRS after big outbreaks (8%-20%) are suggested to play a significant role in the gradual decline of the incidence of HFRS in that areas. Three kinds of inactivated vaccines against HFRS (the golden hamster kidney cell vaccine, the Mongolian gerbil kidney cell vaccine and the purified suckling mouse brain 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 China have accomplished great achievements since 1981. As the relatively high annual incidence of HFRS sustained in recent years, control measures have to be reinforced. Many problems of HFRS and hantavirus infections are still not well understood or unclear, such as the poly-host nature, and the multi-modes of transmission, the natural history of hantaviruses and their genetic variation occurred in nature etc. The task for effective control of HFRS and the research on its epidemiology in China should be held on a high priority.