[The cohort study on inapparent infection of HFRS in population of Apodemus-type endemic area and in that of Rattus-type endemic area].

Between 1988 and 1990, the positive seroconversion rates of HFRS were tested with a random sample of 7,145 persons in Apodemus-type endemic area and Rattus-type endemic area(type A; type R) in Shandong Province. The results showed that: (1) the highest positive seroconversion rate was in the group of peasants of 20 to 49 years of age in the area of type A; (2) in the area of type R, there was no statistically significant difference in positive seroconversion rates of age, and housewives had the highest rate. The male/female ratio was 2.1-2.2:1 and 0.9:1, respectively in the two types of endemic area. The ratio of apparent infection to inapparent infection was 1:22.6 and 1:42, respectively in the two types of area. It is concluded that inapparent infection is dominant in HFRS infection and there are probably many potential inapparent infections among the population.