The features of imported dengue fever cases from 1996 to 1999.

four grades, from less severe (grade I) to severe (grade 4). Grades 3 and 4, in which plasma leakage is so profound that shock occurs,arealSo referred to as dengue shock syndrome (DSS) (3). Dengue virus infections are a serious cause of morbidity and mortalityin many areas of the world: Southeastand South Asia, Central and SouthAmerica, the Caribbean,and Africa. It is estimated that 100 million cases of dengue fever and 250,000 cases of DHF occur annually (4). Thus, DF/DHF is one of the most important infectious diseases in the world. The regions in which dengue virus infectionsare shown to be serious health problems have been expanding,and the number of DHF cases is increaslng. The World Health Organization reports that domestic dengue virus infections occur in nearly 100 countries and reglOnS. A dengue outbreak occumd in Osaka, Robe, Hiroshima, and Nagasaki from 1942 to 1945, and dengue viruStype I was responsible for the outbreak (5). Dengue virus infections have never reached epidemic proportions in Japan sincethen, and there are currently no domestic dengue virus infections in contemporary Japan. However, imported dengue cases have been reported (6). We have beenperforming serodiagnosis of dengue virus infection upon request from hospitals and clinics. The features of imported dengue cases that we serodiagnosed from 1985 to 1995 at the Department of Virology 1 , National Institute of Infectious Diseases, Japan (NIID) were previously reported (6)・ Serum speclmenS Were Obtained from dengue-suspected cases in clinics and hospitals in Japan from 1996 to 1999, and were sent tothe Department of Virology 1, NIID for the laboratory diagnosis of dengue. In the present manuscript, We reprt features of these dengue cases. Dengue virus infections were diagnosed by lgM-capture enzyme-linked immunosorbent assay (ELISA), reverse transcriptase-polymerase chain reaction (RTIPCR), and hemmagglutination inhibition (HI) test,