Abstract：Aim Research about the detection of IgM antibody in patients wioh Dengue fever with by IFAT. Method During dengue fever epidemics(serotype ) occurred in Guangdong Province from July to November 1995.62 sera were collected within 17 days of disease onset from the suspected patients for detection of dengue fevers IgM antibody by IFAT. Result The positive rate was 24.19%(15/62) and the highest rate was in 45 days of diseases onest with positive rate40.00%.The IgM titer was between 110140,and most of them was 110(8/15).The crossreactions was found in sera from the patients with encephalitis,but not from other nondenguefever sera.IgM and IgG antibodies could bedetected at the sametime from the 56 th day sera. Conclusions The sera within 13 days of disease onset can be used for virus isolation,and between 46 days for IgM detection.If negative IgG detection should be futher carried on,so as to improve dengue fever detectoin rate
