Seroepidemiological study On SARS-CoV IgG antibody of different populations from several areas

Objective To analyze dynamic rules of SARS coronavirus( S ARS-CoV) IgG antibody of probable patients with severe acute respiratory syndrom e(SARS) during the epidemic period in 2003 and whether the asymtomatic infection s existing in healthy population from several areas. Methods Indirect immunofluorescent assay(IFA) and double- antigen sandwich enzyme-linked immunosorbent assay (ELISA) were used to detect t he SARS coronavirus-specific IgG antibodies in serum specimens,including 1453 he althy persons from Hongkong,Marco,Guangzhou and Peking and 257 SARS probable pat ients from Guangzhou and Peking.The dynamics of the serum antibodies of SARS pat ients were observed from 3 to 270 days after onset of symptoms. Results Among healthy persons including 160 close contact ers of SARS patient,only 2 were positive by the sandwich ELISA.These two specim ens were negative by IFA.90% of 257 patient serum specimens after 20 days of dis ease onset showed positive SARS-CoV IgG either using ELISA or IFA.Of 257 SARS pa tients,antibody titers increased steadily in early 4 to 6 months after onset of SARS.The titers of most cases came to the peak in the 6th month and maintained t he titers for two months. Then antibody titers declined in some cases.However,a ll specimens still were positive for SARS-CoV IgG in the 9th month of the diseas e onset.Conclusion Few asymtomatic infectious patients may exist during SARS epidemic.Serum IgG antibody has diagnostic value for SARS in the lat e course of the disease and the antibodies present more than 9 months.