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

  Objective   To analyze dynamic rules of SARS coronavirus(SARS-CoV)IgG antibody of probable patients with severe acute respiratory syndrome(SARS)during the epidemic period in 2003 and whether the asymtomatic infections existing in healthy population from several areas.

  Methods   Indirect immunofluo rescent assay(IFA)and double-antigen sandwich enzyme-linked immunosorbent assay(ELISA)were used to detect the SA RS coronavirus-specific IgG antibodies in serum specimens, including 1453 healthy persons from Hongkong, Marco, Guangzhou and Peking and 257 SARS probable patients from Guangzhou and Peking.The dynamics of the serum antibodies of SARS patients were observed from 3 to 270 days after onset of symptoms.

  Results   Among healthy persons including 160 close contacters of SARS patient, only 2 were positive by the sandwich EL ISA.These two specimens were negative by IFA.90% of 257 patient serum specimens after 20 days of disease onset showed positive SARS-CoV IgG either using ELISA or IFA.Of 257 SARS patients, 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 the titers for two months.Then antibody titers declined in some cases.How ever, all specimens still were positive for SARS-CoV IgG in the 9th month of the disease onset.

  Conclusion   Few asymtomatic infectious patients may exist during SARS epidemic.Serum IgG antibody has diagnostic value for SARS in the late course of the disease and the antibodies present more than 9 months.