Seroprevalence and epidemiological characteristics of immunoglobulin M and G antibodies against SARS-CoV-2 in asymptomatic people in Wuhan, China

ObjectivesPopulation screening for IgG and IgM against SARS-CoV-2 was initiated on March 25 and was open to all residents of Wuhan who were symptom-free. All ages with no fever, headache or other symptoms of COVID-19 among residents in Wuhan were included. MethodsThis study adopted a cross-sectional study. Pearson Chi-square test, T-test, and Mann-Whitney test were used in comparison between different groups. To correct the effects of gender and age, the seroprevalence of IgM positivity, IgG positivity, and IgM and/or IgG positivity were standardized according to the gender and age-specific population of Wuhan in 2017. ResultsThe seroprevalence of IgG and IgM standardized for age and gender in Wuhan showed a downward trend. No significant correlation was observed between the seroprevalence of IgG and the different age groups. The seroprevalence was significantly higher for females than males (x2 =35.702, p < 0.001), with an odds ratio of 1.36 (95% CI: 1.24-1.48). A significant difference was seen in the seroprevalence of IgG among people from different geographic areas and different types of workplaces (respectively, x2 = 42.871, p < 0.001 and x2 = 202.43, p < 0.001). The IgG antibody-positive cases had a greater number of abnormalities in CT imaging than IgG-negative cases (30.7% vs 19.7%). ConclusionsOur work found the reported number of confirmed patients in Wuhan only represents a small proportion of the total number of infections. There was a significant aggregation of asymptomatic infections in individuals from some occupations, and based on CT and laboratory findings, some damage may have occurred in asymptomatic individuals positive for IgG antibody. O_LSTStrengths and limitations of this studyC_LSTO_LIThis study has the important feature of having been designed as repeated five-day serosurveys, which allowed for the monitoring of seroprevalence progression. C_LIO_LIThis study applied scientific statistical methods accounting for the demographic structure of the general population and imperfect diagnostic tests to estimate seroprevalence in the overall population. C_LIO_LIThis study had selection bias since the analyzed medical records were based on examinees directed by their work units. C_LIO_LIPeople under the age of 19 and over age 65 were too few to be fully covered in analyses. C_LI