Seroprevalence of COVID-19 virus infection in Guilan province, Iran
Background: The extent of infection by coronavirus disease 2019 has not been well documented. In this study we aimed to determine seropositivity of COVID-19 virus infection in population of a highly affected area in north of Iran. Methods: In a population-based cluster random sampling design through phone call invitation, a total of 196 household including 552 subjects agreed to participate in this study. Each participant were taken 50ml blood sample at health care center. Rapid test kits were used to detect antibody against COVID-19. Crude, population-weight adjusted and test performance adjusted prevalence of antibody seropositivity to SARS-CoV-2 were reported. Results: The prevalence of antibody seropositivity was 0.22 (95%CI: 0.19-0.26). The population weight adjusted estimate was 0.21 (95%CI: 0.14-0.29) and test performance adjusted prevalence was 0.33 (95%CI: 0.28-0.39). Based on these estimates the range of infected people in this province would be between 518000 and 777000. Conclusion: The population seropositivity prevalence of COVID-19 virus infection indicated that the asymptomatic infection is much higher than the number of confirmed cases of COVID-19. This estimate can be used to better detect infection fatality rate and decide for public policy guidelines.