Three months after a coronavirus disease (COVID-19) outbreak in Kupferzell, Germany, a population-based study (n = 2,203) found no RT-PCR-positives. IgG-ELISA seropositivity with positive virus neutralisation tests was 7.7% (95% confidence interval (CI): 6.5-9.1) and 4.3% with negative neutralisation tests. We estimate 12.0% (95% CI: 10.4-14.0%) infected adults (24.5% asymptomatic), six times more than notified. Full hotspot containment confirms the effectiveness of prompt protection measures. However, 88% naïve adults are still at high COVID-19 risk.
Keywords: COVID-19; SARS-CoV-2; antibody; seroepidemiologic studies; seroprevalence.