Figure 2  Immunofluorescence assay of serum samples, COVID-19 index case, Finland, January–February 2020
COVID-19: coronavirus disease 2019.
Anti-SARS-CoV-2 IgM and IgG antibodies were detectable by immunofluorescence assay in samples from Days 9, 10 and 20 after onset of illness. Both IgM and IgG were found at a titre of 80 on Day 9, titres on Day 20 were 320 and 1,280. As an example, dilutions 1:20 and 1:160 from the Day 20 sample are shown for, respectively, IgM and IgG of the index case. Dilution 20 shown for the control serum.