Emerg Infect Dis. 2020 Aug 28;26(12). doi: 10.3201/eid2612.203334. Online ahead of print.
Among patients with coronavirus disease (COVID-19), IgM levels increased early after symptom onset for those with mild and severe disease, but IgG levels increased early only in those with severe disease. A similar pattern was observed in a separate serosurveillance cohort. Mild COVID-19 should be investigated separately from severe COVID-19.