嚴重急性呼吸系統綜合症
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, the virus causing COVID-19) sometimes does not follow the usual pattern, with IgM sometimes occurring after IgG, together with IgG, or not occurring at all. Generally however, median IgM detection occurs 5 days after symptom onset, and IgG is detected a median 14 days after symptom onset.