Due to only around 50% positive rate of SARS‐CoV‐2 nucleic acid test8, 12 under various condition of sample collection and storage, viral infection regions, RNA extraction methods, the quality of nucleic acid detection kit, and so on,13 detection of IgM/IgG became a powerful approach for the early diagnosis of COVID‐19 and could help identify the patients with negative nucleic acid but with obvious clinical symptoms.8, 14. This evidence concerns the gene CD40LG and viral infectious disease.