Table 1.

Etiology of COVID-19-negative cases

Etiology	Number of patients
Bacterial infection	33
Mycobacterium tuberculosis complex	2
Influenza virus A	2
Influenza virus B	1
Influenza virus B and mycoplasma	2
Mycoplasma	1
Undetermined*	39
Total	80

*13 patients had negative respiratory tract IgM including legionella type 1; mycoplasma; Coxiella burnetii; Chlamydia pneumoniae; adnovirus; R syncytial virus A and B (RSVA and RSVB); influenza virus A and B (FluA and B); parainfluenza virus 1, 2, 3, and 4 (PIV1, 2, 3, and 4); coronavirus OC43 type; coronavirus 229E/NL63 type; human metapneumovirus (HMPV); human rhinovirus (HRV); enterovirus (EV); and human bocavirus (H BoV). And the other 26 patients had negative FluA and B IgM