Table 3. Characteristics of the main cusses of fever postoperatively during the outbreak period of coronavirus disease 2019 (COVID-19) infection.

Causes	Time (days)	Typical clinical feature
Non-infectious postoperative fever	<2	(I) Fever;
		(II) Normal WBC count, CRP and PCT levels;
		(III) Normal chest imaging;
		(IV) Viral nucleic acid test result negative
Surgical site infection	>3	(I) Chills, rigors, fever, purulent drainage;
		(II) Elevated WBC count, CRP and PCT levels;
		(III) Normal chest imaging;
		(IV) Viral nucleic acid test result negative
Lung diseases
Atelectasis	<2	(I) Fever, dry cough, hypoxemia, dyspnea;
		(II) Normal WBC count, CRP and PCT levels;
		(III) Uniform ground glass opacity;
		(IV) Viral nucleic acid test result negative
Bacterial pneumonia	>2	(I) Fever, chills, rigors, cough, expectorations);
		(II) Elevated WBC count, CRP and PCT levels;
		(III) Infiltrative shadow, consolidation;
		(IV) Viral nucleic acid test result negative
COVID-19 infected pneumonia	1–24 [5]†	(I) Fever, dry cough, fatigue;
		(II) Lymphopenia, decreased or normal WBC count;
		(III) Bilateral patchy shadows or ground glass opacity;
		(IV) COVID-19 viral nucleic acid test result negative

^†, the number is recorded as incubation period. COVID-19, coronavirus disease 2019; CRP, C-reactive protein; PCT, procalcitonin; WBC, white blood cell.