COVID-19 or non-COVID viral pneumonia: How to differentiate based on the radiologic findings?

Table 1 Clinical features of coronavirus disease 2019 and influenza A[11,18,20-27]

	COVID-19	H1N1
Fever	++++	++++
Cough	+++	++++
Myalgia	++	++
Fatigue	++	++
Sputum	++	++
Rhinorrhea	+	++
Dyspnea	++	++
Headache	++	+
Nausea & Vomit	+	+
Chest pain	+	+
Sore throat	+	++
Diarrhea	+	+
Hemoptysis	+	+
Skin lesions	Erythematous rash, urticarial, chickenpox-like vesicles (+)[28]	Maculopapular (+)[29]
Conjunctivitis	+[30]	+[31]
Other eyes lesions	-	Sub conjunctival hemorrhage, uveal affection, retinopathy, and optic neuritis (+)[32]
Anosmia, hyposmia	+/++[33,34]	+[35]
Ageusia, dysgeusia (loss of taste)	+[34]	+[36]
Transmission interval	5-6 d	3 d
Reproductive number	2.2	1.3-1.7

+: Rare; ++: Uncommon; +++: Common; ++++: Very common; COVID-2019: Coronavirus disease 2019; H1N1: Influenza A.

Table 2 Comparison of chest computed tomography findings of coronavirus disease 2019 and influenza A[18,43,47-51,53-73]

	COVID-19	H1N1
GGO	++++	+++/++++
Unilateral distribution	-/+ (++ in asymptomatic patients)	+
Bilateral distribution	++++	+++/++++
Posterior distribution1	++++	N/A
Peripheral distribution1	+++/++++	++
Multi-lobar distribution	++++	+++
Mixed (peripheral and central) distribution	++	+++
Pure GGO1	++/+++	+/++
Clear margin GGO	++	+
Cluster GGOs around bronchial tree1	+	+++
Patchy GGO	+++	++
GGO with consolidation	++/+++	+++
Pure consolidation	+/++	++/+++
Reticulation (linear opacities)	++/+++	++/+++
Subpleural curvilinear line1	+	N/A
Rounded opacities	++	++
Crazy paving	++	+/++
Halo sign	-/+	-/+
Air space nodules1	+	+/++
Tree-in-bud1	-/+	++
Air bronchogram	+/++ (in later stages)	++
Interstitial septal thickening	+/++ (increased in later stages)	+/++
Bronchiolar wall thickening	++	+/++
Pleural effusion1	-/+	++
White lung (ARDS)	+/++	+/++ in general (+ in mild, ++ in moderate and+++ in severe influenza)
Fibrotic bands	+/++ (in late stages)	+ (++ for H7N9)
Melted sugar sign1	++	N/A
Air way secretions	-/+	N/A
Lymphadenopathy	+	+
Bronchiectasis	-/+	+
Intra-lesional vascular enlargement1	++/+++	N/A
Bronchial wall thickening	+	+
Focal pleural thickening	+/++	+/++
Pericardial effusion	-/+	-/+
Bronchiectasis	-/+	+
Reverse halo sign	+	-/+
Pneumothorax	-/+	-/+
Cavitation	-	-/+

¹Important distinguishing features. -: None; -/+: Few cases; +: Some cases; ++: Fairly typical; +++: Common; ++++: Very common; N/A: Not available data; COVID-2019: Coronavirus disease 2019; H1N1: Influenza A; GGOs: Ground glass opacities.