BJR https://​doi.​org/​10.​1259/​bjr.​20200515 © 2020 The Authors. Published by the British Institute of Radiology under Received: Revised: Accepted: the terms of the Creative Commons Attribution 4.0 Unported License 05 May 2020 08 June 2020 18 June 2020 http://​creativecommons.​org/​licenses/​by/​4.​0/, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited. Cite this article as: Franquet T, Jeong YJ, Lam HYS, Wong HYF, Chang Y-­C, Chung MJ, et al. Imaging findings in coronavirus infections: SARS-­CoV, MERS-­ CoV, and SARS-­CoV-2. Br J Radiol 2020; 93: 20200515. Pictorial Review Imaging findings in coronavirus infections: SARS-­CoV, MERS-­CoV, and SARS-­CoV-2 1 Tomas Franquet, 2Yeon Joo Jeong, 3Hiu Yin Sonia Lam, 3Ho Yuen Frank Wong, 4Yeun-­Chung Chang, 5 Myung Jin Chung and 5Kyung Soo Lee, MD, PhD 1 Department of Radiology, Hospital de Sant Pau. Universidad Autónoma de Barcelona, Barcelona, Spain 2 Department of Radiology and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea 3 Department of Radiology, Queen Mary Hospital, Hong Kong, China 4 Department of Medical Imaging, National Taiwan University Hospital and Department of Radiology, National Taiwan University College of Medicine, Taipei, Taiwan 5 Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine (SKKU-­SOM), Seoul, Korea Address correspondence to: Dr Kyung Soo Lee E-mail: ​kyungs.​lee@​samsung.​com The authors Tomas Franquet and Yeon Joo Jeong contributed equally to the work. Abstract: During the first two decades of the 21st century, there have been three coronavirus infection outbreaks raising global health concerns by severe acute respiratory syndrome coronavirus (SARS-­CoV), the Middle East respiratory syndrome coronavirus (MERS-­CoV), and the SARS-­CoV-2. Although the reported imaging findings of coronavirus infection are variable and non-­specific, the most common initial chest radiograph (CXR) and CT findings are ground-­glass opacities and consolidation with peripheral predominance and eventually spread to involve both lungs as the disease progresses. These findings can be explained by the immune pathogenesis of coronavirus infection causing diffuse alveolar damage. Although it is insensitive in mild or early coronavirus infection, the CXR remains as the first-­line and the most commonly used imaging modality. That is because it is rapid and easily accessible and helpful for monitoring patient progress during treatment. CT is more sensitive to detect early parenchymal lung abnormalities and disease progression, and can provide an alternative diagnosis. In this pictorial review, various coronavirus infection cases are presented to provide imaging spectrums of coronavirus infection and present differences in imaging among them or from other viral infec- tions, and to discuss the role of imaging in viral infection outbreaks. Introduction humoral and cellular immunity (Figure 1). Coronavirus In late December 2019, the 2019 novel coronavirus pneu- induces lung injury by involving angiotensin converting monia caused by severe acute respiratory syndrome coro- enzyme, by cell apoptosis induced by specific viral proteins, navirus 2 (SARS-­CoV-2) occurred in Wuhan, China, and and by cytokine storm, the uncontrolled systemic inflam- has spread quickly worldwide. During the first two decades matory response resulting from the release of large amounts of the 21st century, there have been three coronavirus of pro-­inflammatory cytokine and chemokines1 (Figure 1). infection outbreaks raising global health concerns by the It has been reported that CT patterns of pulmonary viral SARS-­CoV, the Middle East respiratory syndrome corona- infection are related to their pathogenesis and most viral virus (MERS-­CoV), and the SARS-­CoV-2 (the respiratory pneumonia patterns exhibit similarity based on viridae.2 disease caused by SARS-­CoV-2 is now called coronavirus Therefore, the imaging findings of coronavirus infection disease-19, COVID-19). Coronaviruses are enveloped caused by SARS-­ CoV, MERS-­ CoV, and SARS-­ CoV-2 viruses with a positive-­sense single-­stranded RNA genome closely resemble each other. The purpose of this pictorial and have club-­ shaped surface-­ spike glycoprotein which review is to provide imaging spectrums of coronavirus plays an important role in binding to receptors on host cells. infection and present differences in imaging among them After the virus enters the cells, its antigen is presented to dendritic cell or macrophage, which stimulates the body’s BJR Franquet et al Figure 1. Immune-­ pathogenesis of coronavirus infection. To Table 1. Epidemiology and clinical characteristics of human enter into host cells, envelope spike glycoprotein of corona- coronavirus infection virus binds to the cellular receptor of host cells (1). After the virus enters the cells, the viral RNA genome is released and SARS-­ MERS-­ replicated (2). While the virus enters the cells, its antigen is Characteristics CoV CoV SARS-­CoV-2 presented to antigen-­presenting cell such as dendritic cell or Epidemiology macrophage (3), which migrates to regional lymph nodes and  Outbreaks (year) 2002–2004 2012, 2019–2020 stimulates the body’s humoral and cellular immunity by virus-­ 2015, specific B and T cells (4). Virus-­specific B and T cells produce 2018 antibodies and release numerous cytokines. Cytokines induce  Confirmed cases 8,422 2494 6,799,713* the recruitment of neutrophils and monocyte-­derived alveo- lar macrophage, and these amplify the inflammatory response  Death 916 858 397,388* (5). The exuberant inflammatory response can disrupt the  Mortality rates % 11 34.4 5.8* alveolar-­capillary barrier, resulting in alveolar flooding and  Age (years) 44 56 51–56 intra-­alveolar fibrin accumulation (6). Cytokine storm, which is an uncontrolled systemic inflammatory response result-  Sex ratio (male to 0.8:1 3.3:1 1.7:1 ing from the release of a large amount of pro-­inflammatory female) cytokines, causes acute respiratory distress syndrome and  Underlying diseases multiorgan failure. These immune responses result in diffuse % alveolar damage or organizing pneumonia, which are man-  Diabetes 24 36–66 11–19 ifested as ground-­glass opacity, consolidation, crazy paving appearance, and reversed halo sign with peripheral predomi-  Hypertension 19 31–65 19–30 nance on CT (7).  Cardiovascular 10 20–41 4–8 disease  Malignancy 3 2 0.5–1 Symptoms %  Fever 99–100 40–100 94  Cough 62–100 29–100 79–81  Dyspnea 40–42 48–100 40  Myalgia 45–61 32 15–32  Headache 20–56 13 10–14  Sore throat 9–25 7–83 5–8  Nausea or vomiting 20–35 21 4  Diarrhea 20–32 26 5 Laboratory findings %  Lymphopenia 65–89 34 40–65  Increased CRP 78 63 52–86  Thrombocytopenia 33–46 36 23–42  LDH elevation 56–87 49 67–98 CRP, C-­ reactive protein; LDH, lactate dehydrogenase; MERS-­CoV, Middle East respiratory syndrome coronavirus; SARS-­ CoV, severe acute respiratory syndrome coronavirus; SARS-­CoV-2, severe acute respiratory syndrome coronavirus 2. a Situation on June 07, 2020 outbreaks, the number of confirmed cases of SARS-­CoV-2 infec- tion worldwide has exceeded 6,700,000, which is about 2,700 or from other viral infections, and discuss the role of imaging in times that of MERS-­CoV infection. Males are more susceptible viral infection outbreaks. to MERS-­CoV and SARS-­CoV-2 infections. Up to half of the patients with coronavirus infection have comorbidities such as Epidemiology and clinical characteristics of human diabetes, hypertension, and cardiovascular disease and older coronavirus infection age has been reported as an important predictor of increased Table 1 presents the epidemiology and clinical characteristics of mortality in coronavirus infection.3–5 Clinical and laboratory three outbreaks of coronavirus infection. Although the mortality features of coronavirus infection by SARS-­CoV, MERS-­CoV, rate of SARS-­CoV-2 infection is the lowest among the three and SARS-­CoV-2 have some similarities among them. Fever, 2 of 8 birpublications.org/bjr Br J Radiol;93:20200515 Imaging Findings of Coronavirus Infections BJR Table 2. Imaging findings of coronavirus infection Characteristics SARS-­CoV MERS-­CoV SARS-­CoV-2 Chest Radiograph Initial imaging    Normal finding % 20 17 31  Parenchymal abnormalities  GGO + +++ +++  Consolidation +++ + ++  Nodule -/+ -/+ -  Cavity - -/+ -  Pleural effusion + ++ -/+  Pneumothorax - + -  Distribution  Transverse Peripheral Peripheral Peripheral  Longitudinal Lower lung Middle & lower lung Lower lung/random  Laterality Unilateral Unilateral Bilateral Follow-­up imaging with progression   Entire bilateral lung Entire bilateral lung Entire bilateral lung Prognostic determinant   CXR score CXR score, pleural effusion, pneumothorax CXR score Chest tomography Initial imaging    Parenchymal abnormalities  GGO +++ +++ ++++  Consolidation ++ ++ ++  Mixed GGO & consolidation ++ ++ ++  Intralobular interstitial thickening ++ + ++  Interlobular septal thickening ++ ++ ++  Crazy paving appearance ++ + +  Reticulation - - -  Traction bronchiectasis - - -  Large nodule - - -  Centrilobular nodule - -/+ -  Cavity - - -  Pleural effusion + ++ -  Pneumothorax - - -  Hilar or mediastinal LN enlargement - - -  Distribution Peripheral, lower lung Peripheral, lower lung Peripheral, random  Laterality Unilateral Unilateral Bilateral Follow-­up imaging after 4 weeks    Predominant findings Signs of fibrosis Signs of fibrosis Signs of fibrosis Prognostic determinant   CT score CT score, pleural effusion CT score SARS-­CoV = severe acute respiratory syndrome coronavirus, MERS-­CoV = Middle East respiratory syndrome coronavirus, SARS-­CoV-2=severe acute respiratory syndrome coronavirus 2, a extent of each parenchymal abnormality <25%, ++;≥25%,<50%, +++;≥50%,<75%, ++++;≥75%, GGO = ground-­glass opacity, CXR = chest radiograph, LN = lymph node 3 of 8 birpublications.org/bjr Br J Radiol;93:20200515 BJR Franquet et al Figure 2. Initial imaging presentation of coronavirus infection. Figure 4. A 31-­year-­old male with SARS-­CoV infection. (a) Ini- (a) Initial chest radiograph (CXR) obtained from a 52-­year-­old tial chest radiograph (CXR) obtained on the day of admission male patient with SARS-­CoV infection shows a focal nodu- shows unilateral lobar consolidation in left lung. (b) Follow-­up lar opacity in the peripheral area of right middle lung zone. CXR obtained 4 days after (a) shows rapid progression with (b) Initial CT scan obtained from a 47-­year-­old female patient bilateral diffuse ground-­glass opacities (GGOs) and consolida- with SARS-­CoV infection shows focal area of ground-­glass tion. (c) Follow-­up chest CT obtained 40 days after admission opacity (GGO) with crazy paving appearance in the periph- shows bilateral diffuse GGOs with superimposed intralobular eral portion of right lower lobe. (c, d) Initial CXR and CT scan interstitial thickenings and reticulation, suggesting pulmonary obtained from a 36-­ year-­ old male patient with MERS-­ CoV fibrosis. infection show multifocal patchy consolidation in left middle to lower lung zones on CXR (c) and focal airspace consolida- tion with air-­bronchogram, ill-­defined nodules, and peripheral GGOs on CT scan (d). (e, f) Initial CXR and CT scan obtained from a 73-­year-­old male patient with SARS-­CoV-2 infection show bilateral multifocal GGOs on CXR (e) and patchy areas of GGO with crazy paving appearance with peripheral pre- dominance on CT scan (f). Imaging findings of coronavirus infection Initial and follow-up chest radiographs (CXR) findings Table 2 summarizes imaging findings of coronavirus infection. Approximately 15%–20% of patients with coronavirus infec- tion have normal initial CXR.6–8 The most common initial CXR findings of coronavirus infection are peripheral focal or multi- focal airspace consolidation, ground-­glass opacities (GGO), or both6–8 (Figures 2–5). However, initial imaging in SARS-­CoV (Figures 2–4) and MERS-­CoV infections (Figures 2 and 5) usually shows unilateral and middle-­to-­lower lung zone involvement of cough, and dyspnea are the major symptoms in those admitted parenchymal lesions, whereas bilateral lung involvements with to the hospital. Gastrointestinal symptoms such as vomiting or lower lung zone or no zonal predominance are more common diarrhea are relatively rare in SARS-­CoV-2 infection, compared in SARS-­ CoV-2 infection6–8 (Figure 2). Cavity and nodular to 20–26% of patients with SARS-­CoV or MERS-­CoV infection opacity are rare in coronavirus infection. Pleural effusion is rare having gastrointestinal symptoms.3,4 In terms of laboratory find- in SARS-­CoV-2 infection, but it occurs approximately 15 and ings, a significant number of patients have lymphocytopenia in 30% of SARS-­CoV and MERS-­CoV infections during first week coronavirus infection, indicating the consumption of immune of infection6,7 (Figure 6). As the disease progresses, parenchymal cells and resultant impairment of cellular immunity.3,4 abnormalities eventually spread to involve the lungs bilaterally in coronavirus infection (Figures 3–7). Initial and follow-up chest CT findings Similar to the CXR findings of coronavirus infection, the CT findings include GGO with or without interlobular septal Figure 3. A 36-­year-­old male patient with SARS-­CoV infec- tion. (a) Initial chest radiograph (CXR) shows focal nodular Figure 5. A 60-­year-­old male patient with MERS-­CoV infec- consolidation in left upper lung zone. (b) Follow-­ up CXR tion. (a) Chest radiograph (CXR) obtained on 8 days after obtained 6 days after (a) shows rapid progression with bilat- exposure shows consolidation and GGOs in right upper lung eral diffuse consolidation and GGOs. zone. (b) Follow-­up CXR obtained 18 days after exposure shows multifocal consolidations in both lungs. (c) Follow-­up chest CT obtained on the same day with (b) shows bilateral, multifocal, mixed consolidation and GGOs with crazy paving appearance, suggesting organizing pneumonia. 4 of 8 birpublications.org/bjr Br J Radiol;93:20200515 Imaging Findings of Coronavirus Infections BJR Figure 6. A 68-­year-­old male with MERS-­CoV infection. (a) Figure 8. A 68-­year-­old male patient with MERS-­CoV infec- Initial chest radiograph (CXR) obtained 1 day after symp- tion. He had a history of visiting Bahrain and suffered from tom onset shows ill-­ defined patchy ground-­ glass opacities fever, myalgia, and dry cough. (a, b) Axial and coronal images (GGOs) in both middle to lower lung zones. (b) Follow-­ up of chest CT scan obtained 4 days after symptom onset show CXR obtained 14 days after symptom onset shows rapid pro- mixed consolidation and ground-­glass opacity with the crazy gression with bilateral diffuse GGOs and consolidation in both paving appearance in right upper lobe. lungs. Also note blunting of left costophrenic angle, suggest- ing pleural effusion. (c) Follow-­up chest CT obtained 18 days after symptom onset shows bilateral consolidation and GGOs with bilateral pleural effusion. He died of respiratory failure. The location and distribution of parenchymal abnormalities and disease progression patterns are similar to those seen on thickening, consolidation, or a combination of both; these are CXRs.9–11,14 During the early stage of the disease, parenchymal the most common findings during the first two weeks of coro- abnormalities are usually located in the peripheral lung; from navirus infection9–11 (Figures 2 and 8–10). In SARS-­CoV infec- there, they eventually spread to involve both lungs when the tion, reticulation is evident after the second week of infection disease progresses (Figure 10). Parenchymal abnormalities and persists in half of the patients after 4 weeks9 (Figure 4). In usually have a peripheral and basilar predilection in MERS-­CoV MERS-­ CoV infection, crazy paving abnormalities and orga- infection10 (Figures 2 and 5), whereas with peripheral or both nizing pneumonia (OP) are seen during the second and third peripheral and central predilection bilateral multilobe lesions weeks of infection10 (Figure 5). In SARS-­CoV-2 infection, GGO are seen in SARS-­CoV-2 infection11,14 (Figures 2, 9–11, 13 and (with or without crazy paving appearance) and consolidation 14). In the chronic stage of coronavirus infection, variable-­sized show a decrease in extents, whereas a mixed pattern of GGO GGO with interlobular septal and intralobular interstitial thick- and consolidation demonstrates an increase after second week of enings are the most common findings. Signs of fibrosis such as infection11 (Figure 11). Cavity, centrilobular nodules (Figure 12), parenchymal bands, reticulation, traction bronchiectasis, irreg- mediastinal, or hilar lymph node enlargement are rarely seen in ular interface signs are also usually seen9–11 (Figures 4, 9, 13 and coronavirus infection. Pulmonary vascular enlargements in areas 15). In SARS-­CoV infection, GGO and interstitial opacity in the of lung opacity can be seen in more than half of the patients with SARS-­CoV-2 infection12 and venous or arterial thromboembolic disease may be complicated in about 30% of critically ill patients Figure 9. A 64-­year-­old male patient with SARS-­CoV-2 infec- with SARS-­CoV-2 infection due to excessive vascular inflamma- tion. (a) Initial chest radiograph (CXR) obtained 7 days after tion or diffuse intravascular coagulation13 (Figures 13 and 14). symptom onset shows bilateral multifocal patchy ground-­ glass opacities (GGOs) with peripheral predominance. (b, c) Chest CT scans obtained on the same day with (a) show Figure 7. A 36-­year-­old male patient with MERS-­CoV infec- multifocal patchy and diffuse GGOs with the crazy paving tion. He had a contact history of MERS patients and suffered appearance and mixed GGO and consolidation in both lungs. from fever. (a) Initial chest radiograph (CXR) shows multifocal (d) Follow-­up CXR after 2 days of (a) shows rapid progres- patchy consolidation in left middle to lower lung zones. (b) sion with bilateral diffuse consolidations and GGOs. (e, f) Fol- Follow-­up CXR obtained 15 days after (a) shows increased low-­up chest CT scans obtained 1 month later show markedly extents of multifocal patchy consolidation in left middle to decreased extent of GGO with remnant subpleural line and lower lung zones and new appearance of diffuse ground-­glass traction bronchiectasis, suggesting pulmonary fibrosis. opacities and consolidation in the peripheral portion of right lung. (c) Follow-­ up CXR obtained 18 days after (a) shows bilateral diffuse consolidation, suggesting acute respiratory distress syndrome. 5 of 8 birpublications.org/bjr Br J Radiol;93:20200515 BJR Franquet et al Figure 10. A 78-­year-­old male patient with SARS-­CoV-2 infec- Figure 12. A 43-­year-­old male with SARS-­CoV infection. Chest tion. He had a history of exposure to an infected patient and CT obtained 25 days after symptom onset shows bilateral dif- had fever and myalgia for 1 day. (a, b) Initial chest CT scans fuse ill-­defined centrilobular and ground-­glass opacity nod- obtained 2 days after symptom onset show focal subpleu- ules in both lungs. Also, note focal consolidation in right lower ral ground-­glass opacity (GGO) in left lower lobe. (c, d) Fol- lobe. low-­up CT scans obtained 7 days after symptom onset show increased extent of GGO in left lower lobe and new appear- ance of multifocal subpleural patchy GGOs with the crazy paving appearance in both lungs. (e) Follow-­up chest radio- graph obtained 15 days after symptom onset shows bilateral diffuse GGOs and consolidation in both lungs, suggesting dif- fuse alveolar damage. He died of respiratory failure. Differential diagnosis convalescent phase usually resolve over time but air trapping Coronavirus infection is sometimes difficult to distinguish from may persist.15 other viral infections, bacterial pneumonia, or OP associated with other causes. Viral pneumonia in an immunocompetent patient Prognostic determinants can be divided into bronchopneumonia, OP, and diffuse alveolar Several studies have been conducted to investigate the correla- damage (DAD) pattern. OP and DAD pattern are common features tion between imaging findings and clinical outcomes. Higher of coronavirus pneumonia and can be seen during the disease CT and CXR scores (percentage of lungs or the number of zones course or in advanced disease. Viral pneumonia showing OP or involved with opacification), especially in patients with old age and comorbid lung illness, could be used as fatal prognostic indicators Figure 13. A 78-­ year-­old female patient with SARS-­ CoV-2 in SARS-­CoV infection.5 In MERS-­CoV infection, a greater extent infection. (a) Initial chest radiograph shows bilateral dif- of parenchymal abnormalities, pleural effusion, and pneumothorax fuse consolidation in both lungs. (b) Lung window image of was associated with poor prognosis and short-­ term mortality contrast-­enhanced chest CT scan obtained on the same day (Figure 6).10,16 Although imaging features that help determine the with (a) shows mixed ground-­glass opacities (GGOs) and con- prognosis of SARS-­CoV-2 infection are not yet fully understood, solidation in both lungs. (c, d) Mediastinal window images of older age and progressive consolidation with a greater extent on contrast-­enhanced chest CT scan obtained on the same day imaging might suggest poorer prognosis (Figure 10). with (a) show thromboembolism (arrow) involving right inter- lobar pulmonary artery and irregular-­walled vessels (arrow- head) toward consolidation in right lower lobe. (e) Follow-­up Figure 11. A 64-­ year-­old female patient with SARS-­ CoV-2 chest CT scan after 1 month of (a) shows decreased extent infection. (a) Initial chest radiograph shows faint ground-­glass of mixed GGOs and consolidation with remnant multifocal opacities (GGOs) in both lower lung zones. (b, c) Follow-­up patchy GGOs, parenchymal bands, traction bronchiectasis, CT scans obtained 14 days after symptom onset show mixed and irregular interface, suggesting pulmonary fibrosis. GGOs and consolidation in both lower lung lobes. 6 of 8 birpublications.org/bjr Br J Radiol;93:20200515 Imaging Findings of Coronavirus Infections BJR Figure 14. A 71-­year-­old male patient with SARS-­CoV-2 infec- imaging findings of OP. Therefore, cryptogenic OP and OP associ- tion. (a) Initial chest radiograph shows bilateral peripheral ated with infection, drug, and collagen vascular disease should be ground-­ glass opacities (GGOs) and multifocal patchy con- considered to be differentiated from coronavirus infection. solidation in both lungs. (b) Lung window image of contrast-­ enhanced chest CT scan obtained on the same day with (a) It is difficult to differentiate coronavirus infection from other shows consolidation and patchy GGOs in the subpleural areas diseases by imaging alone; therefore, clinical manifestation, of both lower lobes. (c) Mediastinal window image of contrast-­ contact history, and laboratory tests should also be considered to enhanced chest CT scan obtained on the same day with (a) make the final diagnosis. shows thromboembolism (arrow) involving right lower lobar pulmonary artery. Role of imaging in coronavirus infection The main role of imaging in viral infection outbreak is to identify the presence of pneumonia, provide differential diagnosis, and monitor changes of pneumonia with treatment. When deciding which imaging modality to use for establishing a diagnosis or for guiding management in viral infection outbreak, there are several factors to consider; patient’s clinical severity, radiation hazard to the patient, accessibility of imaging modalities, possibility of virus transmission to uninfected healthcare workers and other patients, and community infection status.17 Although it is insensitive in mild or early coronavirus infec- tion, CXR remains the first-­line and the most commonly used imaging modality because it is rapid and easily accessible. It is also helpful for monitoring patient progress during treatment. DAD patterns include influenza virus, Hantavirus, adenovirus, CT is more sensitive to detect early parenchymal lung abnor- and varicella-­zoster virus pneumonia. Consolidation and GGO malities and disease progression, and can provide an alterna- with subpleural or peribronchovascular predominance are typical tive diagnosis. However, CT lacks equipment portability with imaging performed within an infected patient’s isolation room and has a risk of virus transmission along the transport route to a CT scanner and within the CT room. CT can be used when Figure 15. A 32-­year-­old male with MERS-­CoV infection. (a) the patient has symptoms but the CXR is normal or there are Chest radiograph (CXR) obtained on 15 days after symptom only questionable abnormalities on CXR. CT is also indicated onset shows consolidation and ground-­glass opacities in both in patients with functional impairment and/or hypoxemia after middle to lower lung zones. (b) Follow-­up CXR obtained 50 recovery from coronavirus infection. Contrast-­ enhanced CT days after symptom onset shows linear and patchy opaci- may be indicated in patients with signs of thrombotic compli- ties in both lower lung zones, which may represent fibrosing cation. The appropriate use of imaging in each clinical situation sequelae. (c, d) Follow-­up chest CT scans obtained on the same day with (b) show parenchymal bands, linear opacities, should be considered on this basis.17 and traction bronchiectasis in both lower lobes, suggesting remnant fibrosis. Conclusions Although imaging findings of coronavirus infection are non-­ specific and have significant overlap among those of SARS-­CoV, MERS-­ CoV, and SARS-­ CoV-2 infections, they have several important differences. The most common initial CXR and CT findings are GGO and consolidation with peripheral predomi- nance and these lesions eventually spread to involve both lungs as the disease progresses and pulmonary fibrosis may develop after long-­term follow-­up. Imaging features that help determine the clinical outcome or prognosis of coronavirus infection are the extents of parenchymal abnormalities. The greater extents of parenchymal abnormalities, especially in patients with old age or comorbidity, might suggest poorer prognosis in corona- virus infection, necessitating intensive care unit management, or predicting oncoming succumbing to death. Acknowledgment We gratefully acknowledge Miri Jeong for providing graphic illustration. 7 of 8 birpublications.org/bjr Br J Radiol;93:20200515 BJR Franquet et al REFERENCES 1. Li X, Geng M, Peng Y, Meng L, Lu S. of Roentgenology 2004; 182: 1119–22. doi: W1Available from. doi: https://​doi.​org/​10.​ Molecular immune pathogenesis and https://​doi.​org/​10.​2214/​ajr.​182.​5.​1821119 2214/​AJR.​20.​23443 diagnosis of COVID-19. J Pharm Anal 2020; 7. Das KM, Lee EY, Jawder SEA, Enani MA, 13. Klok FA, Kruip MJHA, van der Meer NJM, 10: 102–8. doi: https://​doi.​org/​10.​1016/​j.​jpha.​ Singh R, Skakni L, et al. Acute middle Arbous MS, Gommers DAMPJ, Kant KM, 2020.​03.​001 East respiratory syndrome coronavirus: et al. Incidence of thrombotic complications 2. Koo HJ, Lim S, Choe J, Choi S-­H, Sung H, temporal lung changes observed on the chest in critically ill ICU patients with COVID-19. Do K-­H, . Radiographic and CT features radiographs of 55 patients. American Journal Thromb Res 2020; 191: 145–7. doi: https://​ of viral pneumonia. RadioGraphics 2018; of Roentgenology 2015; 205: W267–74. doi: doi.​org/​10.​1016/​j.​thromres.​2020.​04.​013 38: 719–39. doi: https://​doi.​org/​10.​1148/​rg.​ https://​doi.​org/​10.​2214/​AJR.​15.​14445 14. Chung M, Bernheim A, Mei X, Zhang N, 2018170048 8. Wong HYF, HYS L, Fong AH, Leung ST, Huang M, Zeng X, et al. Ct imaging features 3. Wu C, Chen X, Cai Y, Xia Jia’an, Zhou X, Xu Chin TW LCSY, et al. Frequency and of 2019 novel coronavirus (2019-­nCoV. S, et al. Risk factors associated with acute distribution of chest radiographic findings Radiology 2020; 295: 202–7. doi: https://​doi.​ respiratory distress syndrome and death in COVID-19 positive patients. Radiology org/​10.​1148/​radiol.​2020200230 in patients with coronavirus disease 2019 2020;Available from. 15. Chang Y-­C, Yu C-­J, Chang S-­C, Galvin pneumonia in Wuhan, China. JAMA Intern 9. Ooi GC, Khong PL, Müller NL, Yiu WC, JR, Liu H-­M, Hsiao C-­H, et al. Pulmonary Med 2020;Available from. doi: https://​doi.​ Zhou LJ, Ho JCM, , et al. Severe acute sequelae in convalescent patients after severe org/​10.​1001/​jamainternmed.​2020.​0994 respiratory syndrome: temporal lung changes acute respiratory syndrome: evaluation 4. Assiri A, Al-­Tawfiq JA, Al-­Rabeeah AA, at thin-­section CT in 30 patients. Radiology with thin-­section CT. Radiology 2005; 236: Al-­Rabiah FA, Al-­Hajjar S, Al-­Barrak A, 2004; 230: 836–44. doi: https://​doi.​org/​10.​ 1067–75. doi: https://​doi.​org/​10.​1148/​radiol.​ et al. Epidemiological, demographic, and 1148/​radiol.​2303030853 2363040958 clinical characteristics of 47 cases of middle 10. Das KM, Lee EY, Enani MA, AlJawder SE, 16. Cha MJ, Chung MJ, Kim K, Lee KS, Kim TJ, East respiratory syndrome coronavirus Singh R, Bashir S, et al. Ct correlation with Kim TS. Clinical implication of radiographic disease from Saudi Arabia: a descriptive outcomes in 15 patients with acute middle scores in acute middle East respiratory study. Lancet Infect Dis 2013; 13: 752–61. East respiratory syndrome coronavirus. syndrome coronavirus pneumonia: report doi: https://​doi.​org/​10.​1016/​S1473-​3099(​13)​ American Journal of Roentgenology 2015; from a single tertiary-­referral center of 70204-4 204: 736–42. doi: https://​doi.​org/​10.​2214/​ South Korea. Eur J Radiol 2018; 107: 5. SF K, Lee TY, Huang CC, Cheng YF, SH AJR.​14.​13671 196–202. doi: https://​doi.​org/​10.​1016/​j.​ejrad.​ N, Kuo YL, et al. Severe acute respiratory 11. Wang Y, Dong C, Hu Y, Li C, Ren Q, Zhang 2018.​09.​008 syndrome: prognostic implications of X, et al. Temporal changes of CT findings 17. Rubin GD, Ryerson CJ, Haramati LB, chest radiographic findings in 52 patients. in 90 patients with COVID-19 pneumonia: Sverzellati N, Kanne JP, Raoof S, et al. The Radiology 2004; 233: 173–81. a longitudinal study. Radiology 2020;: role of chest imaging in patient management 6. Hsieh S-­C, Chan WP, Chien JC-­W, Lee W-­S, 200843Available from. doi: https://​doi.​org/​ during the COVID-19 pandemic: a Yao M-­S, Choi W-­M, et al. Radiographic 10.​1148/​radiol.​2020200843 multinational consensus statement from appearance and clinical outcome 12. Parry AH, Wani AH. Segmental pulmonary the Fleischner Society. Radiology 2020; 296: correlates in 26 patients with severe acute vascular changes in COVID-19 pneumonia. 172–180Available from. doi: https://​doi.​org/​ respiratory syndrome. American Journal American Journal of Roentgenology 2020;: 10.​1148/​radiol.​2020201365 8 of 8 birpublications.org/bjr Br J Radiol;93:20200515