Pulmonary imaging of pandemic influenza H1N1 infection: relationship between clinical presentation and disease burden on chest radiography and CT

Viral Pneumonias

Viral pneumonia is usually community acquired and caused by influenza, parainfluenza, respiratory syncytial virus, human metapneumovirus, and adenovirus. Many of these infections are airway centric and chest imaging demonstrates bronchiolitis and bronchopneumonia, With the exception of adenovirus infections, the presence of lobar consolidation usually suggests bacterial coinfection. Community-acquired viral pathogens can cause more severe pneumonia in immunocompromised hosts, who are also susceptible to CMV and varicella infection. These latter 2 pathogens are less likely to manifest the striking airway-centric pattern. Airway-centric pattern is distinctly uncommon in Hantavirus pulmonary syndrome, a rare environmentally acquired infection with high mortality.

Community-Acquired Pneumonia: Postpandemic, Not Post-COVID-19

The coronavirus disease 2019 (COVID-19) pandemic upended our approach to imaging community-acquired pneumonia, and this will alter our diagnostic algorithms for years to come. In light of these changes, it is worthwhile to consider several postpandemic scenarios of community-acquired pneumonia: (1) patient with pneumonia and recent positive COVID-19 testing; (2) patient with air space opacities and history of prior COVID-19 pneumonia (weeks earlier); (3) multifocal pneumonia with negative or unknown COVID-19 status; and (4) lobar or sublobar pneumonia with negative or unknown COVID-19 status. In the setting of positive COVID-19 testing and typical radiologic findings, the diagnosis of COVID-19 pneumonia is generally secure. The diagnosis prompts vigilance for thromboembolic disease acutely and, in severely ill patients, for invasive fungal disease. Persistent or recurrent air space opacities following COVID-19 infection may more often represent organizing pneumonia than secondary infection. When COVID-19 status is unknown or negative, widespread airway-centric disease suggests infection with mycoplasma, Haemophilus influenzae, or several respiratory viruses. Necrotizing pneumonia favors infection with pneumococcus, Staphylococcus, Klebsiella, and anaerobes. Lobar or sublobar pneumonia will continue to suggest the diagnosis of pneumococcus or consideration of other pathogens in the setting of local outbreaks. A positive COVID-19 test accompanied by these imaging patterns may suggest coinfection with one of the above pathogens, or when the prevalence of COVID-19 is very low, a false positive COVID-19 test. Clinicians may still proceed with testing for COVID-19 when radiologic patterns are atypical for COVID-19, dependent on the patient's exposure history and the local epidemiology of the virus.

CHEST CT USAGE IN COVID-19 PNEUMONIA: MULTICENTER STUDY ON RADIATION DOSES AND DIAGNOSTIC QUALITY IN BRAZIL

We assessed variations in chest CT usage, radiation dose and image quality in COVID-19 pneumonia. Our study included all chest CT exams performed in 533 patients from 6 healthcare sites from Brazil. We recorded patients' age, gender and body weight and the information number of CT exams per patient, scan parameters and radiation doses (volume CT dose index-CTDIvol and dose length product-DLP). Six radiologists assessed all chest CT exams for the type of pulmonary findings and classified CT appearance of COVID-19 pneumonia as typical, indeterminate, atypical or negative. In addition, each CT was assessed for diagnostic quality (optimal or suboptimal) and presence of artefacts. Artefacts were frequent (367/841), often related to respiratory motion (344/367 chest CT exams with artefacts) and resulted in suboptimal evaluation in mid-to-lower lungs (176/344) or the entire lung (31/344). There were substantial differences in CT usage, patient weight, CTDIvol and DLP across the participating sites.

Clinical Characteristics and CT Findings in 148 Non-COVID-19 Influenza-Like Illness Cases: A Retrospective Control Study

Background: This study was to collect clinical features and computed tomography (CT) findings of Influenza-Like Illness (ILI) cases, and to evaluate the correlation between clinical data and the abnormal chest CT in patients with the Influenza-Like Illness symptoms. Methods: Patients with the Influenza-Like Illness symptoms who attended the emergency department of The Six Medical Center of The PLA General Hospital from February 10 to April 1, 2020 were enrolled. Clinical and imaging data of the enrolled patients were collected and analyzed. The association between clinical characteristics and abnormal chest CT was also analyzed. Results: A total of 148 cases were enrolled in this study. Abnormalities on chest CT were detected in 61/148 (41.2%) patients. The most common abnormal CT features were as follows: patchy consolidation 22/61(36.1%), ground-glass opacities 21/61(34.4%), multifocal consolidations 17/61(27.9%). The advanced age and underlying diseases were significantly associated with abnormal chest CT. Conclusions: Abnormal chest CT is a common condition in Influenza-Like Illness cases. The presence of advanced age and concurrent underlying diseases is significantly associated with abnormal chest CT findings in patients with ILI symptoms. The chest CT characteristic of ILI is different from the manifestation of COVID-19 infection, which is helpful for differential diagnosis.

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

Influenza viruses were responsible for most adult viral pneumonia. Presently, coronavirus disease 2019 (COVID-19) has evolved into serious global pandemic. COVID-19 outbreak is expected to persist in months to come that will be synchronous with the influenza season. The management, prognosis, and protection for these two viral pneumonias differ considerably and differentiating between them has a high impact on the patient outcome. Reverse transcriptase polymerase chain reaction is highly specific but has suboptimal sensitivity. Chest computed tomography (CT) has a high sensitivity for detection of pulmonary disease manifestations and can play a key-role in diagnosing COVID-19. We reviewed 47 studies and delineated CT findings of COVID-19 and influenza pneumonia. The differences observed in the chest CT scan can be helpful in differentiation. For instance, ground glass opacities (GGOs), as the most frequent imaging finding in both diseases, can differ in the pattern of distribution. Peripheral and posterior distribution, multilobular distribution, pure or clear margin GGOs were more commonly reported in COVID-19, whereas central or peri-bronchovascular GGOs and pure consolidations were more seen in influenza A (H1N1). In review of other imaging findings, further differences were noticed. Subpleural curvilinear lines, sugar melted sign, intra-lesional vascular enlargement, reverse halo sign, and fibrotic bands were more reported in COVID-19 than H1N1, while air space nodule, tree-in-bud, bronchiectasia, pleural effusion, and cavitation were more seen in H1N1. This delineation, when combined with clinical manifestations and laboratory results may help to differentiate these two viral infections.

Point-of-care Lung Ultrasound Is More Sensitive than Chest Radiograph for Evaluation of COVID-19

INTRODUCTION

Current recommendations for diagnostic imaging for moderately to severely ill patients with suspected coronavirus disease 2019 (COVID-19) include chest radiograph (CXR). Our primary objective was to determine whether lung ultrasound (LUS) B-lines, when excluding patients with alternative etiologies for B-lines, are more sensitive for the associated diagnosis of COVID-19 than CXR.

METHODS

This was a retrospective cohort study of all patients who presented to a single, academic emergency department in the United States between March 20 and April 6, 2020, and received LUS, CXR, and viral testing for COVID-19 as part of their diagnostic evaluation. The primary objective was to estimate the test characteristics of both LUS B-lines and CXR for the associated diagnosis of COVID-19. Our secondary objective was to evaluate the proportion of patients with COVID-19 that have secondary LUS findings of pleural abnormalities and subpleural consolidations.

RESULTS

We identified 43 patients who underwent both LUS and CXR and were tested for COVID-19. Of these, 27/43 (63%) tested positive. LUS was more sensitive (88.9%, 95% confidence interval (CI), 71.1-97.0) for the associated diagnosis of COVID-19 than CXR (51.9%, 95% CI, 34.0-69.3; p = 0.013). LUS and CXR specificity were 56.3% (95% CI, 33.2-76.9) and 75.0% (95% CI, 50.0-90.3), respectively (p = 0.453). Secondary LUS findings of patients with COVID-19 demonstrated 21/27 (77.8%) had pleural abnormalities and 10/27 (37%) had subpleural consolidations.

CONCLUSION

Among patients who underwent LUS and CXR, LUS was found to have a higher sensitivity than CXR for the evaluation of COVID-19. This data could have important implications as an aid in the diagnostic evaluation of COVID-19, particularly where viral testing is not available or restricted. If generalizable, future directions would include defining how to incorporate LUS into clinical management and its role in screening lower-risk populations.

Influenza A virus H1N1 associated pneumonia - acute and late aspects evaluated with high resolution tomography in hospitalized patients

Background

Influenza A (H1N1) virus often compromises the respiratory tract, leading to pneumonia, which is the principal cause of death in these patients. The purpose of this study was to review the acute and late phase pulmonary findings in influenza A(H1N1) associated pneumonia using high resolution computed tomography (HRCT), and to determine the importance of performing end expiration series.

Methods

Between July and August 2009, 140 patients presented with influenza A (H1N1) confirmed by real-timepolymerase chain reaction. Out of these, 27 patients underwent HRCT in the acute and late phases of pneumonia, allowing for a comparative study. Late phase exams were performed due to clinical worsening and up to 120 days later in patients with persistent complaints of dyspnea.

Results

Ground glass opacities, consolidations, and the combination of both were associated with the acute phase, whereas persistence or worsening of the lesions, lesion improvement, and air trapping in the end expiration series (as seen using HRCT, n=6) were observed in the late phase.

Conclusions

In the HRCT end expiration series, air trapping was found in the late phase of H1N1 associated pneumonia. Generally, these exams are not evaluated in research articles, and air trapping has not previously been studied using the end expiration series. Our study brings more scientific knowledge about aspects of pulmonary involvement by influenza A (H1N1), through evaluation with end expiration series, which makes the CT exam dynamic, translating the respiratory movement, and showing bronchial alteration.

Safety and efficacy of monoclonal antibody VIS410 in adults with uncomplicated influenza A infection: Results from a randomized, double-blind, phase-2, placebo-controlled study

BACKGROUND

VIS410, a broadly neutralizing monoclonal antibody that binds the hemagglutinin stem of influenza A viruses, was safe and efficacious in a human H1N1 virus challenge study. This study evaluated the safety and tolerability of VIS410 in non-hospitalized adult patients with uncomplicated influenza A.

METHODS

Patients 18 to 65 years of age with symptom onset within 72 h were randomized 1:1:1 to receive a single intravenous infusion of VIS410 4000 mg, 2000 mg, or placebo. Neuraminidase inhibitor therapy was prohibited. Treatment-emergent adverse events (TEAEs) were evaluated up to 100 days post-infusion. Influenza symptoms were assessed daily for 10 days using the FLU-PRO tool. Nasopharyngeal virus shedding was assessed by quantitative reverse-transcription PCR (qRT-PCR) and viral culture through Day 7.

FINDINGS

Of the 150 patients randomized, 148 received study drug, and 138 were confirmed influenza A positive. Median age was 42 years; median time from symptom onset to treatment was 42 h; 93% had influenza A subtype H3N2.

SAFETY

TEAEs, most commonly diarrhea of mild severity, were dose-related, occurring in 55%, 35%, and 24% of the 4000 mg, 2000 mg, and placebo patients, respectively. Two serious adverse events occurred, both in placebo patients.

SYMPTOM ANALYSES

Baseline FLU-PRO symptom scores were balanced among groups. Mean scores were lower by Days 3 and 4 in the pooled VIS410 treatment group versus placebo (p < 0.023), with a tendency toward faster resolution by Kaplan-Meier analysis.

VIROLOGY ANALYSES

VIS410 was associated with reduced median nasopharyngeal viral load TCID₅₀ AUC_Day7 (days × log₁₀ TCID₅₀/mL) (3.66 pooled VIS410 vs 4.78 placebo, p = 0.08) and in the subset of patients with baseline hemagglutination inhibition (HAI) titer ≤40 (overall, 74% of patients) was significantly reduced vs placebo (4.218 pooled VIS410 vs 6.152 placebo, p = 0.009). Kaplan-Meier estimated time to resolution of viral shedding was reduced (1.9 vs 3.6 days, p = 0.03) in VIS410 treated patients. There was a trend toward greater proportion of culture-negative patients by Day 3 (66.7% vs 51.1%, p = 0.11); when this analysis was limited to the subset of patients with positive baseline cultures, this difference became more pronounced (63.2% vs 42.5%, p = 0.053). No differences were observed in nasopharyngeal influenza qRT-PCR profiles, which represent both live and neutralized virus.

INTERPRETATION

VIS410 was safe and well tolerated in adults with uncomplicated influenza A, with favorable effects on symptom resolution and virus replication.

TRIAL REGISTRATION

Clinical Trials: NCT02989194.

FUNDING

This project was funded in part with Federal funds from the Department of Health and Human Services; Office of the Assistant Secretary for Preparedness and Response; Biomedical Advanced Research and Development Authority (BARDA), under Contract No. HHSO100201500018C.

Community acquired respiratory virus infections in cancer patients-Guideline on diagnosis and management by the Infectious Diseases Working Party of the German Society for haematology and Medical Oncology

BACKGROUND

Community acquired viruses (CRVs) may cause severe disease in cancer patients. Thus, efforts should be made to diagnose CRV rapidly and manage CRV infections accordingly.

METHODS

A panel of 18 clinicians from the Infectious Diseases Working Party of the German Society for Haematology and Medical Oncology have convened to assess the available literature and provide recommendations on the management of CRV infections including influenza, respiratory syncytial virus, parainfluenza virus, human metapneumovirus and adenovirus.

RESULTS

CRV infections in cancer patients may lead to pneumonia in approximately 30% of the cases, with an associated mortality of around 25%. For diagnosis of a CRV infection, combined nasal/throat swabs or washes/aspirates give the best results and nucleic acid amplification based-techniques (NAT) should be used to detect the pathogen. Hand hygiene, contact isolation and face masks have been shown to be of benefit as general infection management. Causal treatment can be given for influenza, using a neuraminidase inhibitor, and respiratory syncytial virus, using ribavirin in addition to intravenous immunoglobulins. Ribavirin has also been used to treat parainfluenza virus and human metapneumovirus, but data are inconclusive in this setting. Cidofovir is used to treat adenovirus pneumonitis.

CONCLUSIONS

CRV infections may pose a vital threat to patients with underlying malignancy. This guideline provides information on diagnosis and treatment to improve the outcome.

Influenza A (H1N1)

In March 2009, an outbreak of human infected swine influenza, first name by WHO, occurred in Mexico that rapidly spread worldwide. On Apr 30, 2009, the WHO, the United Nations Food and Agriculture Organization and the World Organization for Animal Health agreed to use the name of influenza A (H1N1), which was then used in bulletins issued by Ministry of Health in China.

The CT appearance of lower respiratory infection due to parainfluenza virus in adults

OBJECTIVE

We retrospectively reviewed the CT findings of lower respiratory tract infection (LRTI) due to parainfluenza virus (PIV) to determine the imaging features of PIV infection and to identify any differences compared with the CT appearances of LRTIs due to respiratory syncytial virus (RSV), adenovirus, and influenza virus.

MATERIALS AND METHODS

The imaging features of LRTI from PIV over a 51-month period were retrospectively reviewed. The specific CT findings and overall pattern of infection in patients with LRTI due to PIV were recorded and were then compared with the CT appearances of RSV, adenovirus, and influenza LRTIs using data from a previous study.

RESULTS

Twenty-four chest CT examinations of 24 patients with PIV infection were analyzed. Tree-in-bud opacities were the most common finding (13/24, 54%), and the airway-centric pattern of disease--characterized by combinations of bronchial wall thickening, tree-in-bud opacities, and peribronchiolar consolidation (bronchitis, bronchiolitis, and bronchopneumonia)--was the most common pattern (16/24, 67%). In comparison with previous data on RSV, adenovirus, and influenza virus, PIV showed tree-in-bud opacities and airway-centric patterns significantly more often than adenovirus or influenza virus. PIV and RSV showed similar CT findings and patterns of disease.

CONCLUSION

Despite varying CT appearances of PIV LRTI, it most often shows airway-centric disease and is similar to the appearance of RSV infection, both of which are members of the Paramyxoviridae family of viruses.

Influenza A(H1N1)pdm09-related pneumonia and other complications

Influenza A(H1N1)pdm09 virus infection was associated with significant morbidity, mainly among children and young adults. The majority of patients had self-limited mild-to-moderate uncomplicated disease. However, some patients developed severe illness and some died. In addition to respiratory complications, several complications due to direct and indirect effects on other body systems were associated with influenza A(H1N1)pdm09 virus infection. The main complications reported in hospitalized adults with influenza A(H1N1)pdm09 were pneumonia (primary influenza pneumonia and concomitant/secondary bacterial pneumonia), exacerbations of chronic pulmonary diseases (mainly chronic obstructive pulmonary disease and asthma), the need for intensive unit care admission (including mechanical ventilation, acute respiratory distress syndrome and septic shock), nosocomial infections and acute cardiac events. In experimentally infected animals, the level of pulmonary replication of the influenza A(H1N1)pdm09 virus was higher than that of seasonal influenza viruses. Pathological studies in autopsy specimens indicated that the influenza A(H1N1)pdm09 virus mainly targeted the lower respiratory tract, resulting in diffuse alveolar damage (edema, hyaline membranes, inflammation, and fibrosis), manifested clinically by severe acute respiratory distress syndrome with refractory hypoxemia. Influenza A(H1N1)pdm09-related pneumonia and other complications were associated with increased morbidity and mortality among hospitalized patients.

The value of radiographic findings for the progression of pandemic 2009 influenza A/H1N1 virus infection

Background

Most illnesses caused by pandemic influenza A (H1N1) pdm09 virus (A/H1N1) infection are acute and self-limiting among children. However, in some children, disease progression is rapid and may require hospitalization and transfer to a pediatric intensive care unit (PICU). We investigated factors associated with rapid disease progression among children admitted to hospital for A/H1N1 infection, particularly findings on initial chest radiographs.

Methods

In this retrospective study, we investigated the records of children who had received a laboratory or clinical diagnosis of A/H1N1 infection and were admitted to the largest children’s hospital in Japan between May 2009 and March 2010. The medical records were reviewed for age, underlying diseases, vital signs on admission, initial chest radiographic findings, and clinical outcomes. According to chest radiographic findings, patients were classified into 4 groups, as follows: [1] normal (n = 46), [2] hilar and/or peribronchial markings alone (n = 64), [3] consolidation (n = 64), and [4] other findings (n = 29). Factors associated with clinical outcomes were analyzed using logistic regression.

Results

Two hundreds and three patients (median 6.8 years) were enrolled in this study. Fifteen percent (31/203) of patients were admitted to PICU. Among 31 patients, 39% (12/31) of patients required mechanical ventilation (MV). When the initial chest radiographic findings were compared between patients with consolidation (n = 64) and those without consolidation (n = 139), a higher percentage of patients with consolidation were admitted to PICU (29.7% vs.8.6%, P < 0.001) and required MV (17.2% vs. 0.7%, P < 0.001). These findings remain significant when the data were analyzed with the logistic regression (P < 0.001, P < 0.001, respectively).

Conclusions

Consolidation on initial chest radiographs was the most significant factor to predict clinical course of hospitalized children with the 2009 A/H1N1 infection.

2009 pandemic influenza A (H1N1): clinical and laboratory characteristics in pediatric and adult patients and in patients with pulmonary involvement

BACKGROUND

To better understand clinical and laboratory characteristics in children, adults, and patients with lung involvement suffering 2009 pandemic influenza A (H1N1).

METHODS

A total of 442 patients with 2009 pandemic influenza A (H1N1) were retrospectively analyzed.

RESULTS

Comparing to their adult counterpart (n=55), pediatric patients (n=387) had significantly higher frequencies of fever, rhinorrhea, cough, sore throat, nausea/vomiting, and longer length of fever; lower frequencies of chest pain and dyspnea; higher incidence of lymphopenia; and lower incidence of elevated serum C-reactive protein. Among the 227 patients with radiographs available, lung involvement was found in 19 (8.4%) (52.6% consolidation and 47.4% interstitial infiltrations), including 18 children and one adult. One child with lung consolidation died of multiorgan failure. Significant findings in patients with lung involvement included predominant young age (≤ 10 years), prolonged fever, and delayed oseltamivir therapy (≥ 48 hours after onset of illness); higher frequencies of dyspnea, nausea/vomiting, and altered consciousness; and higher incidences of leukopenia, elevated serum creative kinase, and lactic dehydrogenase.

CONCLUSIONS

Among patients with 2009 pandemic influenza A (H1N1), we found significant difference in clinical manifestations between children and adults, and significant differences in clinical and laboratory manifestations between patients with lung involvement and those without. On the basis of data from this study and the existing literature, early treatment with oseltamivir is recommended for patients with 2009 pandemic influenza A (H1N1), regardless of age.

Computed tomography findings of influenza A (H1N1) pneumonia in adults: pattern analysis and prognostic comparisons

AIM

The aim of this study was to evaluate retrospectively the chest computed tomography findings of influenza A (H1N1) pneumonia and their relationship with clinical outcome.

METHODS

Chest computed tomography findings and clinical outcomes of 76 patients with influenza A (H1N1) pneumonia were assessed. Computed tomography findings were evaluated for the presence and distribution of parenchymal abnormalities, which were then classified into 3 patterns: bronchopneumonia, cryptogenic organizing pneumonia (COP), and acute interstitial pneumonia (AIP) patterns. Clinical courses were divided into 2 groups on the basis of necessitating admission to intensive care unit or mechanical ventilation therapy (group 1) or not (group 2).

RESULTS

Lung abnormalities consisted of ground-glass opacity (93%, 71 patients), consolidation (66%, 50 patients), small nodules (61%, 46 patients), and tree-in-bud sign (22%, 17 patients). Lesions were classified into bronchopneumonia (49%, 37 patients), COP (30%, 23 patients), AIP (18%, 14 patients), and unclassifiable (3%, 2 patients) patterns. Patients with AIP pattern had a tendency to belonging to group 1, accounting for 40% (8 of 20 patients) of group 1 course and only 11% (6 of 56 patients) of group 2 course (P = 0.004).

CONCLUSIONS

Computed tomography findings of influenza A (H1N1) pneumonia in adults can be classified into COP, AIP, and bronchopneumonia patterns. Patients presenting with AIP pattern have a tendency to show poor prognosis.

Pulmonary manifestation of novel swine-origin influenza A (H1N1) virus (S-OIV) infection in immunocompromised patients: initial findings with multidetector computed tomography

OBJECTIVE

To describe initial multidetector computed tomographic (MDCT) findings of novel swine-origin influenza A (H1N1) virus (S-OIV) infection in immunocompromised patients and to evaluate whether or not identification of certain abnormalities can help predict patients who are at risk for a severe clinical course.

SUBJECTS AND METHODS

This retrospective study included 13 patients with confirmed S-OIV infection suffering from an underlying immunodeficiency or who were receiving immunosuppressive therapy. All patients underwent MDCT of the thorax due to respiratory distress. All data were read by two independent radiologists who described the type and pattern of opacities, distribution and extent of the abnormalities observed. Adverse outcome measures were defined as acute respiratory distress syndrome with the need for mechanical ventilation, extracorporeal membrane oxygenation or death.

RESULTS

MDCT revealed pulmonary manifestations in 12 (92%) of 13 individuals. Six (50%) patients showed an adverse outcome with development of acute respiratory distress syndrome, 4 of these died. The most common findings were ground-glass opacities (10/12; 83%) and pulmonary consolidation (7/12; 58%) predominantly with a bilateral distribution. Reticular pattern and a tree-in-bud appearance were found in 3/12 (25%), respectively. Bilateral opacities with extensive involvement of the lung parenchyma were most predictive of a severe clinical course.

CONCLUSION

The MDCT scan in immunocompromised patients with confirmed S-OIV infection frequently revealed pulmonary abnormalities, which included ground-glass opacities and consolidations. Therefore, prediction of an adverse clinical outcome could be made in patients with MDCT findings demonstrating bilateral extensive consolidations, often combined with ground-glass opacities.

Chest computed tomography findings in severe influenza pneumonia occurring in neutropenic cancer patients

OBJECTIVE

To describe the chest computed tomography findings for severe influenza H1N1 infection in a series of hospitalized neutropenic cancer patients.

METHODS

We performed a retrospective systematic analysis of chest computed tomography scans for eight hospitalized patients with fever, neutropenia, and confirmed diagnoses of influenza H1N1. The clinical data had been prospectively collected.

RESULTS

Six of eight patients (75%) developed respiratory failure and required intensive care. Prolonged H1N1 shedding was observed in the three mechanically ventilated patients, and overall hospital mortality in our series was 25%. The most frequent computed tomography findings were ground-glass opacity (all patients), consolidation (7/8 cases), and airspace nodules (6/8 cases) that were frequently moderate or severe. Other parenchymal findings were not common. Five patients had features of pneumonia, two had computed tomography findings compatible with bronchitis and/or bronchiolitis, and one had tomographic signs of chronicity.

CONCLUSION

In this series of neutropenic patients with severe influenza H1N1 infection, chest computed tomography demonstrated mainly moderate or severe parenchymatous disease, but bronchiolitis was not a common feature. These findings associated with febrile neutropenia should elicit a diagnosis of severe viral infection.

CT of viral lower respiratory tract infections in adults: comparison among viral organisms and between viral and bacterial infections

OBJECTIVE

We retrospectively compared the CT findings of consecutive viral and bacterial lower respiratory tract infections (LRTIs) to determine their imaging appearance and any definable differences among the causative viruses and between the viral and bacterial infections.

MATERIALS AND METHODS

Imaging features of LRTI caused by influenza virus, respiratory syncytial virus (RSV), parainfluenza, adenovirus, and bacteria over a 33-month period were reviewed by three radiologists blinded to clinical and diagnostic information. Individual CT features and the dominant pattern of infection were recorded for each examination. Imaging characteristics were compared among the four respiratory viruses and between viral and bacterial infections.

RESULTS

One hundred fifteen chest CT scans were analyzed (60 influenza virus, 19 RSV, 10 adenovirus, four parainfluenza virus, and 22 bacterial pneumonia LRTIs). Individual imaging findings and imaging patterns were seen in similar frequencies when we compared viral and bacterial LRTIs, with the exception of the diffuse airspace pattern, which was seen more frequently in bacterial infections. Although there was overlap in the imaging appearance of individual viruses, RSV and adenovirus tended to have characteristic imaging appearances. RSV presented with an airway-centric pattern of disease (13/19 cases [68%]) characterized by varying mixtures of tree-in-bud opacities and bronchial wall thickening, with or without peribronchiolar consolidation. Adenovirus typically appeared as multifocal consolidation or ground-glass opacity without airway inflammatory findings (7/10 cases [70%]).

CONCLUSION

There is considerable overlap in the imaging appearance of viral and bacterial respiratory infections. However, some characteristic differences can be seen, especially with RSV and adenovirus infections.

Pneumonia induced by swine-origin influenza A (H1N1) infection: chest computed tomography findings in children

PURPOSE

The purpose of this study was to determine the features of chest computed tomography (CT) in children with swine-origin influenza A (H1N1) virus (S-OIV).

MATERIALS AND METHODS

The study population consisted of 16 children with laboratory-confirmed S-OIV infection (12 boys, 4 girls), with an age range of 5-10 years (mean 6.3 years). Pneumonia was suspected in these patients based on clinical features or confirmed by radiography. All subjects underwent CT for close evaluation of pneumonia, including characteristics, distribution, extent, and other findings such as pleural effusion, pneumothorax, and pneumomediastinum.

RESULTS

The predominant CT finding was consolidation plus ground-grass opacity (GGO) (11/16, 69%). The consolidation-dominant pattern was found in 10 of 16 (66%) patients, and 1 (6%) was GGO-dominant. One (6%) had only GGO. In all, 7 of the 16 patients had segmental or lobar consolidation. Abnormal opacities were primarily distributed in the central lung zone (8/16, 50%) and were multifocal (15/16, 94%). Four showed atelectasis (4/16, 25%). Pneumomediastinum was observed in 4 of 16 (25%). One patient had negative radiographic findings but was positive on CT.

CONCLUSION

Multifocal consolidation with central distribution is a common CT finding in children with S-OIV, but there are few GGO-dominant cases. Widespread consolidation (segmental or lobar) is also common.

Pneumonia complicating pandemic (H1N1) 2009: risk factors, clinical features, and outcomes

We performed an observational analysis of a prospective cohort of adults hospitalized for pandemic (H1N1) 2009 at 13 Spanish hospitals, from June to November 2009, to determine the risk factors, clinical features, and outcomes of pneumonia. Of 585 patients requiring hospitalization, chest radiography was obtained in 542. A total of 234 (43.1%) patients had pneumonia, of whom 210 underwent bacterial microbiologic studies. Of these patients, 174 (82.8%) had primary viral pneumonia and 36 (17.2%) had concomitant/secondary bacterial pneumonia. Bilateral pneumonia occurred in 48.3% of patients. Streptococcus pneumoniae was the most frequent pathogen among patients with bacterial pneumonia (26 of 36 patients). None of them had received pneumococcal vaccine. Compared with patients without pneumonia, those with pneumonia more frequently had shock during hospitalization (9.8% vs. 1%; p < 0.001), required intensive care unit admission (22.6% vs. 5.8%; p < 0.001), underwent mechanical ventilation (17.9% vs. 3.2%; p < 0.001), and had longer length of hospital stay (median, 7 d vs. 5 d; p < 0.001). In-hospital mortality was higher in patients with pneumonia than in the others (5.2% vs. 0%; p < 0.001). Absence of comorbid conditions (odds ratio [OR], 2.07; 95% confidence interval [CI], 1.32-3.24) was found to be an independent risk factor for pneumonia, whereas early (≤ 48 h) oseltamivir therapy (OR, 0.29; 95% CI, 0.19-0.46) was a protective factor. In conclusion, pneumonia is a frequent complication among adults hospitalized for pandemic (H1N1) 2009 and causes significant morbidity. Mortality in pandemic (H1N1) 2009 is low, but occurs mainly in patients with pneumonia. Early oseltamivir therapy is a protective factor for this complication.

Computer-assisted detection of infectious lung diseases: a review

Respiratory tract infections are a leading cause of death and disability worldwide. Although radiology serves as a primary diagnostic method for assessing respiratory tract infections, visual analysis of chest radiographs and computed tomography (CT) scans is restricted by low specificity for causal infectious organisms and a limited capacity to assess severity and predict patient outcomes. These limitations suggest that computer-assisted detection (CAD) could make a valuable contribution to the management of respiratory tract infections by assisting in the early recognition of pulmonary parenchymal lesions, providing quantitative measures of disease severity and assessing the response to therapy. In this paper, we review the most common radiographic and CT features of respiratory tract infections, discuss the challenges of defining and measuring these disorders with CAD, and propose some strategies to address these challenges.

Radiological prognostic factors in patients with pandemic H1N1 (pH1N1) infection requiring hospital admission

The aim of this study was to determine the radiologic findings associated with admission to the intensive care unit (ICU) and the development of acute respiratory distress syndrome (ARDS) in patients with pH1N1 infection. One hundred and four patients (15-96 years) with laboratory-confirmed pH1N1 infection seen at the Emergency Department from July to December 2009 who underwent chest radiographs were studied. Radiographs were evaluated for consolidation, ground-glass opacities, interstitial patterns, distribution, and extent of findings. Eighty-seven (83.7%) of the patients were managed in the ward, and 17 (16.3%) patients eventually required admission to the ICU. All patients admitted to the ICU showed abnormalities on the initial radiograph. The presence of consolidation, multifocal, diffuse, and bilateral involvement on the initial radiograph was associated with a statistically higher risk of requiring ICU admission (p<0.001). There were no significant differences regarding age, sex, and presence of underlying comorbidities. Evolution to ARDS was found in eight cases that necessitated ICU care. All of them had on the initial radiograph patchy multifocal consolidations (p<0.001) with bilateral lesions in six cases. A higher number of lung zones involved and consolidation on the initial chest radiograph as well as a rapid progression of the radiological abnormalities were identified in patients requiring ICU admission and development of ARDS. Initial chest radiographs show acute abnormalities in all patients with severe disease. The findings of a multifocal patchy consolidation pattern with bilateral or diffuse lung involvement on admission should alert of the impending severity of disease and the risk of necessitating ICU admission.

Chest imaging findings in hospitalized patients with H1N1 influenza

BACKGROUND

Previous studies have reported chest radiographic findings of consolidation and ground-glass opacity in patients with swine-origin influenza A (H1N1). However, most of these studies include both hospitalized and outpatients.

PURPOSE

To evaluate initial chest radiographic and CT findings of hospitalized swine flu patients, adults and children, confirmed with a real-time reverse transcriptase polymerase chain reaction (PCR) assay for H1N1 virus.

MATERIAL AND METHODS

All PCR-verified swine flu patients admitted to the Department of Emergency Medicine (October 1 to December 15, 2009) at Oulu University Hospital, in Northern Finland, who underwent frontal chest radiography within 24 hours of presentation and who were hospitalized, were included. The radiographs and CT scans were assessed for the presence of pneumonia and characterized by pattern and distribution. The patients' medical records were analyzed for demographics, underlying medical conditions, the admission to the intensive care unit (ICU), initiation of mechanical ventilation or non-invasive ventilation support (NIV) and death.

RESULTS

Of 159 H1N1 influenza patients, 135 (85%) underwent chest radiographs at admission; 113 adults and 22 children. Findings of pulmonary infiltrates were detected in 62% (70/113) of adults and 64% (14/22) of children, being bilateral in 67% of adults and 64% of the children. The anatomic location of infiltrates was more often peripheral in adults; 42/70 (60%) vs. 4/14 (29%), P = 0.041, and diffuse among children; 9/14 (64%) vs. 26/70 (37%), P = 0.078. When the ICU and NIV patients were compared to less severe cases, on their chest radiographs four or five lobes were more often affected (65%, 11/17 vs. 34% 23/67, P = 0.029 ). The predominant radiographic findings were consolidation (93% of all patients, 91% of adults and 100% of children) and ground-glass opacity (74% of all, 77% of adults and 57% of children). Pulmonary emboli were detected by CT in 2/9 (22%) patients.

CONCLUSION

The pandemic 2009 swine influenza causes common and widely distributed infiltrates on chest radiographs among hospitalized patients, which are not peculiar to usual respiratory viral infections, and these findings can not be differentiated from usual bacterial pneumonia.