Swine-origin influenza a (H1N1) viral infection in children: initial chest radiographic findings

Pediatric Lower Respiratory Tract Infections: Imaging Guidelines and Recommendations

Lower respiratory tract infection (LRTI) remains a major cause of morbidity and mortality in children. Various organisms cause LRTI, including viruses, bacteria, fungi, and parasites, among others. Infections caused by 2 or more organisms also occur, sometimes enhancing the severity of the infection. Medical imaging helps confirm a diagnosis but also plays a role in the evaluation of acute and chronic sequelae. Medical imaging tests help evaluate underlying pathology in pediatric patients with recurrent or long-standing symptoms as well as the immunocompromised.

Comparison of chest radiography and chest CT for evaluation of pediatric COVID-19 pneumonia: Does CT add diagnostic value?

PURPOSE

First, to investigate the added diagnostic value of chest computed tomography (CT) for evaluating COVID-19 in symptomatic children by comparing chest CT findings with chest radiographic findings, and second, to identify the imaging signs and patterns on CT associated with COVID-19 pneumonia in children.

MATERIALS AND METHODS

From March 2020 to December 2020, 56 consecutive children (33 males and 23 girls; mean age ± SD, 14.8 ± 5.0 years; range, 9 months-18 years) with mild to moderate symptom and laboratory confirmed COVID-19 (based on Centers for Disease Control criteria) underwent both chest radiography and chest CT on the same day within the first 2 days of initial presentation to the hospital. Two experienced radiologists independently evaluated chest radiographs and chest CT studies for thoracic abnormalities. The findings from chest radiography and chest CT were compared to evaluate the added diagnostic value of chest CT for affecting patient management. Interobserver agreement was measured with Cohen's κ statistics.

RESULTS

Eleven (19.6%) of 56 patients had abnormal chest radiographic findings, including ground-glass opacity (GGO) in 5/11 (45.4%) and combined GGO and consolidation in 6/11 (54.5%). On chest CT, 26 (46.4%) of 56 patients had abnormal CT findings, including combined GGO and consolidation in 19/26 (73.1%), GGO in 6/26 (23.1%), and consolidation in 1/26 (3.8%). Chest CT detected all thoracic abnormalities seen on chest radiography in 11/26 (42.3%) cases. In 15/26 (57.7%), chest CT detected lung abnormalities that were not observed on chest radiography, which included GGO and consolidation in 9/15 (60%), GGO in 5/15 (33.3%), and consolidation in 1/15 (6.6%) cases. These additional CT findings did not affect patient management. In addition, chest CT detected radiological signs and patterns, including the halo sign, reversed halo sign, crazy paving pattern, and tree-in-bud pattern. There was almost perfect interobserver agreement between the two reviewers for detecting findings on both chest radiographs (κ, 0.89, p = .001) and chest CT (κ, 0.96, p = .001) studies.

CONCLUSION

Chest CT detected lung abnormalities, including GGO and/or consolidation, that were not observed on chest radiography in more than half of symptomatic pediatric patients with COVID-19 pneumonia. However, these additional CT findings did not affect patient management. Therefore, CT is not clinically indicated for the initial evaluation of mild to moderately symptomatic pediatric patients with COVID-19 pneumonia.

Practical guide for pediatric pulmonologists on imaging management of pediatric patients with COVID-19

Understanding of coronavirus disease 2019 is rapidly evolving with new articles on the subject daily. This flood of articles can be overwhelming for busy practicing clinicians looking for key pieces of information that can be applied in daily practice. This review article synthesizes the reported imaging findings in pediatric Coronavirus disease 2019 (COVID-19) across the literature, offers imaging differential diagnostic considerations and useful radiographic features to help differentiate these entities from COVID-19, and provides recommendations for requesting imaging studies to evaluate suspected cases of pediatric COVID-19.

Pediatric SARS, H1N1, MERS, EVALI, and Now Coronavirus Disease (COVID-19) Pneumonia: What Radiologists Need to Know

OBJECTIVE. The purpose of this article is to review new pediatric lung disorders-including disorders that have occurred in recent years years such as severe acute respiratory syndrome (SARS), swine-origin influenza A (H1N1), Middle East respiratory syndrome (MERS), e-cigarette or vaping product use-associated lung injury (EVALI), and coronavirus disease (COVID-19) pneumonia-to enhance understanding of the characteristic imaging findings. CONCLUSION. Although the clinical symptoms of SARS, H1N1, MERS, EVALI, and COVID-19 pneumonia in pediatric patients may be nonspecific, some characteristic imaging findings have emerged or are currently emerging. It is essential for radiologists to have a clear understanding of the characteristic imaging appearances of these lung disorders in pediatric patients to ensure optimal patient care.

International Expert Consensus Statement on Chest Imaging in Pediatric COVID-19 Patient Management: Imaging Findings, Imaging Study Reporting, and Imaging Study Recommendations

Coronavirus disease 2019 (COVID-19) has quickly spread since it was first detected in December 2019 and has evolved into a global pandemic with over 1.7 million confirmed cases in over 200 countries around the world at the time this document is being prepared. Owing to the novel nature of the virus and the rapidly evolving understanding of the disease, there is a great deal of uncertainty surrounding the diagnosis and management of COVID-19 pneumonia in pediatric patients. Chest imaging plays an important role in the evaluation of pediatric patients with COVID-19; however, there is currently little information available describing imaging manifestations of COVID-19 in pediatric patients and even less information discussing the utilization of imaging studies in pediatric patients. To specifically address these concerns, a group of international experts in pediatric thoracic imaging from five continents convened to create a consensus statement describing the imaging manifestations of COVID-19 in the pediatric population, discussing the potential utility of structured reporting during the COVID-19 pandemic, and generating consensus recommendations for utilization of chest radiographs and CT in the evaluation of pediatric patients with COVID-19. The results were compiled into two structured reporting algorithms (one for chest radiographs and one for chest CT) and eight consensus recommendations for the utilization of chest imaging in pediatric COVID-19 infection. © RSNA, 2020.

Pediatric Chest Radiographic and CT Findings of Electronic Cigarette or Vaping Product Use-associated Lung Injury (EVALI)

Background Electronic cigarette or vaping product use-associated lung injury (EVALI) is a serious public health concern with substantial morbidity and mortality, particularly in young individuals. Purpose To evaluate chest radiographic and chest CT findings of EVALI in the pediatric population. Materials and Methods This was a retrospective study of children who presented to a tertiary pediatric hospital from December 2018 to December 2019. Patients fulfilled the Centers for Disease Control and Prevention criteria for EVALI and had chest radiographs and CT images available at initial presentation. Two pediatric radiologists independently reviewed imaging for pattern, distribution, and extent of pulmonary abnormalities, as well as for extrapulmonary abnormalities. Clinical information, management, and outcomes were reviewed. Interobserver agreement was measured with Cohen κ coefficient. Results Seven male patients (50%) and seven female patients (50%) (mean age, 16 years; range, 13-18 years) were evaluated. All patients underwent chest radiography and CT within 4 days of presentation (range, 0-4 days). Chest radiographic findings included ground-glass opacity in 14 of 14 (100%) and consolidation in eight of 14 (57%). CT findings included ground-glass opacity in 14 of 14 (100%), consolidation in nine of 14 (64%), and interlobular septal thickening in two of 14 (14%). At CT, subpleural sparing was seen in 11 of 14 (79%) and a reversed halo sign was seen in five of 14 (36%). Chest radiographic and CT abnormalities were predominately bilateral in 14 of 14 (100%) and symmetric in 13 of 14 (93%), with lower lobe predominance in seven of 14 (50%). Extent of abnormality was predominately diffuse at both chest radiography and CT. There was almost perfect interobserver agreement between two reviewers for detecting abnormalities on chest radiographs (κ = 0.99; 95% confidence interval: 0.97, 1.00) and CT (κ = 0.99; 95% confidence interval: 0.98, 1.00). Conclusion In pediatric patients, electronic cigarette or vaping product use-associated lung injury is characterized by bilateral symmetric ground-glass opacities, consolidation, and a lower lobe predominance at CT. © RSNA, 2020.

A paediatric influenza update 100 years after the Skyros island Spanish flu outbreak

This year marks the 100th anniversary of the 1918 Spanish flu outbreak on the Greek Aegean Sea island of Skyros, which devastated its population in less than 30 days. According to Constantinos Faltaits's annals published in 1919, the influenza attack on the island of Skyros commenced acutely ‘like a thunderbolt’ on the 27th of October, 1918 and was exceptionally severe and fatal. At that time, the viral cause of the influenza had not been detected, while the total number of victims of the Spanish flu outbreak has been estimated to have surpassed 50 million, worldwide. Almost one century after this Aegean Sea island's tragedy, the ‘4th Workshop on Paediatric Virology’, organised on the 22nd of September, 2018 in Athens, Greece, was dedicated to the 100 years of the ‘Spanish’ flu pandemic. This review article highlights the plenary and key lectures presented at the workshop on the recent advances on the epidemiology, clinical management and prevention of influenza in childhood.

Initial chest X-ray findings in pediatric patients diagnosed with H1N1 virus infection

Objective

To evaluate chest X-ray findings in pediatric patients diagnosed with influenza A (H1N1) virus infection.

Materials and Methods

We retrospectively reviewed chest X-ray findings in 17 cases of pulmonary infection with the H1N1 virus (in 7 males and 10 females) examined between 2012 and 2016. The mean age of the patients was 14 months (range, 2-89 months). The diagnosis was established on the basis of clinical and radiographic criteria, and the virus was detected by polymerase chain reaction. The radiographic findings were categorized by type/pattern of opacity and by lung zone. The patients were divided into two groups: those not requiring ventilatory support; and those requiring ventilatory support or evolving to death.

Results

The abnormality most often seen on chest X-rays was that of peribronchovascular opacities, the majority of which affected less than 25% of the lung, the involvement being bilateral and asymmetric. The lung zone most frequently involved was the middle third, with central and peripheral distribution, without pleural effusion. There was a statistically significant difference between the groups in terms of the symmetry of pulmonary involvement, asymmetric findings predominating in the group that required ventilatory support (p = 0.029).

Conclusion

In pediatric patients with H1N1 virus infection, the main alterations on the initial chest X-rays are peribronchovascular opacities, nonspecific alveolar opacities, and consolidations. Although the definitive diagnosis of H1N1 virus infection cannot be made on the basis of imaging characteristics alone, using a combination of clinical and radiographic findings can substantially improve the diagnostic accuracy.

Influenza A (H1N1)

In March 2009, an outbreak of human-infected swine influenza occurred in Mexico, with reports of deaths. Soon afterward, such cases were reported worldwide, namely, a pandemic outbreak. The prevailing disease is then defined as an acute respiratory infectious disease caused by swine-origin influenza A (H1N1) virus, a new variant of influenza virus. Its viral strains contain gene segments of three types of influenza viruses, namely swine influenza virus, avian influenza virus and human influenza virus. And the virus is mainly transmitted among humans via direct and indirect contact or respiratory tract.

The radiological diagnosis of pneumonia in children

Despite the importance of paediatric pneumonia as a cause of short and long-term morbidity and mortality worldwide, a reliable gold standard for its diagnosis remains elusive. The utility of clinical, microbiological and radiological diagnostic approaches varies widely within and between populations and is heavily dependent on the expertise and resources available in various settings. Here we review the role of radiology in the diagnosis of paediatric pneumonia. Chest radiographs (CXRs) are the most widely employed test, however, they are not indicated in ambulatory settings, cannot distinguish between viral and bacterial infections and have a limited role in the ongoing management of disease. A standardised definition of alveolar pneumonia on a CXR exists for epidemiological studies targeting bacterial pneumonias but it should not be extrapolated to clinical settings. Radiography, computed tomography and to a lesser extent ultrasonography and magnetic resonance imaging play an important role in complicated pneumonias but there are limitations that preclude their use as routine diagnostic tools. Large population-based studies are needed in different populations to address many of the knowledge gaps in the radiological diagnosis of pneumonia in children, however, the feasibility of such studies is an important barrier.

Initial radiographic features as outcome predictor of adult respiratory syncytial virus respiratory tract infection

OBJECTIVE

The purposes of this study were to evaluate the chest radiographic features of adult patients hospitalized for respiratory syncytial virus respiratory tract infections and to assess whether initial chest radiographic findings help predict clinical outcome.

MATERIALS AND METHODS

All adult patients hospitalized from January 2009 to December 2011 with laboratory-confirmed respiratory syncytial virus infection were included in the study. Patient clinical data and admission chest radiographs were retrospectively reviewed. Adverse outcomes included need for supplemental oxygen, need for assisted ventilation, and death.

RESULTS

Of 285 patients (mean age, 74 ± 16 years) included, 199 (69.8%) had abnormal chest radiographic findings: 49.5% (141/285) had acute changes, and 47.7% (136/285) had chronic changes. Consolidation (68/141 [48.2%]) and ground-glass opacity (57/141 [40.4%]) were the predominant types of acute changes and were most common in unilateral single-lower-zone involvement. Consolidation, ground-glass opacity, and chronic changes occurred with significantly higher frequency in patients with adverse outcomes. The presence of acute (odds ratio, 3.6) and chronic (odds ratio, 2.2) changes were independent risk factors for mortality.

CONCLUSIONS

A large proportion of adult patients hospitalized with respiratory syncytial virus respiratory tract infection had changes on initial chest radiographs. Consolidation or ground-glass opacity in a unilateral single-lower-zone distribution were the most common findings. The presence of acute and chronic radiographic lung changes was associated with adverse outcomes.

Response to sorafenib in a pediatric patient with papillary thyroid carcinoma with diffuse nodular pulmonary disease requiring mechanical ventilation

BACKGROUND

Papillary thyroid cancer (PTC) presents with local and distant metastases more frequently in children than in adults. However, hypoxemia secondary to pulmonary metastases has not been reported in the literature. Sorafenib is a small-molecule multikinase inhibitor used in radioactive iodine ((131)I)-refractive papillary thyroid carcinoma.

PATIENT FINDINGS

An eight-year-old boy presented with fever and hypoxemia and was found to have H1N1 viral pneumonia requiring mechanical ventilation and antiviral and glucocorticoid treatment. After initial improvement, he was readmitted one month later because of persistent hypoxemia. A high-resolution computed tomography of the chest and neck revealed multiple 1-4 mm nodules and necrotic lymph nodes on the right side of the neck. Left lung wedge resection and right deep cervical node biopsies were consistent with PTC. He underwent a total thyroidectomy with a central neck node dissection and postoperatively required prolonged mechanical ventilation. Due to the inability to be weaned from mechanical ventilation, treatment with sorafenib 200 mg daily (10 mg/kg/day, 250 mg/m(2)) was initiated. Eight days thereafter, ventilation support was discontinued and the child was extubated. However, he failed extubation secondary to supraglottic edema, and seven days later tracheostomy was performed. The dosage of sorafenib was increased to 200 mg twice daily (20 mg/kg/day, 500 mg/m(2)). After 52 days of therapy, a repeat computed tomography scan showed reduction in the lung nodule size to 1-2 mm. He underwent (131)I therapy 87 days after sorafenib was started. A post-treatment scan showed extensive uptake throughout the lungs and thyroid bed, supraclavicular nodes, and cervical nodes.

CONCLUSIONS

This is the first reported case of a pediatric patient with respiratory failure possibly secondary to diffuse micronodular PTC requiring mechanical ventilation and subsequent delay in definitive therapy. Sorafenib could be considered for gap therapy when (131)I therapy cannot be administered in a timely manner. Treatment with this multikinase inhibitor does not seem to adversely affect the uptake of (131)I in radiation-naïve patients.

Infections

Lower respiratory tract infection is a very common illness in children and is a significant cause of morbidity and mortality. Clinical signs and symptoms are nonspecific especially in infants and younger children and some even present with nonrespiratory complaints. Infectious agents causing pneumonia is not limited to viruses and bacteria, but it could also be due to Mycoplasma, Mycobacteria, fungi, protozoa, and parasites. Coinfection with two or more microbial agents can also occur. The etiologic agent of lower respiratory infection in a child is often difficult to obtain, but the patient’s age can help narrow the possible cause. Microbiological tests are important but could be difficult to obtain especially in younger children. Various medical imaging modalities not only play an important role as an aid in diagnosis but can also help during and after therapy. Imaging can also help evaluate complications to pneumonia and exclude other causes of respiratory distress including underlying developmental anomalies, foreign body, gastroesophageal reflux disease, and aspiration. In this chapter, the imaging modalities utilized in the detection of pulmonary infections will be discussed. The spectrum of typical imaging findings for various etiologic agents in both immunocompetent and immunocompromised children will be presented.

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.

Clinical characteristics and outcomes in hospitalized patients with respiratory viral co-infection during the 2009 H1N1 influenza pandemic

Background

The clinical consequences of co-infection with two or more respiratory viruses are poorly understood. We sought to determine if co-infection with pandemic 2009–2010 influenza A H1N1 (pH1N1) and another respiratory virus was associated with worse clinical outcomes.

Methods

A retrospective cohort study was performed of all hospitalized patients with a positive respiratory viral panel (RVP) for two or more viruses within 72 hours of admission at our institution from October 2009 to December 2009. We compared patients infected with one respiratory virus to those with respiratory viral co-infection.

Results

We identified 617 inpatients with a positive RVP sample with a single virus and 49 inpatients with a positive RVP sample for two viruses (i.e. co-infection). Co-infected patients were significantly younger, more often had fever/chills, tachypnea, and they more often demonstrated interstitial opacities suggestive of viral pneumonia on the presenting chest radiograph (OR 7.5, 95% CI 3.4–16.5). The likelihood of death, length of stay, and requirement for intensive care unit level of care were similar in both groups, but patients with any respiratory virus co-infection were more likely to experience complications, particularly treatment for a secondary bacterial pneumonia (OR 6.8, 95% CI 3.3–14.2). Patients co-infected with pH1N1 and another respiratory virus were more likely to present with chest radiograph changes suggestive of a viral pneumonia, compared to mono-infection with pH1N1 (OR 16.9, 95% CI 4.5–62.7). By logistic regression using mono-infection with non-PH1N1 viruses as the reference group, co-infection with pH1N1 was the strongest independent predictor of treatment for a secondary bacterial pneumonia (OR 17.8, 95% CI 6.7–47.1).

Conclusion

Patients with viral co-infection, particularly with pH1N1, were more likely to have chest radiograph features compatible with a viral pneumonia and complications during their hospital course, particularly treatment for secondary bacterial pneumonia. Despite this, co-infection was not associated with ICU admission.

Utility of salivagram in pulmonary aspiration in pediatric patients: comparison of salivagram and chest radiography

OBJECTIVE

The purpose of our study was to correlate the results of the radionuclide salivagram with the corresponding chest radiography findings on patients being evaluated for salivary aspiration to determine the utility of the salivagram.

MATERIALS AND METHODS

We identified 222 patients younger than 21 years who underwent salivagram and chest radiography within 3 months of each other. Salivagrams were blindly interpreted by two readers and chest radiographs were blindly interpreted by two other readers. The kappa coefficient with 95% CI was used to measure the level of interobserver agreement. Multivariate logistic regression was applied to determine whether age, sex, and neurologic diagnosis were predictors of a positive salivagram, with the odds ratio used to estimate association.

RESULTS

Interobserver agreement on salivagram interpretation was excellent (κ = 0.988; p < 0.0001; 95% CI, 0.968-1.000). Interobserver agreement on chest radiography interpretation was excellent (κ = 0.905; p < 0.0001; 95% CI, 0.845-0.965). The salivagram was positive for aspiration in 55 patients (25%). Chest radiography was positive in 54 patients (24%). When the interpretations of the salivagram (normal or abnormal) were compared with interpretations of the chest radiograph (normal or abnormal), there were 213 agreements and nine disagreements (intermethod agreement κ = 0.891; p < 0.0001; 95% CI, 0.831-0.952). Independent of age (p = 0.80) and sex (p = 0.31), patients with a neurologic diagnosis had odds of a positive salivagram 5.6 times higher than other diagnoses (odds ratio = 5.6; 95% CI, 2.5-13.1; p < 0.0001).

CONCLUSION

Infants with abnormal findings on salivagrams also had a high rate of abnormal findings on chest radiographs, which may indicate that some of the lung disease may be due to aspirated saliva. Salivagrams may be useful in children at risk of aspiration to identify those in whom intervention may help minimize the consequences of aspiration.

Comparing the clinical severity of the first versus second wave of 2009 Influenza A (H1N1) in a New York City pediatric healthcare facility

OBJECTIVE

We previously reported the epidemiology of 2009 Influenza A (H1N1) in our pediatric healthcare facility in New York City during the first wave of illness (May-July 2009). We hypothesized that compared with the first wave, the second wave would be characterized by increased severity of illness and mortality.

DESIGN

: Case series conducted from May 2009 to April 2010.

SETTING

Pediatric emergency departments and inpatient facilities of New York-Presbyterian Hospital.

PATIENTS

All hospitalized patients ÷ 18 yrs of age with positive laboratory tests for influenza A.

MEASUREMENTS AND MAIN RESULTS

We compared severity of illness during the first and second wave assessed by the number of hospitalized children, including those in the pediatric intensive care unit, bacterial superinfections, and mortality rate. Compared to the first wave, fewer children were hospitalized during the second wave (n = 115 vs. 76), but a comparable portion were admitted to the pediatric intensive care unit (30.4% vs. 19.7%; p = .10). Pediatric Risk of Mortality III scores, length of hospitalization in the pediatric intensive care unit, incidence of respiratory failure and pneumonia, and peak oxygenation indices were similar during both waves. Bacterial superinfections were comparable in the first vs. second wave (3.5% vs. 1.3%). During the first wave, no child received extracorporeal membrane oxygenation and one died, while during the second wave, one child received extracorporeal membrane oxygenation and there were no deaths.

CONCLUSIONS

At our pediatric healthcare facility in New York City, fewer children were hospitalized with 2009 Influenza A (H1N1) during the second wave, but both waves had a similar spectrum of illness severity and low mortality rate.

Initial HRCT findings of novel influenza A (H1N1) infection

OBJECTIVES

The aim of our study was to describe the presentation and illustrate the imaging features of chest high-resolution computed tomography (HRCT) of patients with novel influenza A (H1N1) virus infection.

METHODS

Data were collected from 163 hospitalized patients between November 2009 and March 2011, who fulfilled the clinical criteria for H1N1 influenza infection and underwent HRCT examinations within 24 hours of admission.

RESULTS

Abnormal findings were observed in 40.5% of the patients. The patients with positive imaging findings were significantly older than patients with normal HRCT findings (P=0.02). The most common finding was ground-glass opacity (GGO) (n=35). Interlobular septal thickening (n=31) and centrilobular nodules (n=30) were the second most frequent findings. Other common findings were consolidation, reticulation, and linear shadow. The most common imaging finding for lung involvement was GGO with a patchy pattern. Pulmonary involvement of the disease may be extensive and variable, but the total volume of affected lung was mostly <1 lobe.

CONCLUSION

The baseline HRCT may be valuable and suggestive even for non-severe H1N1 infections. When a severe case or a evolution is suspected, chest CT could be essential both for determining the precise extent of parenchymal damage and for monitoring its evolution.

H1N1 pneumonia: our experience in 50 patients with a severe clinical course of novel swine-origin influenza A (H1N1) virus (S-OIV)

PURPOSE

The authors reviewed chest radiographs (CXR) and thin-section computed tomography (CT) findings of pulmonary complications in a selected population of 50 consecutive patients with severe novel swine-origin influenza A (H1N1) virus (S-OIV) pneumonia who were seen at the Subintensive Respiratory Unit (UTSIR) and at the Intensive Care Unit (ICU) at Monaldi Hospital, Naples, Italy.

MATERIALS AND METHODS

CXR and CT findings of 50 patients who fulfilled the World Health Organisation (WHO) criteria for S-OIV infection were reviewed by four radiologists. The final study group of 50 patients was divided into two subgroups on the basis of clinical course: group 1 consisted of 42 patients requiring noninvasive mechanical ventilation and admitted to the UTSIR; group 2 consisted of eight patients who required ICU admission and extracorporeal membrane oxygenation or advanced mechanical ventilation from October 2009 to December 2009. All patients underwent CXR and thin-section multidetector CT (MDCT) scan; the initial and follow-up radiographs and CT scans were evaluated for the presentation and follow-up pattern (consolidation, ground-glass opacities, nodules, reticulation), distribution and extent of abnormality.

RESULTS

All patients had radiological signs of pulmonary involvement. Ground-glass opacity and consolidation, which was mainly peripheral, was the most frequent finding. In three patients, we report for the first time in viral pneumonia the reversed halo sign. Lesion extent was related to aggressiveness of the illness. More often, both lungs were involved (82%). Thoracic comorbidity was present in 18% of patients; 22% of patients was obese, and in this group, the clinical course was more aggressive than in the others with the same lesion extent at imaging. Furthermore, superinfection led to worsening of the clinical conditions.

CONCLUSIONS

The most common CXR and CT findings in patients with S-OIV infection were unilateral or bilateral ground-glass opacities with or without associated focal or multifocal areas of consolidation. On MDCT, ground-glass opacities and areas of consolidation had a predominant peribronchovascular and subpleural distribution, resembling organising pneumonia; they progressed to bilateral extensive airspace disease in severely ill patients.

Characterization of 2009 H1N1 pandemic influenza in a population of Dutch children with influenza-like signs and symptoms

Aim:  To determine causative respiratory pathogens and describe epidemiological and clinical characteristics in a paediatric population with influenza‐like illness during the 2009 H1N1‐pandemic.

Methods:  Observational study of 412 children visiting an outpatient clinic of a Dutch teaching hospital.

Results:  From August to December 2009, 412 children were tested at the clinic; 32% proved H1N1‐positive, confirmed by reverse‐transcriptase‐polymerase‐chain‐reaction (RT‐PCR). Pathogens were detected in 65% of samples. Influenza A(H1N1) (n = 132), human rhinovirus (n = 55), respiratory syncytial virus (n = 45) and adenovirus (n = 34) were mostly identified. Co‐infections were seen in 34 children (8.3%). Mean age was 6.8 and 4.2 years in H1N1‐positive and H1N1‐negative cases, respectively (p < 0.01). H1N1‐positive outpatient children reported fever, cough and rhinorrhoea more frequently than their H1N1‐negative counterparts. Of 72 hospitalized children, 31% proved H1N1‐positive; all showed a relatively mild clinical illness. None of the children had been admitted to an intensive care unit or died. Oseltamivir treatment was initiated in 72 children and discontinued in 42 (63%) when RT‐PCR results turned negative.

Conclusion:  The 2009 H1N1‐pandemic showed a mild clinical course in a Dutch paediatric outpatient clinic population. Respiratory pathogens were detected in the majority of children with influenza‐like illness and influenza A(H1N1) virus was identified in one‐third. Testing symptomatic children during an influenza pandemic has effectively limited the use of oseltamivir.

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.

Evaluation of monkeypox disease progression by molecular imaging

Infection of nonhuman primates (NHPs) with monkeypox virus (MPXV) is currently being developed as an animal model of variola infection in humans. We used positron emission tomography and computed tomography (PET/CT) to identify inflammatory patterns as predictors for the outcome of MPXV disease in NHPs. Two NHPs were sublethally inoculated by the intravenous (IV) or intrabronchial (IB) routes and imaged sequentially using fluorine-18 fluorodeoxyglucose ((18)FDG) uptake as a nonspecific marker of inflammation/immune activation. Inflammation was observed in the lungs of IB-infected NHPs, and bilobular involvement was associated with morbidity. Lymphadenopathy and immune activation in the axillary lymph nodes were evident in IV- and IB-infected NHPs. Interestingly, the surviving NHPs had significant (18)FDG uptake in the axillary lymph nodes at the time of MPXV challenge with no clinical signs of illness, suggesting an association between preexisting immune activation and survival. Molecular imaging identified patterns of inflammation/immune activation that may allow risk assessment of monkeypox disease.

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.

Chest radiograph findings in children with laboratory confirmed pandemic H1N1 virus infection

INTRODUCTION

Since its onset in the spring of 2009, the H1N1 pandemic has kept health-care professionals busy worldwide. Even though it often causes respiratory tract illness, reports describing the radiological manifestations in infected children are few. The purpose of this study was twofold: to review the chest radiograph findings in children with laboratory-confirmed pandemic (H1N1) 2009 influenza virus and compare them with the chest radiographic findings in children with the same symptoms but laboratory negative.

METHODS

Informed consent was not required by the institutional review board for this retrospective study. We identified 151 children who were tested for pandemic H1N1 virus and had chest radiographs. Chest radiographs were evaluated for the presence of airway disease including hyperinflation, subsegmental atelectasis and peribronchial cuffing, airspace disease, pleural effusion or any combination of these, and compared for H1N1-positive and H1N1-negative children, for healthy and non-healthy children separately.

RESULTS

No statistically significant difference between H1N1-tested positive children and H1N1-tested negative children was found for the proportion of abnormal chest rays (P=1 for healthy children, P=0.08 for children with chronic disease). For individual findings, there was no difference between H1N1-tested positive healthy children and H1N1-tested negative healthy children (P>0.083 for each finding) In children with chronic disease, there was significantly more subsegmental atelectasis (P=0.037) in the radiographs of H1N1-tested negative children.

CONCLUSION

Chest radiographs have non-specific findings in cases of suspected swine flu in children and have limited value in distinguishing H1N1 from non-H1N1 viral infections for both healthy children and children with chronic disease.

Swine-origin influenza A viral (H1N1) infection in children: chest computed tomography findings

PURPOSE

The aim of this study was to review the chest computed tomography (CT) findings in children with swine-origin influenza (H1N1) virus (S-OIV) infection.

MATERIALS AND METHODS

The radiologists retrospectively reviewed chest CT findings in 12 children with S-OIV infection and recorded the following findings: ground-glass opacities (GGO), consolidation, nodules, reticular opacities, peribronchial cuffing, and air trapping; distribution; affected lobes. The presence of pleural effusions, pneumomediastinum, pulmonary interstitial emphysema (PIE), and lymphadenopathy was also recorded.

RESULTS

Chest CT revealed GGO (67%), consolidation (67%), nodules (25%), peribronchial cuffing (42%), and air trapping (33%). The distribution of the lesions was random (75%), peribronchial (17%), or subpleural (8%). The lobes affected were the lower (92%), upper (58%), and middle (17%) lobes. There were associated pleural effusions (42%), PIE (42%), pneumomediastinum (33%), and lymphadenopathy (75%). Among five patients with air-leak complications, three had a history of allergies and three required the intensive care unit.

CONCLUSION

Chest CT findings in children with S-OIV infection were peribronchial thickening and a mixture of airspace consolidation and GGO with random distribution and lower lobe predominance. Pleural effusion, lymphadenopathy, PIE, and pneumomediastinum may be associated findings.

Clinical characteristics and outcomes among pediatric patients hospitalized with pandemic influenza A/H1N1 2009 infection

Purpose

The purpose of this article is to describe the clinical and epidemiologic features and outcomes among children hospitalized with pandemic influenza A/H1N1 2009 infection.

Methods

We retrospectively reviewed the charts of hospitalized pediatric patients (<18 years) diagnosed with pandemic influenza A/H1N1 2009 infection by reverse-transcriptase polymerase chain reaction at a tertiary hospital in Seoul, Korea, between September 2009 and February 2010.

Results

A total of 72 children were hospitalized with pandemic influenza A/H1N1 2009 infection (median age, 6.0 years; range, 2 months to 18 years). A total of 40% had at least 1 underlying medical condition, including asthma (17%), malignancies (19%), and heart diseases (17%). Of the 72 patients, 54 (76%) children admitted with H1N1 infection showed radiographic alterations compatible with pneumonia. There was no significant difference in pre-existing conditions between pandemic influenza A/H1N1 infected patients with or without pneumonia. Children with pandemic influenza A/H1N1 pneumonia were more likely to have a lower lymphocyte ratio (P=0.02), higher platelet count (P=0.02), and higher level of serum glucose (P=0.003), and more commonly presented with dyspnea than did those without pneumonia (P=0.04).

Conclusion

No significant differences in age, sex, or presence of preexisting conditions were found between children hospitalized with pandemic influenza A/H1N1 H1N1 influenza infection with pneumonia and those without pneumonia. Higher leukocyte count, higher glucose level, and a lower lymphocyte ratio were associated with the development of pandemic A/H1N1 2009 influenza pneumonia.

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.

[Is H1N1 flu different from seasonal flu on initial plain chest films?]

OBJECTIVES

To determine whether there are differences in the findings on the initial plain chest films of patients with H1N1 influenza and those of patients with flu symptoms during the flu season.

MATERIAL AND METHODS

All patients underwent plain-film chest radiography in the Emergency Department for flu symptoms; 95 patients had H1N1 influenza confirmed between July 2009 and December 2009 and 95 patients were attended for symptoms of seasonal flu in January 2009. We analyzed the views obtained, the distribution and location of the radiologic findings, and patients' age, sex, and previous disease.

RESULTS

Patients with H1N1 influenza were younger than those with seasonal flu symptoms (mean 40.2 vs 50.9 years; p<0.001) and fewer had prior disease (48 vs. 63; p<0.001). Plain films were acquired with patients in the standing position in 75 patients in the H1N1 group and in 77 in the seasonal flu group; pathological findings were present in nearly 50% of the patients in each group. The most common findings in the H1N1 group were multifocal patchy consolidations (41.2%; p<0.001) and peribronchial-vascular opacities (16.3%), whereas in the seasonal flu group the most common finding was consolidation in a single lobe (43.9%).

CONCLUSION

We found significant differences between the radiologic findings of patients with H1N1 influenza (severe) and those of patients with symptoms of flu during the flu season: the incidence of multifocal patchy consolidation was greater in H1N1 patients and H1N1 patients were younger.

[Clinical features of influenza A H1N1 2009: a multicentre study]

OBJECTIVE

To describe clinical and epidemiological features of influenza A H1N1 2009 diagnosed patients in the Emergency Department of 4 hospitals.

MATERIAL AND METHODS

Prospective multicentre study conducted from july to december 2009. The patients diagnosed by Real-Time PCR of influenza A H1N1 2009 in the emergency department were included. The test was requested according to the protocols established throughout the epidemic. Epidemiological, clinical, laboratory variables and outcomes were evaluated.

RESULTS

A total of 456 cases were included, with a median age of 6.5years (PC(25-75) 3-10.6). There were risk factors of complications In 266 patients (59.4%) due to the influenza, mainly: respiratory (47%), cardiovascular (17%), neurological (14%) and immunosuppression (11%). The most frequent symptoms were fever (96%), (88%) cough, (72%) rhinorrhoea, muscle aches or asthenia and breathing difficulties and, less common, gastrointestinal and neurological symptoms. Chest X-ray was performed on 224 cases (49%), with lobar (31%) and interstitial (15%) infiltrates. One hundred and forty patients (31%) were hospitalised and 3.2% required Intensive Care Unit (median stay 4 and 3.5days, respectively). The most frequent complications were pneumonias and bronchospasms. Three patients died (a previously healthy patient with myocarditis and 2 patients with encephalopathy due to respiratory failure). Another case of myocarditis recovered with sequelae.

CONCLUSIONS

The profile of patient with influenza A 2009 diagnosed in the emergency department was a school child, with risk factors of complications, presenting with respiratory symptoms and fever over a short time, and who can be discharged. It is important to emphasise myocarditis, as well as the usual respiratory complications of influenza virus.

Pneumonia in the immunocompetent patient

Pneumonia is an acute inflammation of the lower respiratory tract. Lower respiratory tract infection is a major cause of mortality worldwide. Pneumonia is most common at the extremes of life. Predisposing factors in children include an under-developed immune system together with other factors, such as malnutrition and over-crowding. In adults, tobacco smoking is the single most important preventable risk factor. The commonest infecting organisms in children are respiratory viruses and Streptoccocus pneumoniae. In adults, pneumonia can be broadly classified, on the basis of chest radiographic appearance, into lobar pneumonia, bronchopneumonia and pneumonia producing an interstitial pattern. Lobar pneumonia is most commonly associated with community acquired pneumonia, bronchopneumonia with hospital acquired infection and an interstitial pattern with the so called atypical pneumonias, which can be caused by viruses or organisms such as Mycoplasma pneumoniae. Most cases of pneumonia can be managed with chest radiographs as the only form of imaging, but CT can detect pneumonia not visible on the chest radiograph and may be of value, particularly in the hospital setting. Complications of pneumonia include pleural effusion, empyema and lung abscess. The chest radiograph may initially indicate an effusion but ultrasound is more sensitive, allows characterisation in some cases and can guide catheter placement for drainage. CT can also be used to characterise and estimate the extent of pleural disease. Most lung abscesses respond to medical therapy, with surgery and image guided catheter drainage serving as options for those cases who do not respond.

Novel influenza A (H1N1) infection: chest CT findings from 21 cases in Seoul, Korea

AIM

To retrospectively evaluate the computed tomography (CT) appearances of novel influenza A (H1N1) infection.

MATERIALS AND METHODS

Chest CT images obtained at clinical presentation in 21 patients (eight men, 13 women; mean age, 37 years; age range, 6-82 years) with confirmed novel influenza A (H1N1) infection were assessed. The radiological appearances of pulmonary parenchymal abnormalities, distribution, and extent of involvement on initial chest CT images were documented. The study group was divided on the basis of age [group 1, patients <18 years old (n=8); group 2, patients ≥ 18 years old (n=13)]. Medical records were reviewed for underlying medical conditions and laboratory findings. The occurrence of recognizable CT patterns was compared for each group using the images from the initial CT examination.

RESULTS

The most common CT pattern observed in all patients was ground-glass attenuated (GGA) lesions (20/21, 95%). Bronchial wall thickening (9/21, 43%) was the second most common CT finding. Other common CT findings were consolidation (6/21, 29%), pleural effusion (6/21, 29%), pneumothorax or pneumomediastinum (5/21, 24%), and atelectasis (5/21, 24%). Among these, atelectasis and pneumomediastinum (pneumothorax) were only observed in group 1. The GGA lesions showed predilections for diffuse multifocal (10/20, 50%) or lower zone (8/20, 40%) distribution. Involvement of central lung parenchyma (12/20, 60%) was more common than a mixed peripheral and central pattern (6/20, 30%) or a subpleural pattern (2/20, 10%) at the time of presentation. Patchy GGA lesions were more frequent (18/20, 90%) than diffuse GGA lesions, and 75% (15/20) of these lesions had a bronchovascular distribution. Bilateral disease was present in all patients with GGA lesions. Bronchial wall thickening was predominantly centrally located and the distribution of the consolidation was non-specific.

CONCLUSION

The predominantly centrally located GGA lesions, with common multifocal or bilateral involvement, peribronchovascular distribution, and patchy appearance are the more distinctive CT findings of novel influenza A (H1N1) infection. Pneumomediastinum and atelectasis resulting from this disease are more common in young patients under the age of 18 years.

Novel influenza A (H1N1) virus infection in children: chest radiographic and CT evaluation

Objective

The purpose of this study was to evaluate the chest radiographic and CT findings of novel influenza A (H1N1) virus infection in children, the population that is more vulnerable to respiratory infection than adults.

Materials and Methods

The study population comprised 410 children who were diagnosed with an H1N1 infection from August 24, 2009 to November 11, 2009 and underwent chest radiography at Dankook University Hospital in Korea. Six of these patients also underwent chest CT. The initial chest radiographs were classified as normal or abnormal. The abnormal chest radiographs and high resolution CT scans were assessed for the pattern and distribution of parenchymal lesions, and the presence of complications such as atelectasis, pleural effusion, and pneumomediastinum.

Results

The initial chest radiograph was normal in 384 of 410 (94%) patients and abnormal in 26 of 410 (6%) patients. Parenchymal abnormalities seen on the initial chest radiographs included prominent peribronchial marking (25 of 26, 96%), consolidation (22 of 26, 85%), and ground-glass opacities without consolidation (2 of 26, 8%). The involvement was usually bilateral (19 of 26, 73%) with the lower lung zone predominance (22 of 26, 85%). Atelectasis was observed in 12 (46%) and pleural effusion in 11 (42%) patients. CT (n = 6) scans showed peribronchovascular interstitial thickening (n = 6), ground-glass opacities (n = 5), centrilobular nodules (n = 4), consolidation (n = 3), mediastinal lymph node enlargement (n = 5), pleural effusion (n = 3), and pneumomediastinum (n = 3).

Conclusion

Abnormal chest radiographs were uncommon in children with a swine-origin influenza A (H1N1) virus (S-OIV) infection. In children, H1N1 virus infection can be included in the differential diagnosis, when chest radiographs and CT scans show prominent peribronchial markings and ill-defined patchy consolidation with mediastinal lymph node enlargement, pleural effusion and pneumomediastinum.

Pandemic influenza A (H1N1) 2009: chest radiographic findings from 147 proven cases in the Montreal area

OBJECTIVE

To describe chest radiographic findings in patients with isolated and complicated acute novel influenza A (H1N1) virus infection.

METHODS

Retrospective study of 147 patients (64 men, mean age 41) with reverse-transcriptase polymerase chain reaction confirmed acute influenza A (H1N1) infection, who also had a chest radiograph <72 hours of viral specimen collection. Radiographs were analysed for acute findings. A correlation with bacterial cultures results was performed. The unpaired 2-sample equal-variance Student t test was applied to continuous variables and the Pearson χ(2) test of association to discrete variables.

RESULTS

In 71% of cases, chest radiograph was normal. The presence of acute imaging findings was associated with older age (P < .05), increased number of comorbidities (most commonly, chronic obstructive pulmonary disease, diabetes, asthma) (P < .05), higher rate of hospitalization (P < .05) and intensive care unit admission, and increased mortality. Predominant acute radiographic finding in isolated influenza A (H1N1) was alveolar opacity (88%), either unifocal or multifocal, most often in the lower lobes. In the subgroup of patients with positive imaging findings and for whom nonviral microbiologic data was available, 62% had superimposed bacterial or fungal infection.

CONCLUSION

In the majority of patients with acute influenza A (H1N1) infection, the chest radiograph is normal. Acute imaging findings are associated with older age, an increased number of comorbidities, and a higher rate of complications and mortality. The predominant radiographic finding of isolated primary influenza A (H1N1) infection is alveolar opacity. Superimposed bacterial infection is frequent and must be excluded in patients with abnormal imaging.