Radiological and clinical course of pneumonia in patients with avian influenza H5N1

Unusual pediatric lung infections: imaging findings

Pediatric lung infections continue to be a leading cause of pediatric morbidity and mortality. Although both pediatric and general radiologists are familiar with typical lung infections and their imaging findings in children, relatively rare lung infections continue to present a diagnostic challenge. In addition, the advances in radiological imaging and emergence of several new lung infections in recent years facilitated the need for up-to-date knowledge on this topic. In this review article, we discuss the imaging findings of pediatric lung infections caused by unusual/uncommon and new pathogens. We review the epidemiological, clinical, and radiological imaging findings of viral (coronavirus disease 2019, Middle East respiratory syndrome, bird flu), bacterial (Streptococcus anginosus, Francisella tularensis, Chlamydia psittaci), and parasitic lung infections (echinococcosis, paragonimiasis, amoebiasis). Additional disorders whose clinical course and imaging findings may mimic lung infections in children (hypersensitivity pneumonitis, pulmonary hemorrhage, eosinophilic pneumonia) are also presented, to aid in differential diagnosis. As the clinical presentation of children with new and unusual lung infections is often non-specific, imaging evaluation plays an important role in initial detection, follow-up for disease progression, and assessment of potential complications.

Emergent Pneumonia in Children

In recent decades there have been multiple pathogens, viruses and bacteria, which have emerged as causal agents of pneumonia affecting adults, albeit less frequently, to children. For the purposes of this article we have classified emerging pathogens as follows: True emerging, to pathogens identified for the very first time affecting human population (SARS-CoV-1, SARS-CoV-2, MERS-CoV, avian influenza, and hantavirus); Re-emerging, to known pathogens which circulation was controlled once, but they have reappeared (measles, tuberculosis, antimicrobial resistant bacteria such as CA-MRSA, Mycoplasma pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and new serotypes of post-vaccine pneumococcal); and finally, those that we have called old known with new presentations, including common pathogens that, in particular condition, have changed their form of presentation (rhinovirus, and non-SARS coronavirus). We will review for each of them their epidemiology, forms of presentation, therapy, and prognosis in children compared to the adult with the aim of being able to recognize them to establish appropriate therapy, prognostics, and effective control measures.

Chest imaging of H7N9 subtype of human avian influenza

Background

Human infection with avian influenza A H7N9 virus is an acute respiratory infectious disease, which usually causes severe pneumonia with a high mortality. Chest radiographs and Computed Tomography (CT) are principal radiological modalities to assess the lung abnormalities.

Objectives

The goal of this study was to investigate the chest images characteristic of H7N9 subtype of human avian influenza.

Materials and methods

The clinical and imaging data of 11 cases diagnosed as H7N9 subtype of human avian influenza were collected from 4 cities in the southern region of the Yangtze River, China. The chest imaging manifestations were analyzed by the assigned expert group. The analyzed cases include 7 males and 4 females aged from 20 to 84 years, with a mean of 55.6 years. The clinical symptoms were mainly fever (100%, 11/11) and cough (72.7%, 8/11).

Results

Segmental or lobar ground-glass opacity (GGO) or consolidation was shown in 8 cases (72.7% or 8/11). Air bronchogram was found in 7 cases (63.6% or 7/11). The lesions developed into multiple or diffuse in both lungs rapidly at the progressive stage. The reticulation shadows were shown after some lesions absorbed at the stable stage.

Conclusions

The characteristic imaging demonstrations of H7N9 subtype of human avian influenza are segmental or lobar exudative lesions at lungs at the initial stage, which rapidly progress into bilateral distribution at lungs at the progressive stage.

Association of radiologic findings with mortality in patients with avian influenza H7N9 pneumonia

Background

The novel H7N9 virus causes severe illness, including pneumonia and acute respiratory distress syndrome, with high rates of mortality. We investigated the association of initial radiologic characteristics obtained at admission with clinical outcomes in patients with avian influenza H7N9 pneumonia.

Methods

Demographics, comorbidities, clinical findings, radiologic appearance and scores of the affected lung parenchyma were compared between survivor group (n = 15) and mortality group (n = 7). Two radiologic scores were calculated, one using chest radiography and one using CT. Follow-up CT scans at discharge were analyzed in 12 patients of the survival group.

Results

All the patients in mortality group developed acute respiratory distress syndrome and required mechanical ventilation, while in the survival group 33% (5/15) developed acute respiratory distress syndrome (P<0.05) and 27% (4/15) required mechanical ventilation (P<0.05). The mean radiographic and CT scores of the mortality group were 50% higher compared to the survival group (P<0.05). ROC analysis revealed an area under curve of 0.738 for the radiographic score with an optimal cutoff value of a score of 19 for prediction of mortality, with a sensitivity of 71% and a specificity of 67%, and an area under curve of 0.833 for the CT score with an optimal cutoff value of a CT score of 21 for prediction of mortality, with a sensitivity of 86% and a specificity of 73%. The mean CT score of the affected lung parenchyma at discharge was 30% lower than the initial CT examination (P<0.05).

Conclusion

High initial radiologic score is associated with mortality in patients with avian influenza H7N9 pneumonia.

Association between radiological findings and severity of community-acquired pneumonia in children

Background

There are few published data concerning radiological findings and their relationship with community-acquired pneumonia (CAP) severity. The aim if this study was to assess radiographic findings in children with CAP of different severity in order to evaluate whether some parameters are associated with severe CAP.

Methods

We analysed the characteristics of parenchymal densities in 335 chest radiographs of otherwise healthy children (173 males; mean age ± standard deviation, 7.5 ± 4.5 years) admitted to our Emergency Room for CAP. Upon admission, chest radiographs were obtained in the two standard projections, and the children with severe or mild/moderate CAP were compared in order to identify any correlations between CAP severity and the radiological findings.

Results

Seventy-six of the 335 enrolled children (22.7%) fulfilled the criteria for severe CAP. In comparison with the children with mild/moderate CAP, in severe CAP there was a significantly greater frequency of a bilateral multifocal distribution (p = 0.01), the simultaneous involvement of ≥3 sites (p = 0.007), and the involvement of the right hilum (p = 0.02). The same results were confirmed in the multiple logistic regression model.

Conclusions

This study shows that radiological findings such as a multifocal bilateral distribution, the simultaneous involvement of at least three sites, and right hilar consolidation are associated with severe CAP in otherwise healthy children, and could be considered markers of disease severity in children with CAP.

Peptide targeting and imaging of damaged lung tissue in influenza-infected mice

AIM

In this study, we investigate whether pH (low) insertion peptide (pHLIP) can target regions of lung injury associated with influenza infection.

MATERIALS & METHODS

Fluorophore-conjugated pHLIP was injected intraperitoneally into mice infected with a sublethal dose of H1N1 influenza and visualized histologically.

RESULTS

pHLIP specifically targeted inflamed lung tissues of infected mice in the later stages of disease and at sites where alveolar type I and type II cells were depleted. Regions of pHLIP-targeted lung tissue were devoid of peroxiredoxin 6, the lung-abundant antioxidant enzyme, and were deficient in pneumocytes. Interestingly, a pHLIP variant possessing mutations that render it insensitive to pH changes was also able to target damaged lung tissue.

CONCLUSION

pHLIP holds potential for delivering therapeutics for lung injury during influenza infection. Furthermore, there may be more than one mechanism that enables pHLIP variants to target inflamed lung tissue.

Chest radiographic appearances in adult inpatients admitted with swine flu infection: local experience in Melbourne

INTRODUCTION

The influenza A virus (H1N1) pandemic began in Mexico in March 2009. As of July 2009, there were 5298 reported cases in Australia including 10 deaths. The aim of this review is to demonstrate the local chest radiographic findings in adult inpatients with proven H1N1, to assess the radiological disease progression and resolution, and to evaluate whether the severity of chest X-rays findings had a bearing on the length of admission and need for intensive care admission.

METHODS

Eleven H1N1 patients (5 males and 6 females, mean age of 36), presenting with cough (64%), fever (55%) and shortness of breath (55%), were admitted to our hospital between 13 August and 1 November 2010. Details of radiographic features, risk factors, clinical course including length of stay, doubling time of consolidation and time for 50% resolution of consolidation were recorded and analysed.

RESULTS

Seventy-three per cent of our patients presented with bilateral mid and/or lower zone alveolar consolidation. One patient with underlying cystic fibrosis had only bilateral upper zone consolidation. No pleural effusion, lymphadenopathy or cardiomegaly was noted on any of the plain chest radiographs. The mean doubling time of consolidation was 1.5 days. The mean time for 50% resolution of consolidation after antiviral treatment was 10.5 days. The average length of stay in hospital was 22 days. Ninety-one per cent of our patients required intensive-care unit admission with 50% of those requiring intubation.

CONCLUSION

Rapid progression of bilateral mid and lower zone air-space opacities in relatively young unwell patients, with lack of pleural effusion, pericardial effusion or lymphadenopathy on plain radiographs, should raise the clinical suspicion of H1N1 infection. Patients requiring hospital admission usually show slow clinical and radiological improvement, and require prolonged hospital stays.

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 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.

Chest imaging features of patients afflicted with Influenza A (H1N1) in a Malaysian tertiary referral centre

This is a retrospective descriptive study of the chest imaging findings of 118 patients with confirmed A(H1N1) in a tertiary referral centre. About 42% of the patients had positive initial chest radiographic (CXR) findings. The common findings were bi-basal air-space opacities and perihilar reticular and alveolar infiltrates. In select cases, high-resolution computed tomography (CT) imaging showed ground-glass change with some widespread reticular changes and atelectasis.

Chest radiography findings in adults with pandemic H1N1 2009 influenza

The current pandemic of a novel influenza A (H1N1) virus, commonly referred to as "swine flu", began in Mexico in March 2009 and reached the UK in April 2009. By 21 July 2009, more than 850 suspected cases of influenza had been seen at Birmingham Heartlands Hospital (BHH), including 52 adults with laboratory-confirmed pandemic H1N1 influenza who were admitted. Of seven patients (13%) requiring intensive care, six needed mechanical ventilation, two needed extra-corporeal membrane oxygenation (ECMO) and one died. Of the 52 admitted adults, 42 (81%) had respiratory symptoms or signs and positive PCR tests for novel Influenza A (H1N1) virus. These patients also had chest radiographs (CXR) taken, which were abnormal for 12 patients (29%). Of these, six patients had bilateral consolidation, which was bibasal in three and widespread in three; all six had pleural effusions. A further six patients had unilateral consolidation with predominantly basal changes; one of these patients had a pleural effusion. The odds ratio for requiring intubation and ventilation with H1N1 influenza and an abnormal CXR was 29.0 (95% confidence interval 2.93-287.0). CXR changes were not common in swine flu, but a significant minority of those requiring admission had consolidation on their CXR. Those who required admission and had CXR changes are more likely to require intubation and ventilation than those without abnormalities on CXR.

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

The potential for pulmonary involvement among patients presenting with novel swine-origin influenza A (H1N1) is high. To investigate the utility of chest imaging in this setting, we correlated clinical presentation with chest radiographic and CT findings in patients with proven H1N1 cases. Subjects included all patients presenting with laboratory-confirmed H1N1 between 1 May and 10 September 2009 to one of three urban hospitals. Clinical information was gathered retrospectively, including symptoms, possible risk factors, treatment and hospital survival. Imaging studies were re-read for study purposes, and CXR findings compared with CT scans when available. During the study period, 157 patients presented with subsequently proven H1N1 infection. Hospital admission was necessary for 94 (60%) patients, 16 (10%) were admitted to intensive care and 6 (4%) died. An initial CXR, carried out for 123 (78%) patients, was abnormal in only 40 (33%) cases. Factors associated with increased likelihood for radiographic lung abnormalities were dyspnoea (p<0.001), hypoxaemia (p<0.001) and diabetes mellitus (p = 0.023). Chest CT was performed in 21 patients, and 19 (90%) showed consolidation, ground-glass opacity, nodules or a combination of these findings. 4 of 21 patients had negative CXR and positive CT. Compared with CT, plain CXR was less sensitive in detecting H1N1 pulmonary disease among immunocompromised hosts than in other patients (p = 0.0072). A normal CXR is common among patients presenting to the hospital for H1N1-related symptoms without evidence of respiratory difficulties. The CXR may significantly underestimate lung involvement in the setting of immunosuppression.

Image findings of patients with H1N1 virus pneumonia and acute respiratory failure

RATIONALE AND OBJECTIVES

The aim of this study was to assess the findings of chest radiography and high-resolution computed tomography in patients requiring intensive care unit treatment for severe H1N1 virus pneumonia.

MATERIALS AND METHODS

In 2009, 10 patients required treatment in an intensive care unit for confirmed H1N1 pneumonia. All patients underwent chest radiography and high-resolution computed tomography. All 10 patients required mechanical ventilation because of respiratory failure. Nine patients presented with severe acute respiratory distress syndrome, and one patient died. Four patients underwent extracorporeal membrane oxygenation (ECMO) therapy. The results of chest radiography and high-resolution computed tomographic scans of these patients were systematically analyzed.

RESULTS

The mean age of all patients was 44.1 +/- 12.3 years. All 10 patients showed abnormal results on chest radiography. The radiographic abnormalities were bilateral and multifocal in 10 patients. The predominant radiographic findings were consolidations (n = 9), ground-glass opacities (n = 8), and reticular opacities (n = 2). The most frequent computed tomographic findings at presentation consisted of bilateral ground-glass opacities (n = 9), pleural effusion (n = 9), areas of consolidation (n = 8), interstitial marking (n = 8), and crazy paving (n = 4). All patients undergoing ECMO therapy showed extensive bilateral ground-glass opacities, multifocal areas of consolidation, and crazy paving. Pleural effusion was present in three of four patients undergoing ECMO therapy.

CONCLUSION

Patients requiring treatment in an intensive care unit for severe H1N1 pneumonia are at high risk for developing acute respiratory distress syndrome and frequently require ECMO therapy.

Clinical course of avian influenza A(H5N1) in patients at the Persahabatan Hospital, Jakarta, Indonesia, 2005-2008

Background

Limited understanding of the presentation and course of influenza A(H5N1) infection in humans hinders evidence-based management.

Methods

We reviewed the case records of patients admitted to the Persahabatan Hospital (RSP), Jakarta, Indonesia, with influenza A(H5N1) confirmed by real-time polymerase chain reaction.

Results

Twenty-two previously well patients, aged 3 to 47 years (median 24.5 years), were identified. All attended a clinic or hospital after a median of 2 days of illness (range 0–7). Times to first dose of oseltamivir (three died before receiving oseltamivir) were 2 to 12 days (median 7 days), administered mostly (n = 15) at RSP. Nineteen patients required mechanical ventilation. Deaths numbered 18 (case fatality = 82%) occurring within hours to 6 days of RSP admission, corresponding to 6 to 16 days of illness. Admission hyperglycemia (≥ 140 mg/dL), unrelated to steroids or known underlying diabetes mellitus, and elevated D-dimer levels (0.81–5.2 mg/L, upper limit of normal < 0.5 mg/L) were present in 14/21 (67%) and 20/21 (95%) patients, respectively. Fibrinogen concentrations were mostly low/normal at 129.9 to 517.9 mg/dL (median 241.1, normal 200–400 mg/dL), whereas C-reactive protein (9/11) and ferritin (6/8) levels were increased. Risk factors for death (univariate analysis) included: (1) increased D-dimers, (2) hyperglycema, (3) increased urea, (4) more extensive chest radiograph shadowing, and (5) lower admission oxygen saturation.

Conclusions

Early diagnosis and effective treatment of human influenza A(H5N1) infection remains challenging. Most patients were referred late with advanced disease. Oseltamivir had limited clinical impact. Elevated D-dimer levels, consistent with fibrinolysis, and hyperglycemia warrant more research to determine their underlying mechanisms and optimal treatment.

Thoracic CT findings of novel influenza A (H1N1) infection in immunocompromised patients

The goal of this study is to describe the spectrum of initial and follow-up CT findings of novel influenza A (H1N1) infection in a series of immunocompromised patients. Eight immunocompromised patients with documented novel influenza A (H1N1) had CT imaging at our institution between May 2009 and August 2009. A total of 20 CTs (initial and follow-up) were reviewed for the presence, severity, and distribution of the following: ground glass opacity, consolidation, interlobular septal thickening, mosaic perfusion, airway wall thickening, airway dilatation, nodules, cysts, pleural effusion, pericardial effusion, lymphadenopathy, and air trapping. The most common findings were airway thickening/dilatation, peribronchial ground glass opacity, centrilobular nodules, and tree-in-bud opacities. Peripheral consolidation involving the lower lobes was also a common pattern. Findings frequently involved all lobes and were closely associated with either large or small airways. Two patients presented with atypical CT findings including focal lobar consolidation and patchy lower lobe consolidation with soft tissue centrilobular nodules. Most survivors showed near complete resolution of findings within 35 days. CT scans in immunocompromised patients with novel influenza H1N1 commonly show a strong airway predominance of findings or peripheral areas of consolidation involving the lower lobes. A subset of patients with novel influenza A (H1N1) will show findings not typical of viral infection.

Avian influenza--a review for doctors in travel medicine

First identified in humans in Hong Kong, influenza A/H5N1, known commonly as avian influenza, has caused human disease in 15 countries around the world. Although the current number of confirmed patients is tiny compared to seasonal and the recently emerged H1N1 'swine' influenza, H5N1 remains a candidate for the next highly pathogenic influenza pandemic. Currently, H5N1 has very limited ability to spread from person-to-person but this may change because of mutation or reassortment with other influenza viruses leading to an influenza pandemic with high mortality. If this occurs travellers are likely to be affected and travel medicine doctors will need to consider avian influenza in returning febrile travellers. The early clinical features may be dismissed easily as 'the flu' resulting in delayed treatment. Treatment options are limited. Oral oseltamivir alone has been the most commonly used drug but mortality remains substantial, up to 80% in Indonesia. Intravenous peramivir has been filed for registration and IV zanamivir is being developed. This review will focus on the epidemiological and clinical features of influenza A/H5N1 avian influenza and will highlight aspects relevant to travel medicine doctors.

Manifestações da infecção pelo novo vírus influenza A (H1N1) na tomografia computadorizada de tórax

OBJETIVO: Descrever as alterações na tomografia computadorizada de tórax de casos comprovados de infecção pelo novo vírus influenza A (H1N1). MATERIAIS E MÉTODOS: Três observadores avaliaram, em consenso, nove tomografias computadorizadas de pacientes com infecção pelo vírus influenza A (H1N1) comprovada laboratorialmente. A idade dos pacientes variou de 14 a 64 anos (média de 40 anos), sendo cinco do sexo masculino e quatro do sexo feminino. Quatro pacientes eram previamente hígidos, quatro eram transplantados renais e uma era gestante à época do diagnóstico. Foram avaliadas a presença, a extensão e a distribuição de: a) opacidades em vidro fosco; b) nódulos centrolobulares; c) consolidações; d) espessamento de septos interlobulares; e) derrame pleural; f) linfonodomegalias. RESULTADOS: As alterações mais frequentemente encontradas foram opacidades em vidro fosco, nódulos centrolobulares e consolidações, presentes em nove (100%), cinco (55%) e quatro (44%) dos casos, respectivamente. Derrames pleurais e linfonodomegalias foram menos comuns, ocorrendo em apenas dois (22%) dos casos estudados. CONCLUSÃO: Os achados mais comuns nos casos de infecção pelo novo vírus influenza A (H1N1) foram opacidades em vidro fosco, nódulos centrolobulares e consolidações. Estas alterações não são típicas ou únicas a este agente, podendo ocorrer também em outras infecções virais ou bacterianas.

Pulmonary fibrosis induced by H5N1 viral infection in mice

Background

Inflammatory process results in lung injury that may lead to pulmonary fibrosis (PF). Here, we described PF in mice infected with H5N1 virus.

Methods

Eight-week-old BALB/c mice were inoculated intranasally with 1 × 10¹ MID₅₀ of A/Chicken/Hebei/108/2002(H5N1) viruses. Lung injury/fibrosis was evaluated by observation of hydroxyproline concentrations, lung indexes, and histopathology on days 7, 14, and 30 postinoculation.

Results

H5N1-inoculated mice presented two stages of pulmonary disease over a 30-d period after infection. At acute stage, infected-mice showed typical diffuse pneumonia with inflammatory cellular infiltration, alveolar and interstitial edema and hemorrhage on day 7 postinoculation. At restoration stage, most infected-mice developed PF of different severities on day 30 postinoculation, and 18% of the survived mice underwent severe interstitial and intra-alveolar fibrosis with thickened alveolar walls, collapsed alveoli and large fibrotic areas. The dramatically elevated hydroxyproline levels in H5N1-infected mice showed deposition of collagen in lungs, and confirmed fibrosis of lungs. The dry lung-to-body weight ratio was significantly increased in infected group, which might be associated with the formation of PF in H5N1-infected mice.

Conclusion

Our findings show that H5N1-infected mice develop the typical PF during restoration period, which will contribute to the investigation of fibrogenesis and potential therapeutic intervention in human H5N1 disease.

Clinical features of human influenza A (H5N1) infection in Vietnam: 2004-2006

BACKGROUND

The first cases of avian influenza A (H5N1) in humans in Vietnam were detected in early 2004, and Vietnam has reported the second highest number of cases globally.

METHODS

We obtained retrospective clinical data through review of medical records for laboratory confirmed cases of influenza A (H5N1) infection diagnosed in Vietnam from January 2004 through December 2006. Standard data was abstracted regarding clinical and laboratory features, treatment, and outcome.

RESULTS

Data were obtained for 67 (72%) of 93 cases diagnosed in Vietnam over the study period. Patients presented to the hospital after a median duration of illness of 6 days with fever (75%), cough (89%), and dyspnea (81%). Diarrhea and mucosal bleeding at presentation were more common in fatal than in nonfatal cases. Common findings were bilateral pulmonary infiltrates on chest radiograph (72%), lymphopenia (73%), and increased serum transaminase levels (aspartate aminotransferase, 69%; alanine aminotransferase, 61%). Twenty-six patients died (case fatality rate, 39%; 95% confidence interval, 27%-51%) and the most reliable predictor of a fatal outcome was the presence of both neutropenia and raised alanine aminotransferase level at admission, which correctly predicted 91% of deaths and 82% of survivals. The risk of death was higher among persons aged < or =16 years, compared with older persons (P < .001), and the risk of death was higher among patients who did not receive oseltamivir treatment (P = .048). The benefit of oseltamivir treatment remained after controlling for potential confounding by 1 measure of severity (odds ratio, 0.15; 95% confidence interval, 0.026-0.893; P = .034).

CONCLUSION

In cases of infection with Influenza A (H5N1), the presence of both neutropenia and raised serum transaminase levels predicts a poor outcome. Oseltamivir treatment shows benefit, but treatment with corticosteroids is associated with an increased risk of death.

Chest CT findings of influenza virus-associated pneumonia in 12 adult patients

Objective  In this study, we describe the chest computed tomography findings of influenza virus‐associated pneumonia in adult patients.

Methods  Our retrospective study included 12 adult patients who had proven influenza virus ‐ associated pneumonia.

Results  Out of 12 patients, six were diagnosed as having pure influenza virus pneumonia, five as having bronchopneumonia caused by bacteria associated with influenza A infection, and one as having a cryptogenic organizing pneumonia associated with influenza A infection.

Conclusion  Radiographic findings of influenza virus pneumonia in adult patients consist of ground‐glass attenuation. Localized patchy consolidations were observed in cases of bronchopneumonia.

Intensive care management of life-threatening avian influenza A (H5N1)

A large proportion of patients with avian influenza A (H5N1) develop life-threatening manifestations, often including ARDS, acute renal failure and multiple organ failure that requires aggressive intensive care management. The pace of development of respiratory failure is often rapid and can occur in previously healthy hosts, mandating close observation and timely intervention of infected individuals. Use of standard, contact, droplet and airborne isolation precautions is recommended to protect healthcare workers. Key components of ARDS management encompass appropriate mechanical ventilation including limiting tidal volume to </=6 mL/kg of predicted body weight, maintaining transpulmonary pressures </=30 cm H(2)O, and utilizing positive end-expiratory pressure to limit alveolar deflation and to improve oxygenation. Additional strategies include conservative fluid management and using nutrition supplemented with antioxidants. Use of corticosteroids is controversial for both early and late ARDS and although often used for avian influenza, beneficial effects on outcomes have not been demonstrated for corticosteroids. Prone positioning can improve oxygenation temporarily and might be useful as rescue therapy for severe hypoxemia. Administration of inhaled nitric oxide and high frequency oscillatory ventilation can improve oxygenation but have not been demonstrated to improve survival in ARDS-their role in avian influenza is uncertain and availability limited. Management of multiple organ failure may include vasopressor support for septic shock and renal replacement therapy for acute renal failure.

Review of clinical symptoms and spectrum in humans with influenza A/H5N1 infection

Influenza A/H5N1 infection has become the major emerging infectious disease of global concern again since late 2003. A history of exposure to dead or sick poultry or wild birds occurs in over 60% of cases of human H5N1 infection. The incubation period of avian-to-human transmission is generally between 2 and 5 days and the median duration of symptoms before hospitalization is about 4.5 days. The clinical spectrum has ranged from asymptomatic infection or mild influenza-like illness to severe pneumonia and multi-organ failure. Fever > 38 degrees C, cough and dyspnoea are the major symptoms on presentation, whereas gastrointestinal symptoms such as watery diarrhoea, vomiting and abdominal pain are common early in the course of the disease. In contrast, upper respiratory tract symptoms are less prominent in human H5N1 infection when compared to seasonal influenza. Laboratory features of human H5N1 infection include leucopoenia, especially lymphopenia, elevated amino-transaminases, thrombocytopenia, prolonged prothrombin time and activated partial thromboplastin time, increased D-Dimer, increased serum lactate dehydrogenase and creatinine phospho-kinase, and hypoalbuminemia. A low absolute lymphocyte count on admission is associated with more severe disease and death. Radiographic abnormalities include multi-focal airspace consolidation, interstitial infiltrates, patchy or lobar involvement, with rapid progression to bilateral and diffuse ground-glass opacities consistent with ARDS. However, none of the clinical, laboratory and radiographic features are specific to H5N1 infection. A detailed exposure history needs to be elicited, including any close contact with sick or dead poultry, wild birds, other severely ill persons, travel to an area with A/H5N1 activity or work in laboratory handling samples possibly containing A/H5N1 virus.