Clinical review: primary influenza viral pneumonia

TGF-β-induced IL-6 prevents development of acute lung injury in influenza A virus-infected F508del CFTR-heterozygous mice

As the eighth leading cause of annual mortality in the USA, influenza A viruses are a major public health concern. In 20% of patients, severe influenza progresses to acute lung injury (ALI). However, pathophysiological mechanisms underlying ALI development are poorly defined. We reported that, unlike wild-type (WT) C57BL/6 controls, influenza A virus-infected mice that are heterozygous for the F508del mutation in the cystic fibrosis transmembrane conductance regulator (HETs) did not develop ALI. This effect was associated with higher IL-6 and alveolar macrophages (AMs) at 6 days postinfection (d.p.i.) in HET bronchoalveolar lavage fluid (BALF). In the present study, we found that HET AMs were an important source of IL-6 at 6 d.p.i. Infection also induced TGF-β production by HET but not WT mice at 2 d.p.i. TGF-β neutralization at 2 d.p.i. (TGF-N) significantly reduced BALF IL-6 in HETs at 6 d.p.i. Neither TGF-N nor IL-6 neutralization at 4 d.p.i. (IL-6-N) altered postinfection weight loss or viral replication in either mouse strain. However, both treatments increased influenza A virus-induced hypoxemia, pulmonary edema, and lung dysfunction in HETs to WT levels at 6 d.p.i. TGF-N and IL-6-N did not affect BALF AM and neutrophil numbers but attenuated the CXCL-1/keratinocyte chemokine response in both strains and reduced IFN-γ production in WT mice. Finally, bone marrow transfer experiments showed that HET stromal and myeloid cells are both required for protection from ALI in HETs. These findings indicate that TGF-β-dependent production of IL-6 by AMs later in infection prevents ALI development in influenza A virus-infected HET mice.

Pandemic influenza A (H1N1) infection in pregnant and nonpregnant women in Spain (2009-2010)

The present study aimed to compare the main features of infection with pandemic influenza A virus in pregnant and nonpregnant women admitted to hospitals in Spain during the first waves of the 2009-2010 influenza pandemic. This was a prospective (November 2009 to June 2010), multicenter observational study. All cases were women of reproductive age who had not been vaccinated against seasonal or pandemic influenza A. Influenza infection was confirmed by reverse transcription-polymerase chain reaction (RT-PCR). The sociodemographic and clinical data of all cases were reviewed. A total of 219 inpatients, including 49 pregnant women and 170 nonpregnant women, were enrolled in the study upon admission to participating hospitals. The most substantially different symptoms between the groups were respiratory distress and unilobar consolidation, both of which were more frequent among nonpregnant women. Antibiotics and systemic corticosteroids were more frequently used in nonpregnant women; however, there were no differences in the rates of treatment with antivirals. Our findings indicated that the compared with nonpregnant women, pregnant women in this study did not have significantly different symptoms and were not at increased risk of complications from pandemic influenza virus infection.

An infectious disease/fever screening radar system which stratifies higher-risk patients within ten seconds using a neural network and the fuzzy grouping method

Objectives

To classify higher-risk influenza patients within 10 s, we developed an infectious disease and fever screening radar system.

Methods

The system screens infected patients based on vital signs, i.e., respiration rate measured by a radar, heart rate by a finger-tip photo-reflector, and facial temperature by a thermography. The system segregates subjects into higher-risk influenza (HR-I) group, lower-risk influenza (LR-I) group, and non-influenza (Non-I) group using a neural network and fuzzy clustering method (FCM). We conducted influenza screening for 35 seasonal influenza patients and 48 normal control subjects at the Japan Self-Defense Force Central Hospital. Pulse oximetry oxygen saturation (SpO₂) was measured as a reference.

Results

The system classified 17 subjects into HR-I group, 26 into LR-I group, and 40 into Non-I group. Ten out of the 17 HR-I subjects indicated SpO₂ <96%, whereas only two out of the 26 LR-I subjects showed SpO₂ <96%. The chi-squared test revealed a significant difference in the ratio of subjects showed SpO₂ <96% between HR-I and LR-I group (p < 0.001). There were zero and nine normal control subjects in HR-I and LR-I groups, respectively, and there was one influenza patient in Non-I group.

Conclusions

The combination of neural network and FCM achieved efficient detection of higher-risk influenza patients who indicated SpO₂ 96% within 10 s.

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A novel infectious disease/fever screening radar system stratifies higher-risk patients within ten seconds.

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Use of an optimal neural network and the fuzzy clustering method to classify multiple-dimensional vital signs data.

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The system can be used for preventing secondary exposure of physicians during outbreaks of infectious disease.

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The system has potential to serve as a helpful tool for rapid mass screening of infectious disease.

Antiviral natural products and herbal medicines

Viral infections play an important role in human diseases, and recent outbreaks in the advent of globalization and ease of travel have underscored their prevention as a critical issue in safeguarding public health. Despite the progress made in immunization and drug development, many viruses lack preventive vaccines and efficient antiviral therapies, which are often beset by the generation of viral escape mutants. Thus, identifying novel antiviral drugs is of critical importance and natural products are an excellent source for such discoveries. In this mini-review, we summarize the antiviral effects reported for several natural products and herbal medicines.

Influenza A (H1N1) vs non-H1N1 ARDS: analysis of clinical course

PURPOSE

The purpose of the study is to compare H1N1-induced acute respiratory distress syndrome (ARDS) with ARDS due to other causes of severe community-acquired pneumonia focusing on pulmonary function.

MATERIALS AND METHODS

This is a retrospective data analysis of adult ARDS patients between January 2009 and December 2010 in an ARDS referral center. Patient characteristics, severity of illness scores, modalities, and duration of extracorporeal lung support were evaluated as well as intensive care unit stay and survival. Parameters of mechanical ventilation and pulmonary function were analyzed on day of admission and over the consecutive 10 days using a nonparametric analysis of longitudinal data in a 2-factorial design. In a logistic regression analysis, risk factors for extracorporeal lung support were investigated.

RESULTS

Twenty-one patients with H1N1-ARDS and 41 with non-H1N1-ARDS were identified. Gas exchange was more severely impaired in patients with H1N1-ARDS over course of time. Extracorporeal membrane oxygenation was more frequently needed in H1N1-ARDS. Despite significantly prolonged weaning off extracorporeal lung support and intensive care unit stay in H1N1 patients, the proportion of survivors did not differ significantly. Only Sepsis-Related Organ Failure Assessment score could be identified as an independent predictor of extracorporeal lung support.

CONCLUSIONS

Clinical course of H1N1-ARDS is substantially different from non-H1N1-ARDS. Affected patients may require extensive therapy including extracorporeal lung support in ARDS referral centers.

The high burden of pneumonia on US emergency departments during the 2009 influenza pandemic

OBJECTIVES

During the 2009 influenza A (H1N1) pandemic, unusual influenza activity outside the typical winter season provided a unique opportunity to evaluate the association between influenza and pneumonia incidence. We sought to quantify the impact of the 2009 pandemic on the incidence of emergency department (ED) visits for pneumonia in the United States (US).

METHODS

Using the Nationwide Emergency Department Survey, we estimated monthly counts and rates of excess all-cause pneumonia ED visits in the US attributable to the pandemic by comparing observed pneumonia ED visits during the pandemic (April 2009-March 2010) to expected values modeled from the three prior years.

RESULTS

The pandemic was associated with an excess of 180,560 pneumonia ED visits or 0.59 excess pneumonia visits per 1000 US population (95% confidence interval: 0.55, 0.62). These excess visits accounted for 7.0% of all pneumonia ED visits during the pandemic year. The greatest excess occurred during months with highest influenza activity (September-November 2009). Persons aged <65 years accounted for 94% of the excess pneumonia visits.

CONCLUSIONS

ED visits for pneumonia increased substantially during the 2009 pandemic, especially during peak influenza activity, suggesting a strong association between influenza activity and pneumonia incidence during the pandemic period.

Differential host response, rather than early viral replication efficiency, correlates with pathogenicity caused by influenza viruses

Influenza viruses exhibit large, strain-dependent differences in pathogenicity in mammalian hosts. Although the characteristics of severe disease, including uncontrolled viral replication, infection of the lower airway, and highly inflammatory cytokine responses have been extensively documented, the specific virulence mechanisms that distinguish highly pathogenic strains remain elusive. In this study, we focused on the early events in influenza infection, measuring the growth rate of three strains of varying pathogenicity in the mouse airway epithelium and simultaneously examining the global host transcriptional response over the first 24 hours. Although all strains replicated equally rapidly over the first viral life-cycle, their growth rates in both lung and tracheal tissue strongly diverged at later times, resulting in nearly 10-fold differences in viral load by 24 hours following infection. We identified separate networks of genes in both the lung and tracheal tissues whose rapid up-regulation at early time points by specific strains correlated with a reduced viral replication rate of those strains. The set of early-induced genes in the lung that led to viral growth restriction is enriched for both NF-κB binding site motifs and members of the TREM1 and IL-17 signaling pathways, suggesting that rapid, NF-κB –mediated activation of these pathways may contribute to control of viral replication. Because influenza infection extending into the lung generally results in severe disease, early activation of these pathways may be one factor distinguishing high- and low-pathogenicity strains.

Laninamivir octanoate and artificial surfactant combination therapy significantly increases survival of mice infected with lethal influenza H1N1 Virus

Background

Patients with influenza virus infection can develop severe pneumonia and acute respiratory distress syndrome (ARDS) which have a high mortality. Influenza virus infection is treated worldwide mainly by neuraminidase inhibitors (NAIs). However, monotherapy with NAIs is insufficient for severe pneumonia secondary to influenza virus infection. We previously demonstrated that mice infected with a lethal dose of influenza virus develop diffuse alveolar damage (DAD) with alveolar collapse similar to that seen in ARDS in humans. Additionally, pulmonary surfactant proteins were gradually increased in mouse serum, suggesting a decrease in pulmonary surfactant in the lung. Therefore, the present study examined whether combination therapy of NAI with exogenous artificial surfactant affects mortality of influenza virus-infected mice.

Methodology/Principal Findings

BALB/c mice were inoculated with several viral doses of influenza A/Puerto Rico/8/34 (PR8) virus (H1N1). The mice were additionally administered exogenous artificial surfactant in the presence or absence of a new NAI, laninamivir octanoate. Mouse survival, body weight and general condition were observed for up to 20 days after inoculation. Viral titer and cytokine/chemokine levels in the lungs, lung weight, pathological analysis, and blood O₂ and CO₂ pressures were evaluated. Infected mice treated with combination therapy of laninamivir octanoate with artificial surfactant showed a significantly higher survival rate compared with those that received laninamivir octanoate monotherapy (p = 0.003). However, virus titer, lung weight and cytokine/chemokine responses were not different between the groups. Histopathological examination, a hydrostatic lung test and blood gas analysis showed positive results in the combination therapy group.

Conclusions/Significance

Combination therapy of laninamivir octanoate with artificial surfactant reduces lethality in mice infected with influenza virus, and eventually suppresses DAD formation and preserves lung function. This combination could be effective for prevention of severe pneumonia secondary to influenza virus infection in humans, which is not improved by NAI monotherapy.

Clinical significance of pleural effusion in the new influenza A (H1N1) viral pneumonia in children and adolescent

BACKGROUND

Parapneumonic effusion has been reported to develop either in typical bacterial infection or in viral pneumonia with bacterial co-infection and to cause death. Swine-origin influenza A (H1N1) virus infection can be accompanied with pleural effusion; however, there are no reports about the significance of pleural effusion in H1N1 pneumonia. We retrospectively analyzed both the clinical characteristics and the significance of pleural effusion associated with H1N1 pneumonia in children and adolescent.

METHOD

Eighty-nine patients who were admitted with H1N1 pneumonia were divided into two groups: 17 patients with pleural effusion (i.e., the effusion group), and 72 patients without pleural effusion (the non-effusion group).

RESULTS

Lymphopenia (P = 0.030), elevation of the C-reactive protein (P = 0.026), and positive rate of anti-sptreptolysin O titer (P = 0.040) were significantly increased in the effusion group than in the non-effusion group. In addition, the need for treatment with both oxygen (P < 0.001) and oseltamivir (P = 0.013) was significantly increased in the effusion group. However, there was no significant difference between the two investigated groups in the duration of the treatment with intravenous antibiotics, the time of fever remission calculated from admission, and the days of hospital stay. Also, there was no documented bacterial co-infection in any of the studied groups.

CONCLUSION

This result suggested that pleural effusion in H1N1 pneumonia could develop without bacterial co-infection and had mild clinical course.

Pneumonia part 3: management and prevention of influenza virus

This is the third and final article in a series looking at the morbidity and mortality associated with community-acquired pneumonia (CAP). It will discuss the epidemiology of influenza and the part that it plays in this important disease, and will also look at preventive strategies.

In vivo platelet activation in critically ill patients with primary 2009 influenza A(H1N1)

BACKGROUND

Changes in platelet reactivity during 2009 influenza A(H1N1) (A[H1N1]) have not been characterized.

METHODS

We prospectively examined platelet activation and cytokine responses in patients with A(H1N1) (n = 20), matched patients with bacterial pneumonia (n = 15), and nonhospitalized, healthy control subjects (n = 10).

RESULTS

Platelet-monocyte aggregation was higher in patients with A(H1N1) (21.4% ± 4.7%) compared with patients with pneumonia (10.9% ± 3.7%) and control subjects (8.1% ± 4.5%, P < .05). Similarly, PAC-1 (antibody that binds to the active conformation of integrin α(IIb)β(3)) binding to platelets is increased in patients with A(H1N1) (9.5% ± 4.7%) compared with patients with pneumonia (1.0% ± 0.7%) and healthy subjects (0.61% ± 0.15%, P < .10). PAC-1 binding was twofold higher in patients with A(H1N1) with shock vs those without shock. IL-6 levels were elevated in patients with A(H1N1), indicating systemic inflammation consistent with activation of circulating platelets.

CONCLUSIONS

These findings, derived from a small but documented cohort of patients, demonstrate that platelet activation responses during A(H1N1) are enhanced-exceeding responses in patients with bacterial pneumonia-and provide new evidence that platelets may contribute to inflammatory responses during A(H1N1).

Critically ill children with pandemic influenza (H1N1) in pediatric intensive care units in Turkey

OBJECTIVES

To outline the epidemiologic features, clinical presentation, clinical courses, and outcomes in critically ill children with pandemic influenza in pediatric intensive care units.

DESIGN

Retrospective, observational, multicenter study.

SETTING

Thirteen tertiary pediatric intensive care units in Turkey.

PATIENTS

Eighty-three children with confirmed infection attributable to pandemic influenza detected by reverse-transcriptase polymerase chain reaction assay between November 1 and December 31, 2009 who were admitted to critical care units.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

During a 2-month period, 532 children were hospitalized with pandemic influenza and 83 (15.6%) needed critical care. For the 83 patients requiring critical care, the median age was 42 (range, 2-204) months, with 24 (28.9%) and 48 (57.8%) of patients younger than 2 and 5 yrs, respectively. Twenty (24.1%) patients had no underlying illness, but 63 (75.9%) children had an underlying chronic illness. Indications for admission to the pediatric intensive care unit were respiratory failure in 66 (79.5%), neurologic deterioration in six (7.2%), and gastrointestinal symptoms in five (6.0%) patients. Acute lung injury was diagnosed in 23 (27.7%), acute respiratory distress syndrome was diagnosed in 34 (41%), and 51 (61.4%) patients were mechanically ventilated. Oseltamivir was used in 80 (96%) patients. The mortality rate for children with pandemic influenza 2009 was 30.1% compared to an overall mortality rate of 13.7% (p = .0016) among pediatric intensive care unit patients without pandemic influenza during the study period. Also, the mortality rate was 31.7% in patients with comorbidities and 25.0% in previously healthy children (p = .567). The cause of death was primary pandemic influenza infection in 16 (64%), nosocomial infection in four (16%), and primary disease progression in five (20%) patients. The odds ratio for respiratory failure was 14.7 (95% confidence interval, 1.85-111.11), and odds ratio for mechanical ventilation was 27.7 (95% confidence interval, 0.003-200).

CONCLUSIONS

Severe disease and high mortality rates were seen in children with pandemic influenza. Death attributable to pandemic influenza occurred in all age groups of children with or without underlying illness. Multiple organ dysfunction syndrome is associated with increased mortality, and death is frequently secondary to severe lung infection caused by pandemic influenza.

Severe pandemic (H1N1)v influenza A infection: report on the first deaths in Spain

BACKGROUND AND OBJECTIVE

The impact of pandemic influenza A (H1N1)v infection is still unknown but it is associated with a high case-fatality rate.

METHODS

This was a prospective, observational, multicentre study conducted in 144 Spanish intensive care units. Demographic and clinical data were reviewed for all cases of pandemic influenza A (H1N1)v infection reported from 23 June 2009 through 11 February 2010 and confirmed by reverse transcriptase PCR assay.

RESULTS

Out of 872 cases reported by statewide surveillance, data for the first 131 deceased patients were analysed. Thirty-seven patients (28.2%) died within the first 14 days. The median age of these patients was 46 years (interquartile range 35-58) and 60.3% were male. Twenty-eight patients (21.4%) did not present with any comorbidities on admission. Forty-six per cent of patients were reported to be obese and 22 (16.8%) had COPD. The vast majority of the patients (72.5%) had viral pneumonia; 95.4% of these had bilateral patchy alveolar opacities (predominantly basal), affecting three or four quadrants. One hundred and fifteen patients (87.8%) developed multi-organ dysfunction syndrome. Ninety-seven patients (74%) required vasopressor drugs, 37 (27.2%) received renal replacement therapy, and 47 (35.1%) received intravenous corticosteroids on admission to the intensive care unit. Only 68 patients (51.9%) received empirical antiviral treatment.

CONCLUSIONS

One-third of patients with pandemic influenza A (H1N1)v infection died within the first two weeks and these were young patients, with rapidly progressive viral pneumonia as the primary cause of admission. Obese patients were at high risk but one in four patients did not present with any risk factors on admission. Only half the patients received empirical antiviral therapy and this was administered late.

Risk factors of A/H1N1 etiology in pneumonia and its impact on mortality

OBJECTIVE

Pandemic flu has changed the epidemiology of pneumonia, thus challenging the prediction of etiology and outcome. We analyze the risk factors to predict influenza A/H1N1 infection in patients with pneumonia, and the impact of this etiology on mortality during a pandemic period. Differences between pneumonia with or without A/H1N1 coinfection are described.

METHODS

Retrospective observational study in 364 consecutive patients hospitalized with pneumonia during the A/H1N1 pandemic flu, April-December 2009.

RESULTS

294 patients (80.5%) had A/H1N1(-) pneumonia, 47 (13.2%) A/H1N1(+) pneumonia, and 23 (6.3%) coinfection. Mortality during hospitalization was 24/294 (8.2%), 8/47 (16.7%), 2/23 (8.7%) respectively. A regression logistic analysis (Area under curve, AUC 0.81) to predict A/H1N1(+) pneumonia identified four independent variables: age < 60 years (Odds ratio, OR 5.9), multilobar infiltrates (OR 7.7), C-reactive protein (CRP) < 10 mg/dL (OR 2.8), and leukopenia < 5000/mm(3) (OR 3.4). Risk factors for in-hospital mortality in the whole group were A/H1N1 (+) etiology and LDH > 600 IU/L (OR 4.1) when adjusting for PSI, and hypoxemia (OR 4.2) when adjusting for CURB 65 (AUC 0.81). Heart disease (OR 27.4) and LDH > 600 IU/L (OR 10.5) were risk factors for in-hospital mortality in A/H1N1(+) patients (AUC 0.81)

CONCLUSION

Leukopenia, multilobar infiltrates, CRP<10 mg/dl and age < 60 years were independently associated with A/H1N1(+) etiology. Pandemic A/H1N1(+) increased mortality pneumonia. Heart disease and LDH > 600 were independently associated with mortality in A/H1N1(+) pneumonia.

Clinical aspects and cytokine response in severe H1N1 influenza A virus infection

Introduction

The immune responses in patients with novel A(H1N1) virus infection (nvA(H1N1)) are incompletely characterized. We investigated the profile of Th1 and Th17 mediators and interferon-inducible protein-10 (IP-10) in groups with severe and mild nvA(H1N1) disease and correlated them with clinical aspects.

Methods

Thirty-two patients hospitalized with confirmed nvA(H1N1) infection were enrolled in the study: 21 patients with nvA(H1N1)-acute respiratory distress syndrome (ARDS) and 11 patients with mild disease. One group of 20 patients with bacterial sepsis-ARDS and another group of 15 healthy volunteers were added to compare their cytokine levels with pandemic influenza groups. In the nvA(H1N1)-ARDS group, the serum cytokine samples were obtained on admission and 3 days later. The clinical aspects were recorded prospectively.

Results

In the nvA(H1N1)-ARDS group, obesity and lymphocytopenia were more common and IP-10, interleukin (IL)-12, IL-15, tumor necrosis factor (TNF)α, IL-6, IL-8 and IL-9 were significantly increased versus control. When comparing mild with severe nvA(H1N1) groups, IL-6, IL-8, IL-15 and TNFα were significantly higher in the severe group. In nonsurvivors versus survivors, IL-6 and IL-15 were increased on admission and remained higher 3 days later. A positive correlation of IL-6, IL-8 and IL-15 levels with C-reactive protein and with > 5-day interval between symptom onset and admission, and a negative correlation with the PaO₂:FiO₂ ratio, were found in nvA(H1N1) groups. In obese patients with influenza disease, a significant increased level of IL-8 was found. When comparing viral ARDS with bacterial ARDS, the level of IL-8, IL-17 and TNFα was significantly higher in bacterial ARDS and IL-12 was increased only in viral ARDS.

Conclusions

In our critically ill patients with novel influenza A(H1N1) virus infection, the hallmarks of the severity of disease were IL-6, IL-15, IL-8 and TNFα. These cytokines, except TNFα, had a positive correlation with the admission delay and C-reactive protein, and a negative correlation with the PaO₂:FiO₂ ratio. Obese patients with nvA(H1N1) disease have a significant level of IL-8. There are significant differences in the level of cytokines when comparing viral ARDS with bacterial ARDS.

Year in review 2009: Critical Care--infection

In 2009 Critical Care provided important and clinically relevant research data for management and prevention of infections in critically ill patients. The present review summarises the results of these observational studies and clinical trials and discusses them in the context of the current relevant scientific and clinical background. In particular, we discuss recent epidemiologic data on nosocomial infections in intensive care units, present new approaches to prevention of ventilator-associated pneumonia, describe recent advances in biomarker-guided antibiotic stewardship and attempt to briefly summarise specific challenges related to the management of infections caused by multidrug-resistant microorganisms and influenza A (H1N1).