Histopathologic and immunohistochemical features of fatal influenza virus infection in children during the 2003-2004 season

Comparative Pathology of Animal Models for Influenza A Virus Infection

Animal models are essential for studying disease pathogenesis and to test the efficacy and safety of new vaccines and therapeutics. For most diseases, there is no single model that can recapitulate all features of the human condition, so it is vital to understand the advantages and disadvantages of each. The purpose of this review is to describe popular comparative animal models, including mice, ferrets, hamsters, and non-human primates (NHPs), that are being used to study clinical and pathological changes caused by influenza A virus infection with the aim to aid in appropriate model selection for disease modeling.

Influenza in Children and Adolescents: Epidemiology, Management, and Prevention

EDUCATION GAP

Influenza is among the most common infectious causes of pediatric emergency department visits and hospitalizations. Clinicians should use evidence-based guidelines to learn how to identify, manage, prevent, and treat influenza cases. Disease caused by influenza virus can be mitigated with appropriate treatment and prevention efforts.

OBJECTIVES After completing this article, readers should be able to:

1. Describe the virology and epidemiology of influenza.

2. List the clinical features and complications of influenza infections.

3. List the benefits and limitations of testing modalities for the diagnosis of influenza.

4. Appropriately apply American Academy of Pediatrics, Infectious Diseases Society of America, and Centers for Disease Control and Prevention (CDC) treatment guidelines for influenza or suspected influenza.

5. Describe the importance of influenza vaccination.

Microorganisms associated with increased risk of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that affects more than 7 million people worldwide. Its aetiology is unknown, although the hypothesis of a genetic susceptibility to environmental agents is accepted. These environmental agents include fungi, bacteria, and viruses. Three microorganisms are directly associated with a significantly increased risk of developing Parkinson's disease: the fungal genus Malassezia, the bacterium Helicobacter pylori, and the hepatitis C virus. If the host is vulnerable due to genetic susceptibility or immune weakness, these microorganisms can access and infect the nervous system, causing chronic neuroinflammation with neurodegeneration. Other microorganisms show an epidemiological association with the disease, including the influenza type A, Japanese encephalitis type B, St Louis, and West Nile viruses. These viruses can affect the nervous system, causing encephalitis, which can result in parkinsonism. This article reviews the role of all these microorganisms in Parkinson's disease.

Influenza-Associated Disseminated Aspergillosis in a 9-Year-Old Girl Requiring ECMO Support

A previously healthy 9-year-old girl developed fulminant myocarditis due to severe influenza A infection complicated with methicillin-resistant Staphylococcus aureus pneumonia, requiring extracorporeal membrane oxygenation (ECMO) support. Twelve days after admission, Aspergillus fumigatus was isolated in tracheal aspirate, and 12 h later she suddenly developed anisocoria. Computed tomography (CT) of the head showed fungal brain lesions. Urgent decompressive craniectomy with lesion drainage was performed; histopathology found hyphae in surgical samples, culture-positive for Aspergillus fumigatus (susceptible to azoles, echinocandins, and amphotericin B). Extension workup showed disseminated aspergillosis. After multiple surgeries and combined antifungal therapy (isavuconazole plus liposomal amphotericin B), her clinical course was favorable. Isavuconazole therapeutic drug monitoring was performed weekly. Extensive immunological study ruled out primary immunodeficiencies. Fluorine-18 fluorodeoxyglucose positron emission tomography/CT (¹⁸F-FDG PET/CT) follow-up showed a gradual decrease in fungal lesions. Influenza-associated pulmonary aspergillosis is well-recognized in critically ill adult patients, but pediatric data are scant. Clinical features described in adults concur with those of our case. Isavuconazole, an off-label drug in children, was chosen because our patient had severe renal failure. To conclude, influenza-associated pulmonary aspergillosis is uncommon in children admitted to intensive care for severe influenza, but pediatricians should be highly aware of this condition to enable prompt diagnosis and treatment.

Tissue-based SARS-CoV-2 detection in fatal COVID-19 infections: Sustained direct viral-induced damage is not necessary to drive disease progression

Coronavirus disease 2019 (COVID-19) is an ongoing pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although viral infection is known to trigger inflammatory processes contributing to tissue injury and organ failure, it is unclear whether direct viral damage is needed to sustain cellular injury. An understanding of pathogenic mechanisms has been handicapped by the absence of optimized methods to visualize the presence and distribution of SARS-CoV-2 in damaged tissues. We first developed a positive control cell line (Vero E6) to validate SARS-CoV-2 detection assays. We then evaluated multiple organs (lungs, kidneys, heart, liver, brain, intestines, lymph nodes, and spleen) from fourteen COVID-19 autopsy cases using immunohistochemistry (IHC) for the spike and the nucleoprotein proteins, and RNA in situ hybridization (RNA ISH) for the spike protein mRNA. Tissue detection assays were compared with quantitative polymerase chain reaction (qPCR)-based detection. SARS-CoV-2 was histologically detected in the Vero E6 positive cell line control, 1 of 14 (7%) lungs, and none (0%) of the other 59 organs. There was perfect concordance between the IHC and RNA ISH results. qPCR confirmed high viral load in the SARS-CoV-2 ISH-positive lung tissue, and absent or low viral load in all ISH-negative tissues. In patients who die of COVID-19-related organ failure, SARS-CoV-2 is largely not detectable using tissue-based assays. Even in lungs showing widespread injury, SARS-CoV-2 viral RNA or proteins were detected in only a small minority of cases. This observation supports the concept that viral infection is primarily a trigger for multiple-organ pathogenic proinflammatory responses. Direct viral tissue damage is a transient phenomenon that is generally not sustained throughout disease progression.

Microorganisms that are related with increased risk for Parkinson's disease

Parkinson's disease is a neurodegenerative disorder that affects more than 7 million people worldwide. Its aetiology is unknown, although the hypothesis of a genetic susceptibility to environmental agents is accepted. These environmental agents include fungi, bacteria, and viruses. Three microorganisms are directly associated with a significantly increased risk of developing Parkinson's disease: the fungal genus Malassezia, the bacterium Helicobacter pylori, and the hepatitis C virus. If the host is vulnerable due to genetic susceptibility or immune weakness, these microorganisms can access and infect the nervous system, causing chronic neuroinflammation with neurodegeneration. Other microorganisms show an epidemiological association with the disease, including the influenza type A, Japanese encephalitis type B, St Louis, and West Nile viruses. These viruses can affect the nervous system, causing encephalitis, which can result in parkinsonism. This article reviews the role of all these microorganisms in Parkinson's disease.

Immune mechanisms of pulmonary intravascular coagulopathy in COVID-19 pneumonia

The lung pathology seen in patients with coronavirus disease 2019 (COVID-19) shows marked microvascular thrombosis and haemorrhage linked to extensive alveolar and interstitial inflammation that shares features with macrophage activation syndrome (MAS). We have termed the lung-restricted vascular immunopathology associated with COVID-19 as diffuse pulmonary intravascular coagulopathy, which in its early stages is distinct from disseminated intravascular coagulation. Increased circulating D-dimer concentrations (reflecting pulmonary vascular bed thrombosis with fibrinolysis) and elevated cardiac enzyme concentrations (reflecting emergent ventricular stress induced by pulmonary hypertension) in the face of normal fibrinogen and platelet levels are key early features of severe pulmonary intravascular coagulopathy related to COVID-19. Extensive immunothrombosis over a wide pulmonary vascular territory without confirmation of COVID-19 viraemia in early disease best explains the adverse impact of male sex, hypertension, obesity, and diabetes on the prognosis of patients with COVID-19. The immune mechanism underlying diffuse alveolar and pulmonary interstitial inflammation in COVID-19 involves a MAS-like state that triggers extensive immunothrombosis, which might unmask subclinical cardiovascular disease and is distinct from the MAS and disseminated intravascular coagulation that is more familiar to rheumatologists.

Baloxavir Marboxil 2% Granules in Japanese Children With Influenza: An Open-label Phase 3 Study

BACKGROUND

A granule formulation of baloxavir marboxil, a selective inhibitor of influenza cap-dependent endonuclease, was newly developed for children with difficulty swallowing tablets.

METHODS

A multicenter open-label study was conducted during the 2017-2018 influenza season to assess the safety, pharmacokinetics and clinical/virologic outcomes of single, oral, weight-based doses of baloxavir granules in Japanese children infected with influenza virus. The primary clinical endpoint was the time to illness alleviation of influenza.

RESULTS

All 33 enrolled children completed the study and received baloxavir (1 mg/kg for 12 children weighing <10 kg, 10 mg for 21 children weighing 10 to <20 kg). Detected viruses were influenza B (36.4%), A(H1N1)pdm09 (33.3%) and A(H3N2) (27.3%). Adverse events (AEs) were reported in 54.5% of children. No deaths, serious AEs or AEs leading to discontinuation were reported. The mean (SD) plasma concentrations of baloxavir acid at 24 hours post-dose were 72.8 (24.0) and 51.3 (19.3) ng/mL in the 1-mg/kg and 10-mg dose groups, respectively. The median time to illness alleviation (95% confidence interval) was 45.3 (28.5-64.1) hours. A >4-log decrease in infectious viral titer occurred on day 2 and a temporary 2-log increase on day 4. Polymerase acidic protein/I38T/M-substituted viruses were detected in 5 children infected with influenza A, but none with influenza B.

CONCLUSIONS

Baloxavir granules and the weight-based dose regimen were considered to be well tolerated in children, with rapid influenza virus reduction and associated symptom alleviation. Evidence of baloxavir activity against influenza B was observed, but further data are required for confirmation.

Blocking IL-1 to prevent respiratory failure in COVID-19

COVID-19 is an emerging disease that can manifest itself as asymptomatic or mild respiratory tract infection in the majority of individuals, but in some, it can progress into severe pneumonia and acute respiratory distress syndrome (ARDS). Inflammation is known to play a crucial role in the pathogenesis of severe infections and ARDS and evidence is emerging that the IL-1/IL-6 pathway is highly upregulated in patients with severe disease. These findings open new avenues for host-directed therapies in patients with symptomatic SARS-CoV-2 infection and might in addition to antiviral treatment be enough to curb the currently unacceptably high morbidity and mortality associated with COVID-19.

Immune mechanisms of pulmonary intravascular coagulopathy in COVID-19 pneumonia

The lung pathology seen in patients with coronavirus disease 2019 (COVID-19) shows marked microvascular thrombosis and haemorrhage linked to extensive alveolar and interstitial inflammation that shares features with macrophage activation syndrome (MAS). We have termed the lung-restricted vascular immunopathology associated with COVID-19 as diffuse pulmonary intravascular coagulopathy, which in its early stages is distinct from disseminated intravascular coagulation. Increased circulating D-dimer concentrations (reflecting pulmonary vascular bed thrombosis with fibrinolysis) and elevated cardiac enzyme concentrations (reflecting emergent ventricular stress induced by pulmonary hypertension) in the face of normal fibrinogen and platelet levels are key early features of severe pulmonary intravascular coagulopathy related to COVID-19. Extensive immunothrombosis over a wide pulmonary vascular territory without confirmation of COVID-19 viraemia in early disease best explains the adverse impact of male sex, hypertension, obesity, and diabetes on the prognosis of patients with COVID-19. The immune mechanism underlying diffuse alveolar and pulmonary interstitial inflammation in COVID-19 involves a MAS-like state that triggers extensive immunothrombosis, which might unmask subclinical cardiovascular disease and is distinct from the MAS and disseminated intravascular coagulation that is more familiar to rheumatologists.

The burden of laboratory-confirmed influenza infection in Lebanon between 2008 and 2016: a single tertiary care center experience

BACKGROUND

Influenza is a major cause of morbidity and mortality worldwide. Following the 2009 pandemic, there was widened interest in studying influenza burden in all regions. However, since data from the World Health Organization (WHO) Middle East and North Africa (MENA) region remain limited, we aimed to contribute to the understanding of influenza burden in Lebanon.

METHODS

A retrospective chart review extending over a period of 8 seasons from Jan 1st, 2008 till June 30th, 2016 at a tertiary care center in Beirut was performed. All cases confirmed to have influenza based on rapid antigen detection or/and polymerase chain reaction on a respiratory sample were included for analysis. Data on epidemiology, clinical presentation, complications, antiviral use and mortality were collected for analysis.

RESULTS

A total of 1829 cases of laboratory-confirmed influenza were identified. Average annual positivity rate was 14% (positive tests over total requested). Both influenza A and B co-circulated in each season with predominance of influenza A. Influenza virus started circulating in December and peaked in January and February. The age group of 19-50 years accounted for the largest proportion of cases (22.5%) followed by the age group of 5-19 years (18%). Pneumonia was the most common complication reported in 33% of cases. Mortality reached 3.8%. The two extremes of age (< 2 years and ≥ 65 years) were associated with a more severe course of disease, hospitalization, intensive care unit (ICU) admission, complications, and mortality rate. Of all the identified cases, 26% were hospitalized. Moderate-to-severe disease was more likely in influenza B cases but no difference in mortality was reported between the two types. Antivirals were prescribed in 68.8% and antibiotics in 41% of cases. There seemed to be an increasing trend in the number of diagnosed and hospitalized cases over the years of the study.

CONCLUSION

Patients with laboratory-confirmed influenza at our center had a high rate of hospitalization and mortality. A population based prospective surveillance study is needed to better estimate the burden of Influenza in Lebanon that would help formulate a policy on influenza control.

Emerging respiratory infections: The infectious disease pathology of SARS, MERS, pandemic influenza, and Legionella

Lower respiratory infections remain one of the top global causes of death and the emergence of new diseases continues to be a concern. In the first two decades of the 21st century, we have born witness to the emergence of newly recognized coronaviruses that have rapidly spread around the globe, including severe acute respiratory syndrome virus (SARS) and Middle Eastern respiratory syndrome virus (MERS). We have also experienced the emergence of a novel H1N1 pandemic influenza strain in 2009 that caused substantial morbidity and mortality around the world and has transitioned into a seasonal strain. Although we perhaps most frequently think of viruses when discussing emerging respiratory infections, bacteria have not been left out of the mix, as we have witnessed an increase in the number of infections from Legionella spp. since the organisms' initial discovery in 1976. Here, we explore the basic epidemiology, clinical presentation, histopathology, and clinical laboratory diagnosis of these four pathogens and emphasize themes in humans' evolving relationship with our natural environment that have contributed to the infectious burden. Histology alone is rarely diagnostic for these infections, but has been crucial to bettering our understanding of these diseases. Together, we rely on the diagnostic acumen of pathologists to identify the clinicopathologic features that raise the suspicion of these diseases and lead to the early control of the spread in our populations.

Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenzaa

These clinical practice guidelines are an update of the guidelines published by the Infectious Diseases Society of America (IDSA) in 2009, prior to the 2009 H1N1 influenza pandemic. This document addresses new information regarding diagnostic testing, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal influenza. It is intended for use by primary care clinicians, obstetricians, emergency medicine providers, hospitalists, laboratorians, and infectious disease specialists, as well as other clinicians managing patients with suspected or laboratory-confirmed influenza. The guidelines consider the care of children and adults, including special populations such as pregnant and postpartum women and immunocompromised patients.

Clinical Practice Guidelines by the Infectious Diseases Society of America: 2018 Update on Diagnosis, Treatment, Chemoprophylaxis, and Institutional Outbreak Management of Seasonal Influenzaa

These clinical practice guidelines are an update of the guidelines published by the Infectious Diseases Society of America (IDSA) in 2009, prior to the 2009 H1N1 influenza pandemic. This document addresses new information regarding diagnostic testing, treatment and chemoprophylaxis with antiviral medications, and issues related to institutional outbreak management for seasonal influenza. It is intended for use by primary care clinicians, obstetricians, emergency medicine providers, hospitalists, laboratorians, and infectious disease specialists, as well as other clinicians managing patients with suspected or laboratory-confirmed influenza. The guidelines consider the care of children and adults, including special populations such as pregnant and postpartum women and immunocompromised patients.

Influenza vaccination and myocarditis among patients receiving immune checkpoint inhibitors

Background

Influenza vaccination (FV) is recommended for patients with cancer. Recent data suggested that the administration of the FV was associated with an increase in immune-related adverse events (irAEs) among patients on immune checkpoint inhibitors (ICIs). Myocarditis is an uncommon but serious complication of ICIs and may also result from infection with influenza. There are no data testing the relationship between FV and the development of myocarditis on ICIs.

Methods

Patients on ICIs who developed myocarditis (n = 101) (cases) were compared to ICI-treated patients (n = 201) without myocarditis (controls). A patient was defined as having the FV if they were administered the FV from 6 months prior to start of ICI to anytime during ICI therapy. Alternate thresholds for FV status were also tested. The primary comparison of interest was the rate of FV between cases and controls. Patients with myocarditis were followed for major adverse cardiac events (MACE), defined as the composite of cardiogenic shock, cardiac arrest, hemodynamically significant complete heart block and cardiovascular death.

Results

The FV was administered to 25% of the myocarditis cases compared to 40% of the non-myocarditis ICI-treated controls (p = 0.01). Similar findings of lower rates of FV administration were noted among myocarditis cases when alternate thresholds were tested. Among the myocarditis cases, those who were vaccinated had 3-fold lower troponin levels when compared to unvaccinated cases (FV vs. No FV: 0.12 [0.02, 0.47] vs. 0.40 [0.11, 1.26] ng/ml, p = 0.02). Within myocarditis cases, those administered the FV also had a lower rate of other irAEs when compared to unvaccinated cases (36 vs. 55% p = 0.10) including lower rates of pneumonitis (12 vs. 36%, p = 0.03). During follow-up (175 [IQR 89, 363] days), 47% of myocarditis cases experienced a MACE. Myocarditis cases who received the FV were at a lower risk of cumulative MACE when compared to unvaccinated cases (24 vs. 59%, p = 0.002).

Conclusion

The rate of FV among ICI-related myocarditis cases was lower than controls on ICIs who did not develop myocarditis. In those who developed myocarditis related to an ICI, there was less myocardial injury and a lower risk of MACE among those who were administered the FV.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0535-y) contains supplementary material, which is available to authorized users.

Monocytes accumulate in the airways of children with fatal asthma

BACKGROUND

Activated T helper type 2 (Th2) cells are believed to play a pivotal role in allergic airway inflammation, but which cells attract and activate Th2 cells locally have not been fully determined. Recently, it was shown in an experimental human model of allergic rhinitis (AR) that activated monocytes rapidly accumulate in the nasal mucosa after local allergen challenge, where they promote recruitment of Th2 cells and eosinophils.

OBJECTIVE

To investigate whether monocytes are recruited to the lungs in paediatric asthma.

METHODS

Tissue samples obtained from children and adolescents with fatal asthma attack (n = 12), age-matched non-atopic controls (n = 9) and allergen-challenged AR patients (n = 8) were subjected to in situ immunostaining.

RESULTS

Monocytes, identified as CD68+S100A8/A9+ cells, were significantly increased in the lower airway mucosa and in the alveoli of fatal asthma patients compared with control individuals. Interestingly, cellular aggregates containing CD68+S100A8/A9+ monocytes obstructing the lumen of bronchioles were found in asthmatics (8 out of 12) but not in controls. Analysing tissue specimens from challenged AR patients, we confirmed that co-staining with CD68 and S100A8/A9 was a valid method to identify recently recruited monocytes. We also showed that the vast majority of accumulating monocytes both in the lungs and in the nasal mucosa expressed matrix metalloproteinase 10, suggesting that this protein may be involved in their migration within the tissue.

CONCLUSIONS AND CLINICAL RELEVANCE

Monocytes accumulated in the lungs of children and adolescents with fatal asthma attack. This finding strongly suggests that monocytes are directly involved in the immunopathology of asthma and that these pro-inflammatory cells are potential targets for therapy.

Bacteria meets influenza A virus: A bioluminescence mouse model of Escherichia coli O157:H7 following influenza A virus/Puerto Rico/8/34 (H1N1) strain infection

Objective

To develop a bioluminescence-labelled bacterial infection model to monitor the colonization and clearance process of Escherichia coli O157:H7 in the lungs of mice following influenza A virus/Puerto Rico/8/34 (H1N1) strain (IAV/PR8) infection.

Methods

BALB/c mice were administered IAV/PR8 or 0.01 M phosphate-buffered saline (PBS; pH 7.4) intranasally 4 days prior to intranasal administration of 1 × 10⁷ colony-forming units (CFU) of E. coli O157:H7-lux. Whole-body bioluminescent signals were monitored at 10 min, 4 h, 8 h, 12 h, 16 h and 24 h post-bacterial infection. Lung bioluminescent signals and bacterial load (CFU/g) were monitored at 4 h, 8 h, 12 h, 16 h and 24 h post-bacterial infection.

Results

Prior IAV/PR8 infection of mice resulted in a higher level of bacterial colonization and a lower rate of bacterial clearance from the lungs compared with mice treated with PBS. There were also consistent findings between the bioluminescence imaging and the CFU measurements in terms of identifying bacterial colonization and monitoring the clearance dynamics of E. coli O157:H7-lux in mouse lungs.

Conclusion

This novel bioluminescence-labelled bacterial infection model rapidly detected bacterial colonization of the lungs and monitored the clearance dynamics of E. coli O157:H7-lux following IAV/PR8 infection.

Fatal Myopericarditis Following an Influenza A (H3N2) Infection

Patient: Female, 14

Final Diagnosis: Myopericarditis

Symptoms: Cardiac tamponade • dyspnea • pericardial effusion • tachycardia

Medication: —

Clinical Procedure: Cardiopulmonary resuscitation

Specialty: Infectious Diseases

Is Kawasaki disease an infectious disorder?

Although the etiology of Kawasaki disease (KD) is largely unknown, a large body of clinical, epidemiologic, immunologic, pathologic and ultrastructural evidence suggests that an infectious agent triggers a cascade that causes the illness. However, this elusive infectious agent remains unidentified at present. Increasingly sensitive molecular methods for identifying microbial nucleic acids and proteins in tissue samples continue to rapidly emerge, and these methods should be utilized in studies on KD etiology as they become available. Identifying the etiology of this enigmatic disease remains the single most important research goal in the field, and accomplishing this goal is the best means to improve diagnosis, treatment and prevention of this potentially fatal childhood disease.

Summary of Notifiable Infectious Diseases and Conditions - United States, 2015

The Summary of Notifiable Infectious Diseases and Conditions - United States, 2015 (hereafter referred to as the summary) contains the official statistics, in tabular and graphical form, for the reported occurrence of nationally notifiable infectious diseases and conditions in the United States for 2015. Unless otherwise noted, data are final totals for 2015 reported as of June 30, 2016. These statistics are collected and compiled from reports sent by U.S. state and territories, New York City, and District of Columbia health departments to the National Notifiable Diseases Surveillance System (NNDSS), which is operated by CDC in collaboration with the Council of State and Territorial Epidemiologists (CSTE). This summary is available at https://www.cdc.gov/MMWR/MMWR_nd/index.html. This site also includes summary publications from previous years.

Mechanisms of Severe Mortality-Associated Bacterial Co-infections Following Influenza Virus Infection

Influenza virus infection remains one of the largest disease burdens on humans. Influenza-associated bacterial co-infections contribute to severe disease and mortality during pandemic and seasonal influenza episodes. The mechanisms of severe morbidity following influenza-bacteria co-infections mainly include failure of an antibacterial immune response and pathogen synergy. Moreover, failure to resume function and tolerance might be one of the main reasons for excessive mortality. In this review, recent advances in the study of mechanisms of severe disease, caused by bacterial co-infections following influenza virus pathogenesis, are summarized. Therefore, understanding the synergy between viruses and bacteria will facilitate the design of novel therapeutic approaches to prevent mortality associated with bacterial co-infections.

Histopathological Findings of Lung with A/H1N1pdm09 Infection-Associated Acute Respiratory Distress Syndrome in the Post-Pandemic Season

We herein report the pulmonary histopathological findings of an autopsy case of post-pandemic season A/H1N1pdm09 infection-associated acute respiratory distress syndrome (ARDS). The lung histology predominantly exhibited findings indicative of the exudative phase of diffuse alveolar damage, with similar inflammation severity observed in all sections. Furthermore, the lung sections only showed a few A/H1N1pdm09 antigen-positive cells along with a low viral RNA copy number. The sequence of the viral hemagglutinin receptor binding site identified a preference for α-2,6 linked sialic acid, suggesting low alveolar epithelial cell infectivity. The pathological findings, in this case, differed in several aspects from those of the first autopsy case of A/H1N1pdm09 infection-associated ARDS in Japan, reported during the 2009 pandemic season. In conclusion, pathological and molecular biological examinations suggested that in the post-pandemic season A/H1N1pdm09 infection, the infection-associated ARDS was not caused by direct infection-induced damage to the alveolar epithelial cells but was rather a result of indirect sepsis-mediated endothelial cell damage.

Influenza virus

El virus de la influenza es un importante agente patógeno humano que causa infecciones respira-torias y una considerable morbimortalidad anual a nivel mundial. El virus puede circular esporádicamente durante brotes locales como parte de una epidemia estacional o puede generar una pandemia mundial.

Effect of an Echinacea-Based Hot Drink Versus Oseltamivir in Influenza Treatment: A Randomized, Double-Blind, Double-Dummy, Multicenter, Noninferiority Clinical Trial

BACKGROUND

Echinacea has antiviral activity against influenza viruses in vitro and has traditionally been used for treatment of colds and flu.

OBJECTIVES

This randomized, double-blind, double-dummy, multicenter, controlled clinical trial compared a new echinacea formulation with the neuraminidase inhibitor oseltamivir, the gold standard treatment for influenza.

METHODS

Following informed consent, 473 patients with early influenza symptoms (≤48 hours) were recruited in primary care in the Czech Republic and randomized to either 5 days of oseltamivir followed by 5 days of placebo, or 10 days of an Echinacea purpurea-based formulation called Echinaforce Hotdrink (A. Vogel Bioforce AG, Roggwil, Switzerland). The proportion of recovered patients (influenza symptoms rated as absent or mild in the evening) was analyzed for noninferiority between treatment groups using a generalized Wilcoxon test with significance level α = 0.05 (2-sided) and using a CI approach in the per-protocol sample.

RESULTS

Recovery from illness was comparable in the 2 treatment groups at 1.5% versus 4.1% after 1 day, 50.2% versus 48.8% after 5 days, and 90.1% versus 84.8% after 10 days of treatment with Echinaforce Hotdrink and oseltamivir, respectively. Noninferiority was demonstrated for each day and overall (95% CI, 0.487-0.5265 by generalized Wilcoxon test). Very similar results were obtained in the group with virologically confirmed influenza virus infections and in a retrospective analysis during the peak influenza period. The incidence of complications was lower with Echinaforce Hotdrink than with oseltamivir (2.46% vs 6.45%; P = 0.076) and fewer adverse events (particularly nausea and vomiting) were observed with Echinaforce Hotdrink.

CONCLUSIONS

Echinaforce Hotdrink is as effective as oseltamivir in the early treatment of clinically diagnosed and virologically confirmed influenza virus infections with a reduced risk of complications and adverse events. It appears to be an attractive treatment option, particularly suitable for self-care. Clinical trial identifier: Eudra-CT: 2010-021571-88. (Curr Ther Res Clin Exp. 2015; 77:66-72).

One health, multiple challenges: The inter-species transmission of influenza A virus

Influenza A viruses are amongst the most challenging viruses that threaten both human and animal health. Influenza A viruses are unique in many ways. Firstly, they are unique in the diversity of host species that they infect. This includes waterfowl (the original reservoir), terrestrial and aquatic poultry, swine, humans, horses, dog, cats, whales, seals and several other mammalian species. Secondly, they are unique in their capacity to evolve and adapt, following crossing the species barrier, in order to replicate and spread to other individuals within the new species. Finally, they are unique in the frequency of inter-species transmission events that occur. Indeed, the consequences of novel influenza virus strain in an immunologically naïve population can be devastating. The problems that influenza A viruses present for human and animal health are numerous. For example, influenza A viruses in humans represent a major economic and disease burden, whilst the poultry industry has suffered colossal damage due to repeated outbreaks of highly pathogenic avian influenza viruses. This review aims to provide a comprehensive overview of influenza A viruses by shedding light on interspecies virus transmission and summarising the current knowledge regarding how influenza viruses can adapt to a new host.

Pathology of Equine Influenza virus (H3N8) in Murine Model

Equine influenza viruses (EIV)—H3N8 continue to circulate in equine population throughout the world. They evolve by the process of antigenic drift that leads to substantial change in the antigenicity of the virus, thereby necessitating substitution of virus strain in the vaccines. This requires frequent testing of the new vaccines in the in vivo system; however, lack of an appropriate laboratory animal challenge model for testing protective efficacy of equine influenza vaccine candidates hinders the screening of new vaccines and other therapeutic approaches. In the present investigation, BALB/c mouse were explored for suitability for conducting pathogenecity studies for EIV. The BALB/c mice were inoculated intranasally @ 2×10^6.24 EID₅₀ with EIV (H3N8) belonging to Clade 2 of Florida sublineage and monitored for setting up of infection and associated parameters. All mice inoculated with EIV exhibited clinical signs viz. loss in body weights, lethargy, dyspnea, etc, between 3 and 5 days which commensurate with lesions observed in the respiratory tract including rhinitis, tracheitis, bronchitis, bronchiolitis, alveolitis and diffuse interstitial pneumonia. Transmission electron microscopy, immunohistochemistry, virus quantification through titration and qRT-PCR demonstrated active viral infection in the upper and lower respiratory tract. Serology revealed rise in serum lactate dehydrogenase levels along with sero-conversion. The pattern of disease progression, pathological lesions and virus recovery from nasal washings and lungs in the present investigations in mice were comparable to natural and experimental EIV infection in equines. The findings establish BALB/c mice as small animal model for studying EIV (H3N8) infection and will have immense potential for dissecting viral pathogenesis, vaccine efficacy studies, preliminary screening of vaccine candidates and antiviral therapeutics against EIV.

Management of fulminant myocarditis: a diagnosis in search of its etiology but with therapeutic options

Fulminant myocarditis is a clinical syndrome with signs of acute heart failure, cardiogenic shock, or life-threating rhythm disturbances in the context of suspected myocarditis. It is not an etiological diagnosis, but may have different underlying causes and pathogenetic processes - viral, bacterial, toxic, and autoreactive. Clinical management of the disease entity at the acute stage involves hemodynamic monitoring in an intensive care unit or similar setting. Rapid routine work-up is mandatory with serial EKGs, echocardiography, cardiac MRI, heart catheterization with endomyocardial biopsy for histology, immunohistology, and molecular analysis for the underlying infection and pathogenesis. Heart failure therapy is warranted in all cases according to current guidelines. For fulminant autoreactive myocarditis, immunosuppressive treatment is beneficial; for viral myocarditis, IVIg can resolve the inflammation, reduce the viral load, and even eradicate the microbial agent. ECMO, IABP, ventricular assist devices, LifeVest, or ICD implantation can bridge to recovery or to heart transplantation.

A case of community-acquired pneumonia due to influenza A virus and Nocardia farcinica co-infection

Nocardia spp. has not been reported previously as a cause of post-influenza pneumonia. Here we present a first case of post-influenza bacterial pneumonia due to Nocardia farcinica. Initial reason for hospitalization of the 90 year old female patient was a pneumonia with the symptoms of fever and productive cough. A rapid test for influenza antigen was positive for influenza A virus. Treatment with Zanamivir and piperacillin was initiated. However, after 1 week of treatment, the infiltration shadows on chest X-ray had worsened. Because the expectorated sputum collected on admission for culture was found to be positive for Nocardia spp., piperacillin was replaced with trimethoprim/sulfamethoxazole, and a chest X-ray showed some improvement. Although pulmonary nocardiosis with co-infection with influenza A is extremely rare, clinicians should be alert to the possibility.

The pathology and pathogenesis of experimental severe acute respiratory syndrome and influenza in animal models

Respiratory viruses that emerge in the human population may cause high morbidity and mortality, as well as concern about pandemic spread. Examples are severe acute respiratory syndrome coronavirus (SARS-CoV) and novel variants of influenza A virus, such as H5N1 and pandemic H1N1. Different animal models are used to develop therapeutic and preventive measures against such viruses, but it is not clear which are most suitable. Therefore, this review compares animal models of SARS and influenza, with an emphasis on non-human primates, ferrets and cats. Firstly, the pathology and pathogenesis of SARS and influenza are compared. Both diseases are similar in that they affect mainly the respiratory tract and cause inflammation and necrosis centred on the pulmonary alveoli and bronchioles. Important differences are the presence of multinucleated giant cells and intra-alveolar fibrosis in SARS and more fulminant necrotizing and haemorrhagic pneumonia in H5N1 influenza. Secondly, the pathology and pathogenesis of SARS and influenza in man and experimental animals are compared. Host species, host age, route of inoculation, location of sampling and timing of sampling are important to design an animal model that most closely mimics human disease. The design of appropriate animal models requires an accurate pathological description of human cases, as well as a good understanding of the effect of experimental variables on disease outcome.

Repetitive fulminant influenza myocarditis requiring the use of circulatory assist devices

A 52-year-old man was admitted to our hospital due to shortness of breath that developed one week after the diagnosis of influenza infection. He had a past history of myocarditis associated with influenza B infection 16 years before the current admission. The patient's left ventricular function showed diffuse hypokinesis with a left ventricular ejection fraction of 28%. Due to the progression of heart failure, the infusion of catecholamines and insertion of an intra-aortic balloon pump were required. The patient was discharged uneventfully on the 23rd hospital day. A significant increase in the serum antibody titer against influenza A virus subtype H3N2 led to a diagnosis of recurrent fulminant influenza myocarditis.

The complex link between influenza and severe sepsis

Severe sepsis is traditionally associated with bacterial diseases. While fungi and parasites can also cause sepsis, they are significantly less common than bacterial causes. However, viruses are becoming a growing cause of severe sepsis worldwide. Among these viruses, influenza is crossing all geographic boundaries and is causing larger epidemics and pandemics. As a consequence, more critically ill patients with severe sepsis caused directly by influenza viruses, or indirectly by influenza-induced secondary bacterial infections are being admitted to hospitals worldwide. This manuscript aims to provide a pathophysiological and clinical update on the link between influenza and severe sepsis.

Cytokine and chemokine profiles in lung tissues from fatal cases of 2009 pandemic influenza A (H1N1): role of the host immune response in pathogenesis

Pathological studies on fatal cases caused by 2009 pandemic influenza H1N1 virus (2009 pH1N1) reported extensive diffuse alveolar damage and virus infection predominantly in the lung parenchyma. However, the host immune response after severe 2009 pH1N1 infection is poorly understood. Herein, we investigated viral load, the immune response, and apoptosis in lung tissues from 50 fatal cases with 2009 pH1N1 virus infection. The results suggested that 7 of the 27 cytokines/chemokines showed remarkably high expression, including IL-1 receptor antagonist protein, IL-6, tumor necrosis factor-α, IL-8, monocyte chemoattractant protein-1, macrophage inflammatory protein 1-β, and interferon-inducible protein-10 in lung tissues of 2009 pH1N1 fatal cases. Viral load, which showed the highest level on day 7 of illness onset and persisted until day 17 of illness, was positively correlated with mRNA levels of IL-1 receptor antagonist protein, monocyte chemoattractant protein-1, macrophage inflammatory protein 1-β, interferon-inducible protein-10, and regulated on activation normal T-cell expressed and secreted. Apoptosis was evident in lung tissues stained by the TUNEL assay. Decreased Fas and elevated FasL mRNA levels were present in lung tissues, and cleaved caspase-3 was frequently seen in pneumocytes, submucosal glands, and lymphoid tissues. The pathogenesis of the 2009 pH1N1 virus infection is associated with viral replication and production of proinflammatory mediators. FasL and caspase-3 are involved in the pathway of 2009 pH1N1 virus-induced apoptosis in lung tissues, and the disequilibrium between the Fas and FasL level in lung tissues could contribute to delayed clearance of the virus and subsequent pathological damages.

The battle between influenza and the innate immune response in the human respiratory tract

Influenza is a viral infection of the respiratory tract. Infection is normally confined to the upper respiratory tract but certain viral strains have evolved the ability to infect the lower respiratory tract, including the alveoli, leading to inflammation and a disease pattern of diffuse alveolar damage. Factors leading to this sequence of events are novel influenza strains, or strains that have viral proteins, in particular the NS1 protein that allow it to escape the innate immune system. There are three main barriers that prevent infection of pneumocytes - mucin, host defence lectins and cells such as macrophages. Viruses have developed strategies such as neuraminidase and glycosylation patterns that allow this evasion. Though there has been much investment in antiviral drugs, it is proposed that more attention should be directed towards developing or utilizing compounds that enhance the ability of the innate immune system to combat viral infection.

The cardiovascular manifestations of influenza: a systematic review

Influenza accounts for 3 to 5 million cases of severe illness and up to 300,000 deaths annually, presenting a considerable burden to healthcare services. A spectrum of cardiovascular complications has been reported in association with influenza infection. This can occur through direct effects of the virus on the myocardium or through exacerbation of existing cardiovascular disease. Direct myocardial involvement presenting as myocarditis is not uncommon during influenza infection. Clinical presentation may vary from asymptomatic to fulminant myocarditis resulting in cardiogenic shock and death. Cardiovascular mortality is also increased during influenza epidemics in patients with pre-existing coronary artery disease. Rates of myocardial infarction have been shown to increase following influenza outbreaks, whilst decreases in cardiovascular mortality have been demonstrated following influenza vaccination in high risk patients. The purpose of this review is to provide an overview of cardiovascular complications, their presentation, clinical course and the management options available following influenza infection.

In vivo and in vitro studies on the roles of neutrophil extracellular traps during secondary pneumococcal pneumonia after primary pulmonary influenza infection

Seasonal influenza virus infections may lead to debilitating disease, and account for significant fatalities annually worldwide. Most of these deaths are attributed to the complications of secondary bacterial pneumonia. Evidence is accumulating to support the notion that neutrophil extracellular traps (NETs) harbor several antibacterial proteins, and trap and kill bacteria. We have previously demonstrated the induction of NETs that contribute to lung tissue injury in severe influenza pneumonia. However, the role of these NETs in secondary bacterial pneumonia is unclear. In this study, we explored whether NETs induced during pulmonary influenza infection have functional significance against infections with Streptococcus pneumoniae and other bacterial and fungal species. Our findings revealed that NETs do not participate in killing of Streptococcus pneumoniae in vivo and in vitro. Dual viral and bacterial infection elevated the bacterial load compared to animals infected with bacteria alone. Concurrently, enhanced lung pathogenesis was observed in dual-infected mice compared to those challenged with influenza virus or bacteria alone. The intensified NETs in dual-infected mice often appeared as clusters that were frequently filled with partially degraded DNA, as evidenced by punctate histone protein staining. The severe pulmonary pathology and excessive NETs generation in dual infection correlated with exaggerated inflammation and damage to the alveolar-capillary barrier. NETs stimulation in vitro did not significantly alter the gene expression of several antimicrobial proteins, and these NETs did not exhibit any bactericidal activity. Fungicidal activity against Candida albicans was observed at similar levels both in presence or absence of NETs. These results substantiate that the NETs released by primary influenza infection do not protect against secondary bacterial infection, but may compromise lung function.

Pathological study of archival lung tissues from five fatal cases of avian H5N1 influenza in Vietnam

Highly pathogenic avian H5N1 influenza virus (H5N1) infection in humans causes acute respiratory distress syndrome, leading to multiple organ failure. Five fatal cases of H5N1 infection in Vietnam were analyzed pathologically to reveal virus distribution, and local proinflammatory cytokine and chemokine expression profiles in formalin-fixed, paraffin-embedded lung tissues. Our main histopathological findings showed diffuse alveolar damage in the lungs. The infiltration of myeloperoxidase-positive and/or CD68 (clone KP-1)-positive neutrophils and monocytes/macrophages was remarkable in the alveolar septa and alveolar spaces. Immunohistochemistry revealed that H5N1 mainly infected alveolar epithelial cells and monocytes/macrophages in lungs. H5N1 replication was confirmed by detecting H5N1 mRNA in epithelial cells using in situ hybridization. Quantitation of H5N1 RNA using quantitative reverse transcription PCR assays revealed that the level of H5N1 RNA was increased in cases during early phases of the disease. We quantified the expression of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-8, regulated on activation normal T-cell expressed and secreted (commonly known as RANTES), and interferon-gamma-inducible protein of 10 kDa (IP-10) in formalin-fixed, paraffin-embedded lung sections. Their expression levels correlated with H5N1 RNA copy numbers detected in the same lung region. Double immunofluorescence staining revealed that TNF-α, IL-6, IL-8 and IP-10 were expressed in epithelial cells and/or monocytes/macrophages. In particular, IL-6 was also expressed in endothelial cells. The dissemination of H5N1 beyond respiratory organs was not confirmed in two cases examined in this study.

Localization of pandemic 2009 H1N1 influenza A virus RNA in lung and lymph nodes of fatal influenza cases by in situ hybridization: new insights on virus replication and pathogenesis

BACKGROUND

Pandemic 2009 H1N1 influenza A (pH1N1) virus has caused substantial morbidity and mortality globally and continues to circulate. Although pH1N1 viral antigens have been demonstrated in various human tissues by immunohistochemistry (IHC), cellular localization of pH1N1 RNA in these tissues has largely remained uninvestigated.

OBJECTIVES

To examine the distribution of pH1N1 RNA in tissues of fatal cases in order to understand the virus tissue tropism, replication and disease pathogenesis.

STUDY DESIGN

Formalin-fixed, paraffin embedded autopsy tissues from 21 patients with confirmed pH1N1 infection were analyzed by influenza A IHC and by in situ hybridization (ISH) using DIG-labeled sense (detects viral RNA) and antisense probes (detects positive-stranded mRNA and cRNA) targeting the nucleoprotein gene of pH1N1 virus.

RESULTS

pH1N1 RNA was localized by ISH in 57% of cases while viral antigens were detected by IHC in 76%. However, in cases with a short duration of illness (1-3 days), more cases (69%) were positive by ISH than IHC (62%). Strong ISH staining was detected by antisense probes in the alveolar pneumocytes of the lungs, mucous glands and in lymph nodes. IHC staining of viral antigens was demonstrated in the lung pneumocytes and mucous glands, but no immunostaining was detected in any of the lymph nodes examined.

CONCLUSIONS

This study demonstrates cellular localization of positive-stranded pH1N1 RNA in the lungs, mucous glands and lymph nodes that suggests viral replication in these tissues. The novel ISH assay can be a useful adjunct for the detection of pH1N1 virus in tissues and for pathogenesis studies.

Linking influenza virus tissue tropism to population-level reproductive fitness

Influenza virus tissue tropism defines the host cells and tissues that support viral replication and contributes to determining which regions of the respiratory tract are infected in humans. The location of influenza virus infection along the respiratory tract is a key determinant of virus pathogenicity and transmissibility, which are at the basis of influenza burdens in the human population. As the pathogenicity and transmissibility of influenza virus ultimately determine its reproductive fitness at the population level, strong selective pressures will shape influenza virus tissue tropisms that maximize fitness. At present, the relationships between influenza virus tissue tropism within hosts and reproductive fitness at the population level are poorly understood. The selective pressures and constraints that shape tissue tropism and thereby influence the location of influenza virus infection along the respiratory tract are not well characterized. We use mathematical models that link within-host infection dynamics in a spatially-structured human respiratory tract to between-host transmission dynamics, with the aim of characterizing the possible selective pressures on influenza virus tissue tropism. The results indicate that spatial heterogeneities in virus clearance, virus pathogenicity or both, resulting from the unique structure of the respiratory tract, may drive optimal receptor binding affinity--that maximizes influenza virus reproductive fitness at the population level--towards sialic acids with α2,6 linkage to galactose. The expanding cell pool deeper down the respiratory tract, in association with lower clearance rates, may result in optimal infectivity rates--that likewise maximize influenza virus reproductive fitness at the population level--to exhibit a decreasing trend towards deeper regions of the respiratory tract. Lastly, pre-existing immunity may drive influenza virus tissue tropism towards upper regions of the respiratory tract. The proposed framework provides a new template for the cross-scale study of influenza virus evolutionary and epidemiological dynamics in humans.

The role of postmortem studies in pneumonia etiology research

The diagnosis of etiology in severe pneumonia remains a challenging area. Postmortem lung tissue potentially increases the sensitivity of investigations for identification of causative pathogens in fatal cases of pneumonia and can confirm antemortem microbiological diagnoses. Tissue sampling allows assessment of histological patterns of disease and ancillary immunohistochemical or molecular diagnostic techniques. It may also enhance the recognition of noninfectious conditions that clinically simulate acute pneumonia. Biobanking of lung tissue or postmortem culture isolates offers opportunities for new pathogen discovery and research into host-pathogen interactions. The Pneumonia Etiology Research for Child Health study proposes a percutaneous needle biopsy approach to obtain postmortem samples, rather than a full open autopsy. This has the advantage of greater acceptability to relatives, but risks greater sampling error. Both approaches may be susceptible to microbiological contamination or pathogen degradation. However, previous autopsy studies have confirmed the value of histological examination in revealing unsuspected pathogens and influencing clinical guidelines for the diagnosis and treatment of future pneumonia cases.

2009 H1N1 fatalities: the New Mexico experience

Histopathologic features of New Mexico 2009 H1N1 fatalities have not been representative of those reported nationwide. We retrospectively reviewed medical records of all New Mexico 2009 pandemic influenza A (pH1N1) fatalities (n = 50). In cases in which autopsy was performed (n = 12), histologic sections and culture results were examined. In contrast to previously published studies, the majority of our fatalities did not have diffuse alveolar damage (DAD) (2/12; 16.7%). Common findings included pulmonary interstitial inflammation and edema, tracheobronchitis, and pneumonia. Two cases had significant extra-pulmonary manifestations: myocarditis and cerebral edema with herniation. The majority had a rapid disease course: range from 1 to 12 days (median, 2 days), and Native Americans were disproportionately represented among fatalities. These findings suggest that New Mexico H1N1 fatalities generally did not survive long enough to develop the classic picture of DAD. Pathologists should be aware that H1N1 may cause extra-pulmonary pathology and perform postmortem cultures and histologic sampling accordingly.

Pathogenesis of influenza virus infections: the good, the bad and the ugly

The clinical outcome of different influenza virus infections ranges from subclinical upper respiratory tract disease to fatal lower respiratory tract disease. An important determinant in the pathogenesis of these diseases is the tissue tropism of the influenza virus. Furthermore, virulence is often correlated with virus replication and is regulated by multiple virus genes. Host defense against virus infection consists of both innate and adaptive immune responses. However, excessive or dysbalanced immune response may result in lung tissue damage, reduced respiratory capacity, and severe disease or even death. By interdisciplinary efforts to better understand the intricate interaction between virus, tissue, and immune response, we may be able to find new ways to improve the outcome of influenza virus infections.

The role of cell tropism for the pathogenesis of influenza in humans

Seasonal, pandemic and avian influenza viruses are able to infect humans, but the disease outcome often differs, ranging from mild upper respiratory tract disease to fatal pneumonia. The cell tropism of influenza viruses is thought to be an important determinant of these factors. Therefore, this review focuses on the factors that, together, determine the cell tropism of influenza viruses. These include: the receptor specificity of the viral hemagglutinin and the distribution of these receptors in the respiratory tract; the presence of inhibitory factors in the fluid lining the respiratory mucosa; and the requirement for host cell proteases that can cleave the precursor hemagglutinin of influenza viruses. Finally, we will discuss how the route of inoculation influences the cell types infected by influenza viruses and associated pathogenesis.

Myocardial injury and bacterial pneumonia contribute to the pathogenesis of fatal influenza B virus infection

BACKGROUND

Influenza B virus infection causes rates of hospitalization and influenza-associated pneumonia similar to seasonal influenza A virus infection and accounts for a substantial percentage of all influenza-related hospitalizations and deaths among those aged <18 years; however, the pathogenesis of fatal influenza B virus infection is poorly described.

METHODS

Tissue samples obtained at autopsy from 45 case patients with fatal influenza B virus infection were evaluated by light microscopy and immunohistochemical assays for influenza B virus, various bacterial pathogens, and complement components C4d and C9, to identify the cellular tropism of influenza B virus, characterize concomitant bacterial pneumonia, and describe the spectrum of cardiopulmonary injury.

RESULTS

Viral antigens were localized to ciliated respiratory epithelium and cells of submucosal glands and ducts. Concomitant bacterial pneumonia, caused predominantly by Staphylococcus aureus, was identified in 38% of case patients and occurred with significantly greater frequency in those aged >18 years. Pathologic evidence of myocardial injury was identified in 69% of case patients for whom cardiac tissue samples were available for examination, predominantly in case patients aged <18 years.

CONCLUSIONS

Our findings suggest that bacterial pneumonia and cardiac injury contribute to fatal outcomes after infection with influenza B virus and that the frequency of these manifestations may be age related.