Does ribavirin impact on the hospital course of children with respiratory syncytial virus (RSV) infection? An analysis using the pediatric investigators collaborative network on infections in Canada (PICNIC) RSV database

Bronchiolitis therapies and misadventures

Viral bronchiolitis, which is most commonly caused by an infection with the respiratory syncytial virus (RSV), can lead to respiratory difficulties in young children which may require hospitalization. Despite years of research and medical trials, the mainstay of bronchiolitis treatment remains supportive only. This review provides an overview of the history of different treatments for bronchiolitis, including those that failed, as well as new therapies that are under study. Future studies for the treatment of bronchiolitis should consider different age-groups, important subgroups (i.e., those with a prior history of wheezing, those with a family history of asthma and those with non-RSV viral etiologies) whose response to treatment may differ from that of the composite group.

Inhibition of viral RNA-dependent RNA polymerases with clinically relevant nucleotide analogs

The treatment of viral infections remains challenging, in particular in the face of emerging pathogens. Broad-spectrum antiviral drugs could potentially be used as a first line of defense. The RNA-dependent RNA polymerase (RdRp) of RNA viruses serves as a logical target for drug discovery and development efforts. Herein we discuss compounds that target RdRp of poliovirus, hepatitis C virus, influenza viruses, respiratory syncytial virus, and the growing data on coronaviruses. We focus on nucleotide analogs and mechanisms of action and resistance.

Pharmacological targets and emerging treatments for respiratory syncytial virus bronchiolitis

RSV infection of the lower respiratory tract in infants is the leading cause of pediatric hospitalizations and second to malaria in causing infant deaths worldwide. RSV also causes substantial morbidity in immunocompromised and elderly populations. The only available therapeutic is a prophylactic drug called Palivizumab that is a humanized monoclonal antibody, given to high-risk infants. However, this intervention is expensive and has a limited impact on annual hospitalization rates caused by RSV. No vaccine is available, nor are efficacious antivirals to treat an active infection, and there is still no consensus on how infants with bronchiolitis should be treated during hospital admission. In this comprehensive review, we briefly outline the function of the RSV proteins and their suitability as therapeutic targets. We then discuss the most promising drug candidates, their inhibitory mechanisms, and whether they are in the process of clinical trials. We also briefly discuss the reasons for some of the failures in RSV therapeutics and vaccines. In summary, we provide insight into current antiviral development and the considerations toward producing licensed antivirals and therapeutics.

Anti-infective Properties of the Golden Spice Curcumin

The search for novel anti-infectives is one of the most important challenges in natural product research, as diseases caused by bacteria, viruses, and fungi are influencing the human society all over the world. Natural compounds are a continuing source of novel anti-infectives. Accordingly, curcumin, has been used for centuries in Asian traditional medicine to treat various disorders. Numerous studies have shown that curcumin possesses a wide spectrum of biological and pharmacological properties, acting, for example, as anti-inflammatory, anti-angiogenic and anti-neoplastic, while no toxicity is associated with the compound. Recently, curcumin’s antiviral and antibacterial activity was investigated, and it was shown to act against various important human pathogens like the influenza virus, hepatitis C virus, HIV and strains of Staphylococcus, Streptococcus, and Pseudomonas. Despite the potency, curcumin has not yet been approved as a therapeutic antiviral agent. This review summarizes the current knowledge and future perspectives of the antiviral, antibacterial, and antifungal effects of curcumin.

Past, Present and Future Approaches to the Prevention and Treatment of Respiratory Syncytial Virus Infection in Children

INTRODUCTION

The REGAL (RSV Evidence - A Geographical Archive of the Literature) series has provided a comprehensive review of the published evidence in the field of respiratory syncytial virus (RSV) in Western countries over the last 20 years. This seventh and final publication covers the past, present and future approaches to the prevention and treatment of RSV infection among infants and children.

METHODS

A systematic review was undertaken of publications between January 1, 1995 and December 31, 2017 across PubMed, Embase and The Cochrane Library. Studies reporting data on the effectiveness and tolerability of prophylactic and therapeutic agents for RSV infection were included. Study quality and strength of evidence (SOE) were graded using recognized criteria. A further nonsystematic search of the published literature and Clinicaltrials.gov on antiviral therapies and RSV vaccines currently in development was also undertaken.

RESULTS

The systematic review identified 1441 studies of which 161 were included. Management of RSV remains centered around prophylaxis with the monoclonal antibody palivizumab, which has proven effective in reducing RSV hospitalization (RSVH) in preterm infants < 36 weeks' gestational age (72% reduction), children with bronchopulmonary dysplasia (65% reduction), and infants with hemodynamically significant congenital heart disease (53% reduction) (high SOE). Palivizumab has also shown to be effective in reducing recurrent wheezing following RSVH (high SOE). Treatment of RSV with ribavirin has conflicting success (moderate SOE). Antibodies with increased potency and extended half-life are currently entering phase 3 trials. There are approximately 15 RSV vaccines in clinical development targeting the infant directly or indirectly via the mother.

CONCLUSION

Palivizumab remains the only product licensed for RSV prophylaxis, and only available for high-risk infants. For the general population, there are several promising vaccines and monoclonal antibodies in various stages of clinical development, with the aim to significantly reduce the global healthcare impact of this common viral infection.

FUNDING

AbbVie.

Respiratory Syncytial Virus Hospitalizations in Healthy Preterm Infants: Systematic Review

BACKGROUND

Studies have explored the risk for and impact of respiratory syncytial virus (RSV) infection requiring hospitalization among healthy preterm infants born at 29-35 weeks of gestational age not given RSV immunoprophylaxis. We performed a systematic review and qualitative synthesis of these studies.

METHODS

Two experienced reviewers used prespecified inclusion/exclusion criteria to screen titles/abstracts and full-text studies using MEDLINE, Embase, BIOSIS and Cochrane Library (January 1, 1985, to November 6, 2014). We abstracted data on risk factors for RSV hospitalization, incidence and short- and long-term outcomes of RSV hospitalization. Using standard procedures, we assessed study risk of bias and graded strength of evidence (SOE).

RESULTS

We identified 4754 records and reviewed 27. Important risk factors for RSV hospitalization included young age during the RSV season, having school-age siblings and day-care attendance, with odds ratios >2.5 in at least one study (high SOE). Incidence rates for RSV hospitalizations ranged from 2.3% to 10% (low SOE). Length of hospital stays ranged from 3.8 to 6.1 days (low SOE). Recurrent wheezing rates ranged from 20.7% to 42.8% 1 to 2 years after RSV hospitalization (low SOE).

CONCLUSIONS

Young chronological age and some environmental risk factors are important clinical indicators of an increased risk of RSV hospitalization in healthy preterm infants 32 to 35 weeks of gestational age. SOE was low for estimates of incidence of RSV hospitalizations, in-hospital resource use and recurrent wheezing in this population. Studies were inconsistent in study characteristics, including weeks of gestational age, age during RSV season and control for confounding factors.

Core bead chromatography for preparation of highly pure, infectious respiratory syncytial virus in the negative purification mode

Respiratory syncytial virus (RSV) is an important human pathogen, and is the most frequent viral cause of severe respiratory disease in infants. In addition, it is increasingly being recognized as an important cause of respiratory disease in the elderly and immunocompromised. Although a passive prophylactic treatment does exist for high-risk neonates and children, the overall disease burden warrants the development of a safe and effective prophylactic vaccine for use in otherwise healthy newborns and children. RSV is known to be an extremely labile virus, prone to aggregation and loss of infectious titer during virus handling and preparation procedures. To date infective RSV virions have been prepared by methods which are not readily scalable, such as density gradient ultracentrifugation. In this study we describe a scalable, chromatography-based purification procedure for preparation of highly pure, infectious RSV. The purification scheme is based on core bead technology and hollow fiber tangential flow filtration (TFF) and results in a ∼60% recovery of infectious virus titer. This method can be used to prepare highly purified wild type or live-attenuated vaccine strain viruses with titers as high as 1×10(8) plaque forming units per mL. A live-attenuated RSV vaccine prepared by this method was found to be immunogenic and protective in vivo, and its purity was 50-200-fold greater with respect to host cell dsDNA and Vero host cell proteins, than the raw feed stream. The results presented here can be considered a starting point for downstream process development of a live-attenuated vaccine approach for prevention of disease by RSV.

Bronchiolitis

Everyone on the planet is exposed to respiratory syncytial virus (RSV) infection by the age of 2 years. Most infants admitted to the pediatric intensive care unit (PICU) for respiratory support during this infection are previously healthy, but their principal risk for needing PICU treatment is young age. That is, if you are born in October/November in the northern hemisphere, then your first winter exposure to RSV is likely to be when you are less than 4 months of age and vulnerable because of poor respiratory mechanical reserve (Alonso et al. 2007). However, if you are born in May/June, then you will be 7–8 months during your first winter exposure to RSV, much bigger and stronger and have more efficient thoracic and diaphragmatic mechanics. In the PICU, the main predictors of severe outcome in previously well infants appear to be young age, presence of apnea, and pulmonary consolidation on admission chest radiograph (Tasker et al. 2000; Lopez Guinea et al. 2007). Taken together, we can say that more severe RSV bronchiolitis in PICU practice is typically a problem of pulmonary consolidation, poor respiratory mechanics, and poor reserve, in the younger infant.

Respiratory Syncytial Virus: pathology, therapeutic drugs and prophylaxis

Human Respiratory Syncytial Virus (hRSV) is the leading cause of lower respiratory tract diseases, affecting particularly newborns and young children. This virus is able to modulate the immune response, generating a pro-inflammatory environment in the airways that causes obstruction and pulmonary alterations in the infected host. To date, no vaccines are available for human use and the first vaccine that reached clinical trials produced an enhanced hRSV-associated pathology 50 years ago, resulting in the death of two children. Currently, only two therapeutic approaches have been used to treat hRSV infection in high risk children: 1. Palivizumab, a humanized antibody against the F glycoprotein that reduces to half the number of hospitalized cases and 2. Ribavirin, which fails to have a significant therapeutic effect. A major caveat for these approaches is their high economical cost, which highlights the need of new and affordable therapeutic or prophylactic tools to treat or prevents hRSV infection. Accordingly, several efforts are in progress to understand the hRSV-associated pathology and to characterize the immune response elicited by this virus. Currently, preclinical and clinical trials are being conducted to evaluate safety and efficacy of several drugs and vaccines, which have shown promising results. In this article, we discuss the most important advances in the development of drugs and vaccines, which could eventually lead to better strategies to treat or prevent the detrimental inflammation triggered by hRSV infection.

Respiratory syncytial virus infections in infants affected by primary immunodeficiency

Primary immunodeficiencies are rare inherited disorders that may lead to frequent and often severe acute respiratory infections. Respiratory syncytial virus (RSV) is one of the most frequent pathogens during early infancy and the infection is more severe in immunocompromised infants than in healthy infants, as a result of impaired T- and B-cell immune response unable to efficaciously neutralize viral replication, with subsequent increased viral shedding and potentially lethal lower respiratory tract infection. Several authors have reported a severe clinical course after RSV infections in infants and children with primary and acquired immunodeficiencies. Environmental prophylaxis is essential in order to reduce the infection during the epidemic season in hospitalized immunocompromised infants. Prophylaxis with palivizumab, a humanized monoclonal antibody against the RSV F protein, is currently recommended in high-risk infants born prematurely, with chronic lung disease or congenital heart disease. Currently however the prophylaxis is not routinely recommended in infants with primary immunodeficiency, although some authors propose the extension of prophylaxis to this high risk population.

Antiviral activity of carnosic acid against respiratory syncytial virus

Background

Human respiratory syncytial virus (hRSV) is a leading cause of severe lower respiratory infection and a major public health threat worldwide. To date, no vaccine or effective therapeutic agent has been developed. In a screen for potential therapeutic agents against hRSV, we discovered that an extract of Rosmarinus officinalis exerted a strong inhibitory effect against hRSV infection. Subsequent studies identified carnosic acid as a bioactive constituent responsible for anti-hRSV activity. Carnosic acid has been shown to exhibit potent antioxidant and anti-cancer activities. Anti-RSV activity of carnosic acid was further investigated in this study.

Methods

Effects of extracts from various plants and subfractions from R. officinalis on hRSV replication were determined by microneutralization assay and plaque assay. Several constituents were isolated from ethyl acetate fraction of R. officinalis and their anti-RSV activities were assessed by plaque assay as well as reverse-transcription quantitative PCR to determine the synthesis of viral RNAs.

Results

Among the tested bioactive constituents of R. officinalis, carnosic acid displayed the most potent anti-hRSV activity and was effective against both A- and B-type viruses. Carnosic acid efficiently suppressed the replication of hRSV in a concentration-dependent manner. Carnosic acid effectively suppressed viral gene expression without inducing type-I interferon production or affecting cell viability, suggesting that it may directly affect viral factors. A time course analysis showed that addition of carnosic acid 8 hours after infection still effectively blocked the expression of hRSV genes, further suggesting that carnosic acid directly inhibited the replication of hRSV.

Conclusions

The current study demonstrates that carnosic acid, a natural compound that has already been shown to be safe for human consumption, has anti-viral activity against hRSV, efficiently blocking the replication of this virus. Carnosic acid inhibited both A- and B- type hRSV, while it did not affect the replication of influenza A virus, suggesting that its antiviral activity is hRSV-specific. Collectively, this study suggests the need for further evaluation of carnosic acid as a potential treatment for hRSV.

The risk of mortality among young children hospitalized for severe respiratory syncytial virus infection

Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) is the leading cause of childhood morbidity. Although also an important cause of childhood mortality worldwide, the impact of key risk factors has not been established. A systematic review of 34 articles reporting case fatality rates in young children hospitalized for severe RSV LRTI, according to the presence of underlying RSV risk factors, was conducted. The weighted mean case fatality rate was 1.2% (range, 0-8.3%; median, 0%; n = 10) among preterm infants; 5.2% (range, 2.0-37.0%; median, 5.9%; n = 7) among children with CHD; and 4.1% (range, 0-10.5%; median, 7.0%; n = 6) among children with BPD. Case fatality estimates among children not at high risk (n = 6) ranged from 0% to 1.5% (weighted mean, 0.2%; median, 0.0%). Fatality during hospitalization for severe RSV LRTI is rare among children not at high risk, but occurs more commonly among children at higher risk of RSV LRTI.

Respiratory syncytial virus: diagnosis, treatment and prevention

Respiratory Syncytial Virus (RSV) is a common virus that infects children and adults; however, children younger than two years of age tend to develop more serious respiratory symptoms. RSV is responsible for thousands of outpatient visits (e.g., emergency room/primary care physician), hospitalizations and can result in death. Treatment is primarily supportive care and the illness resolves without complications in most children. RSV prophylaxis with palivizumab is an option for high-risk infants and children, which can decrease hospitalization and length of stay. Immunocompromised patients are a special population of which ribavirin and palivizumab may be used for treatment. Currently, no medication or vaccine available has been able to show a reduction in mortality from RSV. Future vaccines are in the developmental stage and will hopefully decrease the symptomatic and economic burden of this disease.

Impact of respiratory syncytial virus: the nurse's perspective

Respiratory syncytial virus (RSV) is a highly contagious virus, and is the major cause of lower respiratory tract infections in infants and toddlers worldwide. RSV infection poses serious health risks to young children during the first 2 years of life. Several infant populations have been classified as high risk, and additional risk factors are known to increase the likelihood of severe RSV infection. Treatment for active RSV infection is limited to the symptoms of infection rather than the underlying cause; therefore, it is critical to reduce the transmission of RSV. As nurses, we highlight the importance of educating healthcare professionals, both in the hospital and community settings, as well as parents and other caregivers about the risks and outcomes associated with RSV infection, and necessary measures to decrease the risk of infection. We also highlight the importance of the successful identification of those children who are at high risk of RSV infection. RSV prophylaxis (RSVP) with palivizumab has been shown to improve clinical outcome in infants who are considered high risk compared with those who have not received RSVP. The failure of healthcare staff and primary caregivers to protect children against an RSV infection can have lasting detrimental effects on the health and lives of affected children and their families.

Inhibition of epithelial sodium channels by respiratory syncytial virus in vitro and in vivo

Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infection in infants and children worldwide. Infection of mice with RSV decreased sodium (Na(+)) dependent alveolar fluid clearance (AFC), resulting in increased lung water content and hypoxemia. RSV infection resulted in higher levels of pyrimidines and purines in the alveolar space. Intratracheal administration of UTP or UDP also decreased AFC. The effects of RSV on AFC and oxygen saturation of Balb/c mice were reversed by intraalveolar administration of antagonists of P2Y nucleotide receptors, enzymes that enhance the breakdown of pyrimidines and systemic or intranasal administration of inhibitors of the de novo pathway of pyrimidine synthesis. RSV infection of H441 or mouse tracheal epithelial cells decreased the amiloride-sensitive Na(+) currents and pretreatment of H441 cells with A77 prevented this effect. These findings indicate that the harmful effects of RSV on lung epithelia are mediated at least in part via the production of UTP and its paracrine action on ENaC.

Prevention of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) infection is the leading cause of lower respiratory tract infection in young children, with significant numbers of premature infants and those with other risk factors requiring hospitalization in Canada each year. Palivizumab, an RSV-specific monoclonal antibody, can reduce the hospitalization rate and severity of illness for a small group of high-risk or premature infants during their first RSV season. The present statement reviews the published literature and provides recommendations regarding its use in premature and other at-risk infants, for Canadian physicians.

RNA interference-mediated silencing of the respiratory syncytial virus nucleocapsid defines a potent antiviral strategy

We describe the design and characterization of a potent human respiratory syncytial virus (RSV) nucleocapsid gene-specific small interfering RNA (siRNA), ALN-RSV01. In in vitro RSV plaque assays, ALN-RSV01 showed a 50% inhibitory concentration of 0.7 nM. Sequence analysis of primary isolates of RSV showed that the siRNA target site was absolutely conserved in 89/95 isolates, and ALN-RSV01 demonstrated activity against all isolates, including those with single-mismatch mutations. In vivo, intranasal dosing of ALN-RSV01 in a BALB/c mouse model resulted in potent antiviral efficacy, with 2.5- to 3.0-log-unit reductions in RSV lung concentrations being achieved when ALN-RSV01 was administered prophylactically or therapeutically in both single-dose and multidose regimens. The specificity of ALN-RSV01 was demonstrated in vivo by using mismatch controls; and the absence of an immune stimulatory mechanism was demonstrated by showing that nonspecific siRNAs that induce alpha interferon and tumor necrosis factor alpha lack antiviral efficacy, while a chemically modified form of ALN-RSV01 lacking measurable immunostimulatory capacity retained full activity in vivo. Furthermore, an RNA interference mechanism of action was demonstrated by the capture of the site-specific cleavage product of the RSV mRNA via rapid amplification of cDNA ends both in vitro and in vivo. These studies lay a solid foundation for the further investigation of ALN-RSV01 as a novel therapeutic antiviral agent for clinical use by humans.

Treatment of RSV bronchiolitis: drugs, antibiotics

RSV bronchiolitis is one of the most common reasons for hospital admission and for visits to emergency departments for children, and at least half of affected infants will have subsequent episodes of respiratory illness. Despite this, there are wide variations in management. Initial assessment of respiratory status should include a measure of oxygenation and oxygen should be given when there is clinical evidence of respiratory distress even before full assessment is completed. Fluid and nutritional status should also be assessed early and decisions made about use of intravenous fluids, nasogastric feeding, or maintenance of frequent feeds orally. Given the lack of evidence on all drug therapies for bronchiolitis, clinicians should carefully evaluate treatments for their ability to reduce symptoms, decrease length of hospital stay and reduce sequelae. Furthermore, clinicians should monitor antibiotic use carefully and develop a strategy to change current physician practice.

Role of ventilation in RSV disease: CPAP, ventilation, HFO, ECMO

Respiratory syncytial virus (RSV) lower respiratory tract disease may present as bronchiolitis, an obstructive lung disease with hyperinflation, or pneumonitis, a restrictive parenchymal disease with diffuse consolidation, a large intrapulmonary shunt and acute respiratory distress syndrome (ARDS). Although a significant proportion of those admitted to hospital will require some form of respiratory support, there have been few randomised studies to determine which is the most beneficial. Studies on the use of continuous positive airway pressure (CPAP), heliox, inhaled nitric oxide, and natural surfactant are reviewed. Current practice regarding ventilator support is largely based on clinical judgment and case reports. Multicentre randomised trials with long-term follow-ups are urgently required.

Inhibition of Na+ transport in lung epithelial cells by respiratory syncytial virus infection

We investigated the mechanisms by which respiratory syncytial virus (RSV) infection decreases vectorial Na+ transport across respiratory epithelial cells. Mouse tracheal epithelial (MTE) cells from either BALB/c or C57BL/6 mice and human airway H441 cells were grown on semipermeable supports under an air-liquid interface. Cells were infected with RSV-A2 and mounted in Ussing chambers for measurements of short-circuit currents (I(sc)). Infection with RSV for 24 hours (multiplicity of infection = 1) resulted in positive immunofluorescence for RSV antigen in less than 10% of MTE or H441 cells. In spite of the limited number of cells infected, RSV reduced both basal and amiloride-sensitive I(sc) in both MTE and H441 cells by approximately 50%, without causing a concomitant reduction in transepithelial resistance. Agents that increased intracellular cAMP (forskolin, cpt-CAMP, and IBMX) increased mainly Cl(-) secretion in MTE cells and Na+ absorption in H441 cells. RSV infection for 24 hours blunted both variables. In contrast, ouabain sensitive I(sc), measured across apically permeabilized H441 monolayers, remained unchanged. Western blot analysis of H441 cell lysates demonstrated reductions in alpha- but not gamma-ENaC subunit protein levels at 24 hours after RSV infection. The reduction in amiloride-sensitive I(sc) in H441 cells was prevented by pretreatment with inhibitors of de novo pyrimidine or purine synthesis (A77-1726 and 6-MP, respectively, 50 microM). Our results suggest that infection of both murine and human respiratory epithelial cells with RSV inhibits vectorial Na+ transport via nucleotide release. These findings are consistent with our previous studies showing reduced alveolar fluid clearance after RSV infection of BALB/c mice.

Mucosal inoculation with an attenuated mouse pneumovirus strain protects against virulent challenge in wild type and interferon-gamma receptor deficient mice

Protective mechanisms underlying the responses to mucosal vaccination are not yet clearly defined. Using the natural mouse pneumovirus pathogen, pneumonia virus of mice (PVM), we explore responses of wild type and interferon-gamma (IFNgamma) receptor gene-deleted mice to virulent challenge after mucosal vaccination with an attenuated virus strain. Serum neutralizing antibodies develop after intranasal inoculation with 30 pfu of attenuated, replication-competent PVM strain 15, which correlate with diminished gross and microscopic pulmonary pathology and protection from weight loss in response to subsequent challenge with the virulent parent PVM strain J3666. Virus replication in response to challenge was blunted in PVM strain 15 vaccinated mice, as was local production of secretory mediators IFNgamma, TNF-alpha, MIP-1 alpha, and MIP-2. Interestingly, responses of vaccinated IFNgamma receptor gene-deleted mice were indistinguishable from those of the wild type, suggesting that IFNgamma signaling may not be crucial for the generation of adaptive responses to pneumovirus infection in vivo.

The current state of infection with respiratory syncytial virus in the setting of congenital cardiac malformations

A long with prematurity and chronic lung disease, the presence of congenital cardiac disease in infants and young children is a significant risk for the clinical consequences of an illness produced by infection with the respiratory syncytial virus.1In this review, we present a current understanding of such illnesses, their prevention, and their treatment.

Inhibition of respiratory syncytial virus in cultured cells by nucleocapsid gene targeted deoxyribozyme (DNAzyme)

Respiratory syncytial virus (RSV), which presents the primary cause of bronchiolitis and pneumonia among infants and causes significant morbidity and mortality in immunodeficient patients, remains a health problem worldwide. Unfortunately, an effective vaccine is currently unavailable and pharmacologic treatment needs further optimization for RSV disease. Because RSV is a non-segmented negative-strand RNA virus, it may be sensitive to the genome RNA cleaving by DNAzyme, an artificial nucleic acids molecule with high catalytic capability of cleaving complementary RNA molecules. Thus, RSV-targeted DNAzymes potentially present as a therapeutic candidate of RSV diseases. In this study, DNAzymes targeting the RSV genomic RNA or mRNA were designed and synthesized, one of which (DZn1133) did cleave RSV RNA in vitro, inhibit the transcription and expression of F viral gene, reduce the RSV yield by about 7 logs and protect more than 90% RSV-infected Hep-2 cells from a cytopathic effect at 8 microM. Moreover, 10 wild RSV strains isolated from clinic patients including both subgroups A and B were all suppressed by DZn1133 with greater anti-RSV activity than antisense DNA or ribavirin.

Airway infectious disease emergencies

Upper and lower respiratory infections are encountered commonly in the emergency department. Visits resulting from occurrences of respiratory disease account for 10% of all pediatric emergency department visits and 20% of all pediatric hospital admissions. Causes of upper airway infections include croup, epiglottitis, retropharyngeal abscess, cellulitis, pharyngitis, and peritonsillar abscesses. Lower airway viral and bacterial infections cause illnesses such as pneumonia and bronchiolitis. Signs and symptoms of upper and lower airway infections overlap, but the differentiation is important for appropriate treatment of these conditions. This article reviews the varied clinical characteristics of upper and lower airway infections.

The impact of severe respiratory syncytial virus on the child, caregiver, and family during hospitalization and recovery

OBJECTIVE

To quantify the magnitude of child, caregiver, and family distress associated with hospitalization for severe respiratory syncytial virus (RSV) and the posthospitalization recovery period.

DESIGN

A prospective study of 46 RSV-hospitalized infants and children < or =30 months of age with a history of prematurity (gestational age of < or =35 weeks) and 45 age-matched control subjects was performed. RSV group data were gathered during hospitalization and on days 4, 14, 21, and 60 after discharge; control group data were collected at the end of the RSV season and 60 days thereafter.

MAIN OUTCOME MEASURES

RSV severity; caregiver's rating of the child's health (100-point rating) and functional status (Functional Status IIR); caregiver health, stress (7-point rating), and anxiety (Spielberger State Anxiety Inventory); and family health and functioning (Family Adaptability and Cohesion Evaluation Scale II) were recorded.

RESULTS

The mean age of the sample was 10.2 months; 51% of the subjects were male. The average duration of hospital stay for the RSV group was 5.8 +/- 8 days. Most patients received supplemental oxygen (76%) and were monitored for apnea (60%). The mean age of the caregivers (93% mothers) was 29 years. During hospitalization, the RSV-infected patients' health and functional status were significantly poorer than those of control subjects. Caregivers of RSV-infected children reported more stress, greater anxiety, poorer health, and poorer family health and functioning. As long as 60 days after discharge, caregivers of RSV-infected children reported the children's health as significantly poorer and were personally more anxious, compared with control subjects.

CONCLUSIONS

RSV-related hospitalization creates significant distress for infants and children, caregivers, and families, with some effects extending as long as 60 days after discharge.

Respiratory syncytial virus: old challenges and new approaches

Better therapies and prevention strategies are needed to decrease the burden of acute RSV disease in all age populations worldwide. Furthermore, we can hypothesize that those improved measures also would likely have an effect on the chronic consequences of RSV infection in children and will reduce the incidence of recurrent wheezing and persistent pulmonary function abnormalities caused by RSV LRIs.

Driscoll Children's Hospital respiratory syncytial virus database: risk factors, treatment and hospital course in 3308 infants and young children, 1991 to 2002

BACKGROUND

Treatment of respiratory syncytial virus (RSV) lower respiratory tract infection has historically been one of the most frequent reasons for admission to Driscoll Children's Hospital.

OBJECTIVE

The objective of this study was to examine the relationship of risk factors for a severe and complicated disease course to the treatment and hospital length of stay.

METHODS

Subjects were identified through a retrospective review of the medical records of all patients discharged with a diagnosis of RSV lower respiratory tract infection during 9 of the 11 RSV seasons between July 1, 1991 and June 30, 2002. The RSV seasons from 1991-1992 to 1994-1995 were compared with the RSV seasons from 1995-1996 to 2001-2002 with regard to treatment and hospital course.

RESULTS

There were a total of 3308 admissions. Compared with patients with no risk factors, higher percentages of patients with age <6 weeks, history of prematurity, congenital heart disease and neurologic disease were admitted to the pediatric intensive care unit (PICU) and required mechanical ventilation (P < 0.001). Also the hospital length of stay was longer for patients with each of these individual risk factors (P < 0.001). The hospital length of stay and the percentages of patients admitted to the PICU and requiring on mechanical ventilation increased as the number of risk factors increased from zero to 3 or more (P < 0.001). Of patients with 3 or more risk factors, the average hospital length of stay was 13.5 days; 67% were admitted to the PICU, and 47% required mechanical ventilation. Ribavirin use decreased in patients with each of the individual risk factors (P < 0.001) as well as in patients with one or more risk factors (P < 0.001). At the same time the PICU admission rate increased from 6.1% to 11.2% (P < 0.001).

CONCLUSIONS

Patients with three or more risk factors were at very high risk for having a severe or complicated disease course associated with admission to the PICU, placement on mechanical ventilation and a longer hospital length of stay.

Animal pneumoviruses: molecular genetics and pathogenesis

Pneumoviruses are single-stranded, negative-sense, nonsegmented RNA viruses of the family Paramyxoviridae, subfamily Pneumovirinae, and include pathogens that infect humans (respiratory syncytial virus and human metapneumovirus), domestic mammals (bovine, ovine, and caprine respiratory syncytial viruses), rodents (pneumonia virus of mice), and birds (avian metapneumovirus). Among the topics considered in this review are recent studies focused on the roles of the individual virus-encoded components in promoting virus replication as well as in altering and evading innate antiviral host defenses. Advances in the molecular technology of pneumoviruses and the emergence of recombinant pneumoviruses that are leading to improved virus-based vaccine formulations are also discussed. Since pneumovirus infection in natural hosts is associated with a profound inflammatory response that persists despite adequate antiviral therapy, we also review the recent experimental treatment strategies that have focused on combined antiviral, anti-inflammatory, and immunomodulatory approaches.

[Treatment for viral respiratory infections: Principles of action, strategies, and future prospects]

Pulmonary viral infections are associated with substantial morbidity and socioeconomic costs. Rhinovirus, influenza A and B, adenovirus, parainfluenza, respiratory syncytial virus (RSV), and coronavirus are etiologies most often associated with infections of the upper and lower respiratory tract. Therapy of viral infections in nonimmunocompromised hosts has only developed slowly during recent years, despite the enormous socioeconomic impact. This is in part due to the complex virus/host interactions and numerous and varying mechanisms of infection. Neuraminidase inhibitors have produced notable progress in the therapeutic approaches to influenza-associated pulmonary infections and are at least able to shorten the duration of symptoms in selected patients. However, neuraminidase inhibitors can only be applied in specific infections and the spectrum of agents with antiviral activity is broad. This article summarizes major principles of antiviral efficacy and reviews recent clinical trials.

Treatment of respiratory syncytial virus: antiviral therapies

Treatment of respiratory syncytial virus (RSV) in infants with bronchiolitis is complicated because of the multifactorial nature of this infection. The signs and symptoms of RSV result from a combination of direct viral cytopathic effects, host inflammatory responses that lead to airway obstruction and bronchoconstriction. It is logical that therapies targeting just one of these processes might be minimally effective, at best. Thus an important goal is to identify patients at risk and intervene to prevent disease, whenever possible. Once disease has been identified, the clinician must decide whether antiviral therapy is appropriate. Familiarity with typical viral load dynamics during the course of a lower respiratory tract infection can assist in the therapeutic decision process. For example in a patient who has had airway obstruction and other respiratory symptoms for >3 days, viral load has already peaked. Clearly this pattern has important implications for antiviral therapies.Preventive strategies include educating parents and family about hand washing, cleaning environmental surfaces, isolating infants and children with infection and avoiding crowded places such as busy day-care centers. High risk patients, who meet the American Academy of Pediatrics criteria for RSV prophylaxis, may be candidates for passive prophylaxis.

Bronchiolitis management preferences and the influence of pulse oximetry and respiratory rate on the decision to admit

OBJECTIVE

High incidence, rising admission rates, and relatively ineffective therapies make the management of bronchiolitis controversial. Since 1980, the rate of hospitalization for children with bronchiolitis has increased by nearly 250%, whereas mortality rates for the disease have remained constant. It has been speculated that the increasing use of pulse oximetry has lowered the threshold for admission and may have contributed to the rise in bronchiolitis-related admissions. The objective of this study was to describe pediatric emergency medicine physicians' management preferences regarding infants with moderately severe bronchiolitis and to assess the influence of specific differences in oxygen saturation as measured by pulse oximetry (SpO2) and respiratory rate (RR) on the decision to admit.

METHODS

Physicians who are members of the American Academy of Pediatrics Section of Emergency Medicine and living in the United States were randomized into 4 groups and mailed a survey that contained 1 of 4 vignettes. Vignettes were identical except for given SpO2 values (94% or 92%) and RR (50/min or 65/min). Subjects were asked to answer questions regarding laboratory tests, treatment options, and the decision to admit for the patient in their vignette.

RESULTS

We received completed surveys from 519 (64%) of the 812 physicians contacted. Most respondents recommended use of bronchodilators (96%), nasal suction (82%), and supplemental oxygen (57%). Few respondents recommended decongestants (9%), steroids (8%), or antibiotics (2%). When asked to rank therapies, respondents gave nasal suction 182 number 1 votes; bronchodilators received 164. The decision to admit varied with SpO2 and RR. Forty-three percent of respondents who received a vignette featuring SpO2 of 94% and a RR of 50/min recommended admission for the infant in their vignette. Fifty-eight percent recommended admission when the vignette SpO2 was 94% and RR was 65/min (chi2 = 5.021). Respondents who received a vignette with SpO2 of 92% were nearly twice as likely to recommend admission: 83% recommended admission when vignette RR was 50/min, and 85% recommended admission when vignette RR was 65/min (chi2 = 0.126).

CONCLUSIONS

When treating infants with moderately severe bronchiolitis, pediatricians who work in emergency departments frequently use bronchodilators and nasal suction, 2 practices for which supporting data are either conflicting (bronchodilators) or nonexistent (nasal suction). In addition, their decisions to admit differ markedly on the basis of only a 2% difference in SpO2. It is possible that increased reliance on pulse oximetry has contributed to the increase in bronchiolitis hospitalization rates seen during the past 2 decades.

Passive smoking, as measured by hair nicotine, and severity of acute lower respiratory illnesses among children

The aim of this study was to describe the association between passive smoking and the severity of acute lower respiratory illnesses (ALRI) among 351 children aged 3–27 months admitted to hospital. A total of 297 children provided hair samples, which were analysed for hair nicotine levels as an indicator of passive smoking. A severity of illness grading system was developed by using clinical and management criteria used by the medical staff at hospital. The OR for children with more severe illness being exposed to higher nicotine levels was 1.2, 95% CI: 0.57–2.58 when using dichotomised respiratory severity levels and upper versus lower nicotine quartile levels. In an ordinal logistic regression model, the OR of more severe illness being associated with higher nicotine levels was 1.07 (95% CI: 0.92–1.25). When analysis was limited to the more severe cases, the OR of the least severe category compared to the most severe category, in relation to nicotine levels in hair, was 1.79 (95% CI: 0.5–6.30). The ordinal logistic regression of this group of severely-ill children (OR 1.1 (95% CI: 0.94–1.29) was not substantially different from the overall study subjects.

In general, children with more severe illness tended to have higher levels of nicotine in their hair, although the results were within the limit of chance. Possible explanations of our results include environmental tobacco smoke (ETS) being an initiator of ALRI rather than a risk to severity, exposure levels of ETS were too low to demonstrate an effect on severity, or the power of this study was not high enough to detect an association.

Respiratory Viruses

Acute respiratory disease, including the common cold, influenza-like illness, croup, bronchiolitis, and viral pneumonia, can be caused by a wide variety of viral and non-viral agents. Among the viruses, those with RNA genomes tend to play a more prominent role, particularly among immunologically intact individuals. DNA viruses are also associated with respiratory disease. The characteristics of the viruses most often associated with respiratory disease are described briefly in the chapter. Three distinct types of influenza viruses are recognized, influenza A virus, influenza B virus, and influenza C virus, based on antigenic differences in the nucleoprotein and matrix proteins. All three viruses share certain characteristics, including the presence of a viral envelope containing glycoproteins important for viral entry and egress from cells, and a segmented genome. The standard nomenclature for influenza viruses includes the influenza type, place of initial isolation, strain designation, and year of isolation.