Ribavirin aerosol for acute bronchiolitis

Impact of Respiratory Syncytial Virus Infection on Host Functions: Implications for Antiviral Strategies

Respiratory syncytial virus (RSV) is one of the leading causes of viral respiratory tract infection in infants, the elderly, and the immunocompromised worldwide, causing more deaths each year than influenza. Years of research into RSV since its discovery over 60 yr ago have elucidated detailed mechanisms of the host-pathogen interface. RSV infection elicits widespread transcriptomic and proteomic changes, which both mediate the host innate and adaptive immune responses to infection, and reflect RSV's ability to circumvent the host stress responses, including stress granule formation, endoplasmic reticulum stress, oxidative stress, and programmed cell death. The combination of these events can severely impact on human lungs, resulting in airway remodeling and pathophysiology. The RSV membrane envelope glycoproteins (fusion F and attachment G), matrix (M) and nonstructural (NS) 1 and 2 proteins play key roles in modulating host cell functions to promote the infectious cycle. This review presents a comprehensive overview of how RSV impacts the host response to infection and how detailed knowledge of the mechanisms thereof can inform the development of new approaches to develop RSV vaccines and therapeutics.

Challenges and opportunities in developing respiratory syncytial virus therapeutics

Two meetings, one sponsored by the Wellcome Trust in 2012 and the other by the Global Virology Foundation in 2013, assembled academic, public health and pharmaceutical industry experts to assess the challenges and opportunities for developing antivirals for the treatment of respiratory syncytial virus (RSV) infections. The practicalities of clinical trials and establishing reliable outcome measures in different target groups were discussed in the context of the regulatory pathways that could accelerate the translation of promising compounds into licensed agents. RSV drug development is hampered by the perceptions of a relatively small and fragmented market that may discourage major pharmaceutical company investment. Conversely, the public health need is far too large for RSV to be designated an orphan or neglected disease. Recent advances in understanding RSV epidemiology, improved point-of-care diagnostics, and identification of candidate antiviral drugs argue that the major obstacles to drug development can and will be overcome. Further progress will depend on studies of disease pathogenesis and knowledge provided from controlled clinical trials of these new therapeutic agents. The use of combinations of inhibitors that have different mechanisms of action may be necessary to increase antiviral potency and reduce the risk of resistance emergence.

Viral infections of the respiratory tract: prevention and treatment

The rapid discovery of specific viral agents as the cause of many acute respiratory diseases was accompanied by considerable optimism that vaccines or other control measures could be developed quickly. Subsequent experience has demonstrated that effective control of these important public health problems has been an elusive goal. However, recent exciting developments in our understanding of the molecular biology and immunology of these viruses may provide the basis for more effective strategies in the future.

WITHDRAWN: Ribavirin for respiratory syncytial virus infection of the lower respiratory tract in infants and young children

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract infection in infants and is responsible for many hospitalizations annually. Ribavirin is approved for treatment of these infections, but its use is controversial because of questions about its efficacy, concerns about occupational exposure, and its high cost.

OBJECTIVES

The objective of this review is to assess the efficacy of aerosolized ribavirin for infants and children with lower respiratory tract infection due to RSV.

SEARCH STRATEGY

We performed an updated electronic search of the Cochrane Central Register of Controlled Trials (CENTRAL), the Database of Abstracts of Reviews of Effects (DARE) and the NHS Economic Evaluation Database (EED) (The Cochrane Library 2006, issue 3) which contains the Acute Respiratory Infections Group's specialized register; MEDLINE (Ovid) (2004 to September Week 3 2006); and EMBASE (WebSpirs) (2004 to June 2006).

SELECTION CRITERIA

Randomized trials comparing ribavirin with placebo in infants and children with lower respiratory tract infection attributable to RSV.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality. Unpublished data were requested from trial authors when necessary.

MAIN RESULTS

Twelve trials were included. All trials enrolled infants below the age of six months. In four trials with 158 participants, mortality with ribavirin was 5.8% compared with 9.7% with placebo (odds ratio (OR) 0.58; 95% confidence interval (CI) 0.18 to 1.85). In three trials with 116 participants the probability of respiratory deterioration with ribavirin was 7.1% compared with 18.3% with placebo (OR 0.37; 95% CI 0.12 to 1.18). In three studies with 104 ventilated participants, the mean difference in days of hospitalization was 1.9 fewer days with ribavirin (95% CI -4.6 to +0.9) and the mean difference in days of ventilation was 1.8 fewer days with ribavirin (95% CI -3.4 to -0.2). No statistically significant differences in long-term pulmonary function or in incidence of recurrent wheezing following RSV infection were associated with the use of ribavirin.

AUTHORS' CONCLUSIONS

Trials of ribavirin for RSV lack sufficient power to provide reliable estimates of the effects. The cumulative results of three small trials show that ribavirin may reduce the duration of mechanical ventilation and may reduce days of hospitalization. In addition, use of ribavirin may be associated with a decrease in the long-term incidence of recurrent wheezing following RSV disease. A large randomized controlled trial of ribavirin for ventilated and other high-risk participants is indicated.

Respiratory syncytial virus infections: characteristics and treatment

In this review, we describe the history, epidemiology and clinical manifestations of infections attributed to respiratory syncytial virus (RSV) in children. At present, no cure exists for RSV infection but commonly employed palliative treatments include oxygen and inhaled β2-adrenoceptor agonists, such as salbutamol, to relieve the wheezing and increased bronchiolar smooth muscle constriction. Adrenaline (epinephrine) has been found to be superior to the selective β2-adrenoceptor agonists. Oral or inhaled corticosteroids should counteract the inflammatory response to RSV infection but their effectiveness is controversial. Inhaled ribavirin is the only licensed antiviral product approved for the treatment of RSV lower respiratory-tract infection in hospitalized children, although its use is now restricted to high-risk infants. Other treatments considered are nasopharyngeal suctioning, surfactant therapy, recombinant human deoxyribonuclease I, heliox (helium:oxygen) and inhaled nitric oxide. Prevention of infection by RSV antibodies is another strategy and, currently, palivizumab is the only safe, effective and convenient preventative treatment for RSV disease in high-risk populations of infants and young children. Its cost-effectiveness, however, has been questioned. Both live attenuated and subunit vaccines against RSV infection have been developed but so far there is no safe and effective vaccine available. Finding effective treatments and prophylactic measures remains a major challenge for the future.

Cough and viruses in airways disease: mechanisms

Acute cough is a major symptom of viral respiratory tract infection and causes excessive morbidity in human populations across the world. A wide variety of viruses play a role in the development of cough after acute infection and all of these manifest a similar clinical picture across different age groups. Despite the large disease burden surprisingly little is known about the mechanism of acute cough following viral infection. Both in vitro and in vivo experiments show that increased production of neuropeptides and leukotrienes mediate cough after viral infection, along with altered expression of neural receptors. Increased airway mucus production is also likely to play a significant role. This work is reviewed in this article.

Following the recent development of a mouse model for rhinovirus infection and the establishment of experimental models of rhinovirus challenge in human subjects with both asthma and COPD the field is expanding to translate in vitro research into clinical studies and hopefully eventually into clinical practice. Developing a clearer understanding of the mechanisms underlying virus induced cough may lead to more specific and effective therapies.

Risk factors for respiratory syncytial virus bronchiolitis hospital admission in New Zealand

This study assessed risk factors for respiratory syncytial virus (RSV) hospitalization and disease severity in Wellington, New Zealand. During the southern hemisphere winter months of 2003--2005, 230 infants aged < 24 months hospitalized with bronchiolitis were recruited. RSV was indentified in 141 (61%) infants. Comparison with data from all live hospital births from the same region (2003--2005) revealed three independent risk factors for RSV hospitalization: birth between February and July [adjusted risk ratio (aRR) 1.62, 95% confidence interval (CI) 1.5-2.29], gestation <37 weeks (aRR 2.29, 95% CI 1.48-3.56) and Māori ethnicity (aRR 3.64, 95% CI 2.27-5.85), or Pacific ethnicity (aRR 3.60, 95% CI 2.14-6.06). The high risk for Māori and Pacific infants was only partially accounted for by other known risk factors. This work highlights the importance of RSV disease in indigenous and minority populations, and identifies the need for further research to develop public health measures that can reduce health disparities.

Ribavirin for respiratory syncytial virus infection of the lower respiratory tract in infants and young children

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract infection in infants and is responsible for many hospitalizations annually. Ribavirin is approved for treatment of these infections, but its use is controversial because of questions about its efficacy, concerns about occupational exposure, and its high cost.

OBJECTIVES

The objective of this review is to assess the efficacy of aerosolized ribavirin for infants and children with lower respiratory tract infection due to RSV.

SEARCH STRATEGY

We performed an updated electronic search of the Cochrane Central Register of Controlled Trials (CENTRAL), the Database of Abstracts of Reviews of Effects (DARE) and the NHS Economic Evaluation Database (EED) (The Cochrane Library Issue 3, 2006); MEDLINE (Ovid) (2004 to September Week 3 2006); and EMBASE (WebSpirs) (2004 to June 2006).

SELECTION CRITERIA

Randomized trials comparing ribavirin with placebo in infants and children with lower respiratory tract infection attributable to RSV.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality. Unpublished data were requested from trial authors when necessary.

MAIN RESULTS

Twelve trials were included. All trials enrolled infants below the age of six months. In four trials with 158 participants, mortality with ribavirin was 5.8% compared with 9.7% with placebo (odds ratio (OR) 0.58; 95% confidence interval (CI) 0.18 to 1.85). In three trials with 116 participants the probability of respiratory deterioration with ribavirin was 7.1% compared with 18.3% with placebo (OR 0.37; 95% CI 0.12 to 1.18). In three studies with 104 ventilated participants, the mean difference in days of hospitalization was 1.9 fewer days with ribavirin (95% CI -4.6 to +0.9) and the mean difference in days of ventilation was 1.8 fewer days with ribavirin (95% CI -3.4 to -0.2). No statistically significant differences in long-term pulmonary function or in incidence of recurrent wheezing following RSV infection were associated with the use of ribavirin.

AUTHORS' CONCLUSIONS

Trials of ribavirin for RSV lack sufficient power to provide reliable estimates of the effects. The cumulative results of three small trials show that ribavirin may reduce the duration of mechanical ventilation and may reduce days of hospitalization. In addition, use of ribavirin may be associated with a decrease in the long-term incidence of recurrent wheezing following RSV disease. A large randomized controlled trial of ribavirin for ventilated and other high-risk participants is indicated.

Diagnosis and management of bronchiolitis

Bronchiolitis is a disorder most commonly caused in infants by viral lower respiratory tract infection. It is the most common lower respiratory infection in this age group. It is characterized by acute inflammation, edema, and necrosis of epithelial cells lining small airways, increased mucus production, and bronchospasm. The American Academy of Pediatrics convened a committee composed of primary care physicians and specialists in the fields of pulmonology, infectious disease, emergency medicine, epidemiology, and medical informatics. The committee partnered with the Agency for Healthcare Research and Quality and the RTI International-University of North Carolina Evidence-Based Practice Center to develop a comprehensive review of the evidence-based literature related to the diagnosis, management, and prevention of bronchiolitis. The resulting evidence report and other sources of data were used to formulate clinical practice guideline recommendations. This guideline addresses the diagnosis of bronchiolitis as well as various therapeutic interventions including bronchodilators, corticosteroids, antiviral and antibacterial agents, hydration, chest physiotherapy, and oxygen. Recommendations are made for prevention of respiratory syncytial virus infection with palivizumab and the control of nosocomial spread of infection. Decisions were made on the basis of a systematic grading of the quality of evidence and strength of recommendation. The clinical practice guideline underwent comprehensive peer review before it was approved by the American Academy of Pediatrics. This clinical practice guideline is not intended as a sole source of guidance in the management of children with bronchiolitis. Rather, it is intended to assist clinicians in decision-making. It is not intended to replace clinical judgment or establish a protocol for the care of all children with this condition. These recommendations may not provide the only appropriate approach to the management of children with bronchiolitis.

Respiratory syncytial virus infections: Recent prospects for control

Respiratory syncytial virus (RSV) infections remain a significant public health problem throughout the world, although recently developed and clinically approved anti-RSV antibodies administered prophylactically to at-risk populations appear to have significantly affected the disease development. Much effort has been expended to develop effective anti-RSV therapies, using both in vitro assay systems and mouse, cotton rat, and primate models, with several products now in various stages of clinical study. Several products are also being considered for the treatment of clinical symptoms of RSV. In this review, updates on the status of the approved anti-RSV antibodies, ribavirin, and recent results of studies with potential new anti-RSV compounds are summarized and discussed.

Advances in the treatment and prevention of severe viral bronchiolitis

Viral bronchiolitis continues to be a major public health problem. Prevention of severe RSV-associated bronchiolitis has been achieved in high-risk infants by passive administration of the humanized monoclonal anti-RSV-F antibody, palivizumab. Development of more potent anti-RSV neutralizing antibodies is underway, and vaccine development continues to progress. Supportive therapy is the mainstay for the treatment of established infection while new antiviral and anti-inflammatory strategies are being explored in preclinical trials.

Ribavirin for respiratory syncytial virus infection of the lower respiratory tract in infants and young children

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract infection in infants and is responsible for 100,000 hospitalizations annually. Ribavirin is approved for treatment of these infections, but its use is controversial because of questions about its efficacy, concerns about occupational exposure, and its high cost.

OBJECTIVES

The objective of this review is to assess the efficacy of aerosolized ribavirin for infants and children with lower respiratory tract infection due to RSV.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1, 2004), MEDLINE (January 1975 to January week 3, 2004) and EMBASE (January 1990 to December 2003). We scanned reference lists of articles and contacted experts in the field.

SELECTION CRITERIA

Randomized trials comparing ribavirin with placebo in infants and children with RSV infection and lower respiratory tract infection.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality. Unpublished data were requested from authors when necessary.

MAIN RESULTS

Twelve trials were included. All trials enrolled infants below the age of six months. In four trials with 158 patients, mortality with ribavirin was 5.8% compared with 9.7% with placebo (odds ratio (OR) 0.58; 95% confidence interval (CI) 0.18 to 1.85). In three trials with 116 patients the probability of respiratory deterioration with ribavirin was 7.1% compared with 18.3% with placebo (OR 0.37; 95% CI 0.12 to 1.18). In three studies with 104 ventilated patients, the weighted mean difference in days of hospitalization was 1.9 fewer days with ribavirin (95% CI -4.6 to +0.9) and the weighted mean difference in days of ventilation was 1.8 fewer days with ribavirin (95% CI -3.4 to -0.2). No statistically significant differences in long-term pulmonary function or in incidence of recurrent wheezing following RSV infection were associated with the use of ribavirin.

REVIEWERS' CONCLUSIONS

Trials of ribavirin for RSV lack sufficient power to provide reliable estimates of the effects. The cumulative results of three small trials show that ribavirin may reduce the duration of mechanical ventilation and may reduce days of hospitalization. In addition, use of ribavirin may be associated with a decrease in the long-term incidence of recurrent wheezing following RSV disease. A large randomized controlled trial of ribavirin for ventilated and other high-risk patients is indicated.

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.

Current treatment for acute viral bronchiolitis in infants

This paper provides an update and critical review of available data on the treatment of acute viral bronchiolitis in previously healthy infants, with special focus on new or promising therapies. The main potential benefits of medical assistance in these patients reside in the careful monitoring of their clinical status, the maintenance of adequate hydration and oxygenation, the preservation of the airway opened and cleared of secretions and the option to perform parental education. There is no convincing evidence that any other form of therapy will reliably provide beneficial effects in infants with bronchiolitis and currently, any treatment beyond supportive care should be prescribed on a case-by-case basis with watchful appraisal of its effects. Therapies such as ribavirin, IFN, vitamin A, antibiotics, mist therapy or anticholinergics, have not demonstrated any measurable clinical effect. Several studies and meta-analyses with beta(2)-agonists and corticosteroids have failed to show any benefit of significant extent, however, physicians keep favouring their use. Presently, adrenaline has received rather consistent support from clinical trials but it is not yet widely prescribed. There are other therapeutic strategies, for instance, heliox, hypertonic saline, noninvasive ventilation, physical therapy techniques, thickened feeds or palivizumab that have shown promising potential benefits, but evidence supporting its use is still limited and further studies should be warranted. In the meantime, infants with acute viral bronchiolitis should be treated following evidence-based clinical practice guidelines, keeping the patient central in the process and being sensitive to social, cultural and familiar influences on their treatment strategy.

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.

Systemic corticosteroids in infant bronchiolitis: A meta-analysis

OBJECTIVE

To determine whether corticosteroids are efficacious in treating bronchiolitis in hospitalized infants.

METHODS

Online bibliographic databases (Medline, Embase, and Cochrane Clinical Trials Registry) were searched for: 1) bronchiolitis or respiratory syncytial virus, and 2) corticosteroid or glucocorticoid or steroidal antiinflammatory agents or adrenal cortex hormones. Reference lists from all selected articles were also examined. Randomized, placebo-controlled trials of systemic corticosteroids in treatment of infants hospitalized with bronchiolitis were selected by 2 investigators. Of 12 relevant publications identified in the literature search, 6 met the selection criteria and had relevant data available. Investigators independently extracted data for 3 outcomes: length of stay (LOS), duration of symptoms (DOS), and clinical scores.

RESULTS

In the pooled analysis, infants who received corticosteroids had a mean LOS or DOS that was.43 days less than those who received the placebo treatment (95% confidence interval: -.81 to -.05 days). The effect size for mean clinical score was -1.60 (95% confidence interval: -1.92 to -1.28), favoring treatment. Secondary analyses of mean LOS or DOS were performed on 5 trials that had clearly identified methods of randomization, 5 trials that measured LOS, and 4 trials that clearly excluded infants with previous wheezing. The estimates of effect were similar to the primary analysis but were not statistically significant.

CONCLUSIONS

Combined, published reports of the effect of systemic corticosteroids on the course of bronchiolitis suggest a statistically significant improvement in clinical symptoms, LOS, and DOS.

Association of fever and severe clinical course in bronchiolitis

Little attention has been given to the relation between fever and the severity of bronchiolitis. Therefore, the relation between fever and the clinical course of 90 infants (59 boys, 31 girls) hospitalised during one season with bronchiolitis was studied prospectively. Fever (defined as a single recording > 38.0 degrees C or two successive recording > 37.8 degrees C) was present in 28 infants. These infants were older (mean age, 5.3 v 4.0 months), had a longer mean hospital stay (4.2 v 2.7 days), and a more severe clinical course (71.0% v 29.0%) than those infants without fever. Radiological abnormalities (collapse/consolidation) were found in 60. 7% of the febrile group compared with 14.8% of the afebrile infants. These results suggest that monitoring of body temperature is important in bronchiolitis and that fever is likely to be associated with a more severe clinical course and radiological abnormalities.

Ribavirin in ventilated respiratory syncytial virus bronchiolitis. A randomized, placebo-controlled trial

We undertook a prospective, double-blind, placebo-controlled trial to resolve the question of the clinical effectiveness of ribavirin in previously well infants who require ventilation for respiratory distress secondary to respiratory syncytial virus (RSV) bronchiolitis. Aerosol ribavirin or NaCl 0.9% was administered within 24 h of initiation of ventilation, 18 h/d, for a maximum of 7 d or until extubation. From March 1994 to March 1997, 42 children were randomized and 41 patients were retained for analysis. Baseline characteristics of each group-ribavirin and placebo (20:21)-were not significantly different with respect to age (62.5 +/- 35.9 versus 62.7 +/- 30.9 d), sex, weight, and length of ventilation pre-aerosol. "Intent to treat" outcome analysis found no significant differences in the length of the following: ventilation (102.16 +/- 65.26 versus 126.28 +/- 78.72 h; p = 0.29), aerosol therapy, stay in the intensive care unit, total oxygen therapy, and hospitalization. The aerosols were well tolerated and no deaths occurred. This trial demonstrates the lack of effectiveness of aerosolized ribavirin in reducing the length of ventilation and course of illness in infants with no underlying illness ventilated for respiratory distress secondary to RSV bronchiolitis.

Respiratory syncytial virus infection: immune response, immunopathogenesis, and treatment

Respiratory syncytial virus (RSV) is the single most important cause of lower respiratory tract infection during infancy and early childhood. Once RSV infection is established, the host immune response includes the production of virus-neutralizing antibodies and T-cell-specific immunity. The humoral immune response normally results in the development of anti-RSV neutralizing-antibody titers, but these are often suboptimal during an infant's initial infection. Even when the production of RSV neutralizing antibody following RSV infection is robust, humoral immunity wanes over time. Reinfection during subsequent seasons is common. The cellular immune response to RSV infection is also important for the clearance of virus. This immune response, vital for host defense against RSV, is also implicated in the immunopathogenesis of severe lower respiratory tract RSV bronchiolitis. Many details of the immunology and immunopathologic mechanisms of RSV disease known at present have been learned from rodent models of RSV disease and are discussed in some detail. In addition, the roles of immunoglobulin E, histamine, and eosinophils in the immunopathogenesis of RSV disease are considered. Although the treatment of RSV bronchiolitis is primarily supportive, the role of ribavirin is briefly discussed. Novel approaches to the development of new antiviral drugs with promising anti-RSV activity in vitro are also described.

Severity of illness models for respiratory syncytial virus-associated hospitalization

The objective of this investigation was to examine the feasibility of multivariate severity of illness models for pediatric patients hospitalized with respiratory syncytial virus (RSV) infection. From a preexisting retrospective cohort study database, all infants and children 2 yr of age or younger with community-acquired RSV infection admitted to the University of Michigan's C. S. Mott Children's Hospital during nine epidemics were examined. The study group consisted of 802 hospitalized patients younger than 2 yr of age with community-acquired RSV infection; 182 (23%) patients had prolonged hospital length of stay defined as 7 d or greater. Multivariate logistic regression modeling of nine variables measurable during the first hospital day was strongly associated with prolonged hospitalization (p < 0.0001). Receiver operator characteristic curve analysis resulted in an area under the curve of 0.894, indicating excellent model discrimination. Goodness-of-fit testing indicated excellent model calibration for observed versus predicted outcomes (p = 0.216). We conclude that severity of illness models for RSV-associated hospitalization with excellent predictive properties in terms of classification, discrimination, and calibration are possible. Further study is required to determine if such models are generalizable across multiple centers and epidemics.

Respiratory syncytial virus (RSV) disease and prospects for its control

Respiratory syncytial virus (RSV) is a major virus pathogen of infants and young children, an important cause of disease in adults and is responsible for a significant amount of excess morbidity and mortality in the elderly. It also can be devastating in immunosuppressed populations. Vaccines are being developed, but none are currently licensed. Moreover, even if one or more are approved, they may not be suitable for some populations vulnerable to RSV (e.g. very young infants and the immunosuppressed). Ribavirin and immunoglobulin preparations with high titers of RSV-specific neutralizing antibodies are currently approved for use to treat and prevent RSV infection. However, neither of these is cost-effective or simple to administer. New agents are needed to reduce the impact of RSV. This review is concerned with the means currently available for controlling RSV, the search for new agents effective against this virus, and future prospects for preventing and treating RSV infections.

[Is the use of ribavirin aerosols in respiratory syncytial virus infections justified? Clinical and economic evaluation]

The controversy about the use of ribavirin aerosol for children at risk (cardiopathy, pneumopathy, premature and immunodeficient patients), in case of respiratory syncytial virus (RSV) infection, led us to stop its prescription in 1993 and study prospectively the patients admitted during the following winters.

METHODS

Criterias of inclusion for this study were those of the Committee on Infectious Diseases of the American Academy of Pediatrics concerning the use of ribavirin aerosol. Two cohorts of patients were studied: the first group included treated patients (ribavirin group: n = 22, ribavirin and support treatment: salbutamol aerosols, respiratory physiotherapy and oxygen-therapy; winters 1989-1990 to 1992-1993); the second group included patients with support treatment only (control group: n = 22; winters 1993-1994 and 1994-1995).

RESULTS

The clinical gravity score at admission (4.55 vs 5.23, P = 0.46) and the risk factor scores (3.05 vs 3.27, P = 0.69) of the two groups were identical. Results showed that the children of the ribavirin group stayed much longer in hospital (14.2 vs 8.2 days, P = 0.002) and in the intensive care unit (7.2 vs 0.2 days, P < 0.001) than those of the control group. More support treatment was necessary for the ribavirin group as regard respiratory physiotherapy (3.8 vs 2.7 sessions a day, P = 0.026), the duration of oxygen-therapy (7.3 vs 3.7 days, P = 0.030) and the number of children requiring respiratory assistance (4 vs 0 children, P = 0.116). Administration of ribavirin aerosols (480 US$ a dose) and the way in which such treatment was carried out meant high daily costs for the ribavirin group (1,076 vs 604 US$, P < 0.001). As hospitalization was longer for children treated with ribavirin, the global cost was therefore much higher (15,552 vs 5,156 US$, P < 0.001).

CONCLUSION

The antiviral effect of ribavirin is undeniable. However ribavirin is known to be the cause of severe bronchospasms (two cases in our study) and can also cause moderate and long term bronchospasms, aggravating therefore the clinical evolution of the disease. Our experience shows that administration of ribavirin aerosols in case of RSV infection of inferior respiratory airways seems not to be justified.

Prevention and treatment recommendations for respiratory syncytial virus infection. Background and clinical experience 40 years after discovery

Though 40 years have passed since its discovery, respiratory syncytial virus (RSV), one of the most ubiquitous viruses known, continues to evade most of our efforts to prevent or treat the clinical disease it causes. Long recognised as the most common cause of lower respiratory tract infections in virtually all children in the first 2 years of life, it has been increasingly recognised as a cause of more serious disease in several 'high risk' populations. These populations include infants with cardiac or pulmonary disease and infants and adults with immunodeficiencies, particularly those undergoing bone marrow transplantation. Early attempts to immunise children with a simple formalin-inactivated vaccine led to severe disease in vaccinated children who subsequently were infected with RSV from the community. Other vaccine constructs have failed for a variety of reasons, although surface glycoprotein subunit vaccines may hold promise. For years, ribavirin, a synthetic nucleoside analogue administered by constant aerosol, has been felt by many to lead to more rapid improvement in clinical disease caused by RSV, but it is still unclear whether its benefits are truly significant. An intravenous immunoglobulin product prepared from donors screened for the presence of high titres of RSV neutralising antibody (known as RSVIG) appears to be well tolerated and relatively effective in protecting high-risk infants against serious RSV disease, although therapeutic use has proven less dramatic. At least one monoclonal antibody undergoing current testing may prove easier to use in similar immunoprophylactic use. Results on the use of corticosteroids as supportive therapy have not been conclusive. In short, RSV will continue to be a challenge for clinicians and researchers well into the next century.

Long term follow-up of children hospitalized with respiratory syncytial virus lower respiratory tract infection and randomly treated with ribavirin or placebo

PURPOSE

To determine the long term effects of ribavirin therapy in children hospitalized for respiratory syncytial virus (RSV) lower respiratory tract infection.

METHODS

Fifty-four of 60 children in randomized trials of ribavirin therapy were enrolled in a prospective follow-up study. Subjects were examined annually and had age-appropriate pulmonary function tests; interim histories were obtained from families and personal physicians.

RESULTS

Recurrent lower respiratory tract illness was reported at least once for 79% of the ribavirin and 73% of placebo group. In the first 5 years after RSV, 54% of the ribavirin group and 50% of the placebo group reported wheezing. There were no significant differences between the groups in annual rates, timing, or severity of recurrent lower respiratory tract illness. No significant differences in pulmonary function were detected by tests of oxygen saturation, peak expiratory flow and spirometry.

CONCLUSIONS

Children in the ribavirin treatment group did not have exacerbated respiratory symptoms compared with those in the control group, and their pulmonary function measurements were equal to those of the placebo-treated group, suggesting no long term adverse effect or benefit of ribavirin therapy.

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

OBJECTIVES

To determine the relationship between receipt of aerosolized ribavirin and the hospital course of high-risk infants and children with respiratory syncytial virus (RSV) lower respiratory infection (LRI).

METHODS

The 1993-1994 Pediatric Investigators Collaborative Network on Infections in Canada (PICNIC) RSV database consists of prospectively enrolled children with acute RSV LRI, admitted to nine Canadian pediatric tertiary care centers. After excluding cases with compromised immunity and/or nosocomial infection, subsets with any congenital heart disease (CHD), chronic lung disease (CLD), age </=6 weeks (INFANT), gestation </=36 weeks (PREM), or severe disease within 48 hours of admission as shown by an oxygen saturation </=90% or an FiO2 requirement of >.35 (EARLY HYPOXIA) were studied in two ways. First, each risk group subset was analyzed separately to assess the association between ribavirin receipt and measures of disease severity including duration of intensive care, mechanical ventilation, hypoxia and RSV-attributable hospital stay. Secondly, ribavirin was added as an independent variable to a previously described multiple regression model for RSV-attributable length of hospital stay and two mutually exclusive subsets were analyzed: 1) previously healthy patients with >/=1 of: INFANT, PREM, or EARLY HYPOXIA; 2) patients with CHD and/or CLD.

RESULTS

Between January 1993 and June 1994, 1425 community-acquired hospitalized cases of RSV LRI were entered into the RSV database. Among these 750 (52.6%) fit into one or more of the defined subsets including 97 CHD, 134 CLD, 213 INFANT, 211 PREM, and 463 EARLY HYPOXIA. The proportion ventilated in each group was 20.6%, 20.9%, 15.5%, 15.2%, and 13.3%, respectively. Across the subsets ribavirin use ranged from 36% to 57% of ventilated patients and 6% to 39% of nonventilated patients. For nonventilated patients in each subset the median RSV-attributable hospital length of stay (RSV-LOS) was 2 to 3 days longer for ribavirin recipients and the duration of hypoxia was significantly increased. Duration of intensive care unit (ICU) stay was also increased for all ribavirin-treated subgroups except those with CHD. In contrast, for ventilated patients, ribavirin therapy was not significantly associated with any of the outcome measures regardless of risk group. In the multiple regression model, ribavirin was significantly associated with a prolonged RSV-LOS both for children with CHD and/or CLD as well as for those whose only risk factors included INFANT, PREM, and/or EARLY HYPOXIA.

CONCLUSIONS

These data raise further doubts about the clinical effectiveness of ribavirin in infants and children with risk factors for severe disease. Selection bias, with ribavirin used for sicker children, may have influenced outcome. Nevertheless the long durations of hospitalization, ICU, ventilation, and oxygen supplementation in nonventilated ribavirin recipients stress the need for further randomized trials to assess its efficacy.

Study of interobserver reliability in clinical assessment of RSV lower respiratory illness: a Pediatric Investigators Collaborative Network for Infections in Canada (PICNIC) study

Randomized trials of ribavirin therapy have used clinical scores to assess illness severity. Little information on agreement for these findings between observers has been published. We decided to determine interobserver agreement for (1) a history for apnea or respiratory failure; (2) assessment of cyanosis, respiratory rate, retractions, and oximetry; and (3) determination of reason for hospitalization (requirement for medications, supportive care, underlying illness, poor home environment). At eight centers 137 RSV-infected patients were assessed by two observers blinded to the assessments by others with no interventions made between assessments. Observations were categorized, and agreement was summarized as percentage of observed agreement, Pearson correlation, or as a kappa statistic. Observed agreement for a history of either apnea or a respiratory arrest was at least 90% at all centers, with seven of the eight centers in total agreement. At all centers except one, the agreement on the reason why the patient remained in hospital was at least 80%. The observed agreement for assessing cyanosis was at least 94% at all eight centers. The correlation coefficient for respiratory rate varied from 0.42 to 0.97 across centers. The kappa values for agreement beyond chance for retractions varied from 0.05 to 1.00. The kappa values for oxygen saturation measures varied from 0.31 to 0.70. Although not statistically significant, there appeared to be more variation as the time between assessments increased. In conclusion, agreement for historical findings and assessment of cyanosis was high. However, there was wide variation in agreement in the other assessments. Training to ensure consistent and reproducible assessment by different examiners will be necessary if these findings are to be used as outcome variables in clinical trials.

Effectiveness of ribavirin in otherwise well infants with respiratory syncytial virus-associated respiratory failure. Pediatric Critical Study Group

OBJECTIVE

To examine ribavirin's effectiveness in otherwise well infants with respiratory syncytial virus (RSV)-associated respiratory failure.

DESIGN

Prospective multicenter cohort study.

SETTING

Pediatric critical care units affiliated with the Pediatric Critical Care Study Group; 38 centers from the United States and Canada participated.

PATIENTS

Infants with RSV-associated respiratory failure undergoing mechanical ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data collected included demographic information; dates of hospitalization, intensive care, and mechanical ventilation; all patient diagnoses; reason for tracheal intubation; dates of ribavirin use before and during mechanical ventilation; time in hours after intubation until ribavirin administration; Pediatric Risk of Mortality (PRISM) score; and outcome. A total of 439 patients received mechanical ventilation for RSV-associated respiratory failure; 223 were classified as previously well and met entry criteria. Ninety-one infants (41%) received ribavirin during mechanical ventilation. The PRISM scores during the initial 24 hours of intensive care and blood gas measurements before intubation were similar for patients who received ribavirin versus those who did not. Use of ribavirin during mechanical ventilation was associated with prolonged duration of mechanical ventilation (p < 0.01) in a multivariate model that controlled for patient age, gender, prematurity status, and use of ribavirin before intubation. Subgroup analysis of mechanical ventilation days for previously well patients was 5.0 +/- 4.2 in the no-ribavirin group versus 6.4 +/- 5.0 in the ribavirin group (p < 0.05) and for well premature infants was 6.3 +/- 4.9 in the no-ribavirin group versus 9.0 +/- 6.3 in the ribavirin group (p < 0.01). The mortality rates for the term and the premature groups were similar for treated and untreated patients.

CONCLUSIONS

Ribavirin administration during mechanical ventilation to previously well infants with RSV infection was not associated with reductions in either mortality rates or duration of mechanical ventilation. Additional clinical effectiveness studies are required to define specific groups in which the use of aerosolized ribavirin is indicated.

Aerosolized immunoglobulin treatment of respiratory syncytial virus infection in infants

BACKGROUND

Recent studies in animals with experimental respiratory syncytial virus (RSV) infection indicate that passive immunization by intranasal or intratracheal application of gamma-globulins (immunoglobulins) may be beneficial for treatment of infants with lower respiratory tract infection caused by RSV.

METHODS

We conducted a placebo-controlled, randomized multicenter study involving 68 infants with proven RSV infection admitted to 5 pediatric centers in Switzerland from November 1, 1992, through April 30, 1993. Treatment was carried out with aerosolized human IgG (Sandoglobulin) by assisted ventilation. On the day of hospital admission a single dose of 0.1 g of IgG per kg of body weight in a 5% solution or an identical amount of placebo, each delivered in 2 parts, was given.

RESULTS

The two groups did not differ substantially in their response to the aerosol received. The rate of improvement for symptoms of respiratory tract infection, oxygen requirement and length of hospital stay were comparable for both groups. There was a significant reduction (P < 0.05) in the frequency of apneic spells observed in the treatment group by Day 3 posttreatment. Aerosol therapy was generally well-tolerated in nonintubated infants, but some severe side effects (increased oxygen requirements in two patients, pneumothorax in one patient) were observed in two of three intubated and ventilated infants treated with IgG.

CONCLUSIONS

Aerosolized immunoglobulin in the dosage used had no substantial beneficial effect on RSV bronchiolitis. Despite these findings passive immunotherapy for treatment of RSV-induced lower respiratory tract infection deserves further evaluation before being discarded as ineffective.

Role of ECMO in the treatment of respiratory syncytial virus bronchiolitis: a collaborative report

AIM

To report the collaborative experience of extracorporeal membrane oxygenation (ECMO) in the treatment of respiratory syncytial virus (RSV) bronchiolitis between April 1989 and January 1995.

METHODS

The medical records of patients with confirmed RSV bronchiolitis referred to three centres (Leicester, Glasgow, and Great Ormond Street) were reviewed.

RESULTS

Twenty four infants were identified. Seventeen had been born prematurely (gestational range 23-40 weeks, median 30 weeks). Thirteen infants had been mechanically ventilated after birth and seven of these had evidence of bronchopulmonary dysplasia (BPD). The age of onset of RSV infection varied from three to 64 weeks (mean 17.4 weeks, median 12 weeks). Ventilation before ECMO ranged from one to 16 days and oxygenation indices at the time of referral ranged from 21-73 (mean 39). Ribavirin was used in eight of the 24 patients. Sixteen patients received venoarterial and eight veno-venous ECMO. ECMO hours ranged from 32-647 (median 196 hours). One infant died (survival rate 96%). Cranial ultrasound abnormalities were detected in three patients. However, at follow up only one of the 23 survivors had evidence of developmental delay.

CONCLUSION

A group of paediatric patients in whom ECMO can be of benefit has been identified. The use of ECMO should be considered when other means of support prove unsuccessful.

Antiviral therapy in neonatal chronic lung disease

Infants born prematurely who develop chronic lung disease frequently suffer acute respiratory deteriorations. In a randomized trial, we assessed if treatment of such relapses with the antiviral agent Ribavirin increased the speed of recovery and improved lung function at follow-up. During the acute deterioration and its treatment, respiratory rate and requirement for respiratory support were recorded. Once discharged from hospital, respiratory symptoms and admissions for chest-related illnesses were documented. Infants were recalled at 6 months of age for lung function measurements. Forty-four infants (23 given Ribavirin), median gestational age of 26 weeks, completed the trial and had lung function measurements at 6 months. Although viral infections were identified in relatively few patients, the interim analysis demonstrated Ribavirin administration for 3 days was associated with a greater reduction in respiratory rate and inspired oxygen concentration (P < 0.02). At follow-up, there was no significant difference between groups in the proportion of infants who were symptomatic or required re-admission to hospital for chest-related illnesses; the Ribavirin group, however, had lower airways resistance (P < 0.01) and higher specific conductance (P < 0.02). We conclude that antiviral therapy seems to speed the rate of recovery from acute respiratory deteriorations seen in preterm infants with chronic lung disease; this is associated with improved lung function, but not lower respiratory morbidity, at follow-up.

Pediatric critical care physicians' attitudes about guidelines for the use of ribavirin in critically ill children with respiratory syncytial virus pneumonia

OBJECTIVE

To determine the attitude of pediatric critical care physicians concerning the use of ribavirin in children with respiratory syncytial virus lung disease in light of the revised American Academy of Pediatrics practice guidelines.

DESIGN

A questionnaire was sent to 145 pediatric critical care doctors in the United States.

MEASUREMENTS AND MAIN RESULTS

Seventy-seven percent of questionnaires were returned. The vast majority (91%) of the respondents think that the available literature does not support the Academy's recommendations for the administration of ribavirin to critically ill children with respiratory syncytial virus pneumonia. The largest single group of respondents (42%) does not usually prescribe ribavirin for these patients, but may be persuaded to use it by colleagues or consultants in individual cases. Twenty-six percent of all respondents stated that they do not use ribavirin at any time, even in severely ill patients with documented infection. Twenty-two percent of the respondents say that they will prescribe ribavirin, not because they believe it is efficacious, but because they believe the Academy guidelines compel them to do so as a standard of care. The respondents reported adverse effects of the drug, most notably exacerbations of bronchospasm (92%), far more often than the Academy document asserts. When solicited for general comments, the respondents were frequently concerned that critical care physicians were not involved in the development of the guidelines, the guidelines were based on a paucity of reliable data, and that the guidelines could put them at risk of malpractice litigation should they choose to not use ribavirin.

CONCLUSIONS

Practice guidelines are increasingly being incorporated into patient care and quality improvement regimens, and it is imperative both that appropriate experts be included in their development, and that they be based on valid scientific data. The pediatric critical care community currently treats most of the severely ill patients with respiratory syncytial virus pneumonia. As a group, they remain unconvinced about the efficacy and safety of this drug, and many pediatricians are concerned about the ramifications of individualizing ribavirin therapy in their patients in light of the revised Academy recommendations.

Ciliary function, cell viability, and in vitro effect of ribavirin on nasal epithelial cells in acute rhinorrhea

Nasal epithelial (NE) cells were collected from the nasopharynx of 25 individuals with symptomatic colds and 27 healthy volunteers (controls), and ciliary beat frequency (CBF) was assessed by microscopy employing video motion analysis techniques. Baseline CBF was statistically significantly elevated in the group with colds compared to the control group (14.6 +/- 1.5 Hz [mean +/- SD] vs 13.8 +/- 0.9 Hz; p = 0.02). After four days of incubation in culture, there was a significant decrease in the CBF in both groups, with a change from baseline of 1.9 Hz for the cold group, compared to 1.0 Hz for the control group (p = 0.0001). The in vitro addition of ribavirin at 500 micrograms/ml to NE cells from individuals with colds preserved the viability of the cells and maintained the CBF at baseline values. Twenty-four (96 percent) of 25 ribavirin-treated specimens from the cold group survived for four days in culture, compared with 17 (68 percent) of 25 untreated cold specimens. In addition, the ribavirin-treated cells had a mean CBF of 14.2 +/- 1.3 Hz, compared with 12.7 +/- 1.9 Hz for the untreated cell samples (p = 0.0005). Ribavirin had no effect on NE cells from the control group. These results suggest that ribavirin in a concentration of 500 micrograms/ml may have some benefit in the treatment of acute rhinorrhea.

A controlled trial of aerosolized ribavirin in infants receiving mechanical ventilation for severe respiratory syncytial virus infection

BACKGROUND

Although the antiviral agent ribavirin improves the course of lower respiratory tract disease in spontaneously breathing infants with respiratory syncytial virus infection, it is not known whether ribavirin can benefit infants with severe respiratory syncytial virus disease who require mechanical ventilation.

METHODS

We conducted a randomized, double-blind, placebo-controlled evaluation of ribavirin (20 mg per milliliter) administered continuously in aerosolized form to infants receiving mechanical ventilation for respiratory failure that was caused by documented respiratory syncytial virus infection.

RESULTS

Of the 28 infants (mean [+/- SD] age, 1.4 +/- 1.7 months) enrolled, 7 had underlying diseases predisposing them to severe infection (mean age, 3.0 +/- 2.6 months), and 21 were previously normal (mean age, 0.8 +/- 0.9 month). Among the 14 infants who received ribavirin, the mean duration of mechanical ventilation was 4.9 days (as compared with 9.9 days among the 14 who received placebo; P = 0.01), and the mean length of supplemental oxygen use was 8.7 days (as compared with 13.5 days; P = 0.01). The mean length of the hospital stay was 13.3 days after treatment with ribavirin and 15.0 with placebo (P = 0.04). When only the 21 previously normal infants were considered, the mean length of the hospital stay was 9.0 days for the ribavirin recipients and 15.3 days for those who received placebo (P = 0.005).

CONCLUSIONS

In infants who require mechanical ventilation because of severe respiratory syncytial virus infection, treatment with aerosolized ribavirin decreases the duration of mechanical ventilation, oxygen treatment, and the hospital stay.

Economic and long-term benefits of ribavirin therapy on respiratory syncytial virus infection

Ribavirin is a broad-spectrum antiviral agent. Administered as an aerosol, it has been shown to be clinically effective in improving the signs and symptoms of viral bronchiolitis in infancy, particularly cases due to respiratory syncytial virus (RSV). This paper reviews the evidence for economic and/or long-term clinical benefits from using ribavirin in the acute illness. There are data to suggest that use of ribavirin may lead to a reduction in therapeutic interventions and duration of hospital stay, with associated savings in hospital costs. Ribavirin reduces the production of RSV-specific IgE, and (in vitro) inhibits the release of inflammatory mediators from mast cells, suggesting that there could be beneficial effects on the incidence of postbronchiolitis wheezing. Confirmatory studies are in progress.

Nebulized albuterol in acute bronchiolitis

In a double-blind, placebo-controlled trial, 40 infants between 6 weeks and 24 months of age who had a first episode of wheezing and other signs and symptoms of bronchiolitis were randomly assigned to receive either nebulized albuterol (0.15 mg/kg/dose) or placebo (saline solution) for two administrations 1 hour apart. The albuterol therapy resulted in a significantly greater improvement in the accessory muscle score (decreases 0.70 vs decreases 0.30; p = 0.03), oxygen saturation (increases 0.71% vs decreases 0.47%; p = 0.01) after one dose, and in the accessory muscle score (decreases 0.86 vs decreases 0.37; p = 0.02), respiratory rate (decreases 19.6% vs decreases 8.0%; p = 0.016), and oxygen saturation (increases 0.76% vs decreases 0.79%; p = 0.015) after two doses of the drug. The response to therapy was similar in infants younger and those older than 6 months of age. The heart rate rose slightly more in the albuterol group (increases 7.76 from baseline) versus the placebo group (decreases 6.79). There were no other side effects of the treatment. Of the 34 children from whom nasal specimens were obtained by swab for viral identification, 24 had positive test results (21 for respiratory syncytial virus, 1 for parainfluenza, 1 for paramyxovirus, and 1 for influenza A). We conclude that nebulized albuterol constitutes a safe and effective treatment of infants with bronchiolitis.

What is the clinical role of aerosolized ribavirin?

Aerosolized ribavirin is the first approved agent for the treatment of respiratory syncytial virus (RSV) infection. However, the clinical use of ribavirin is controversial. Although ribavirin-treated patients appear to be subjectively improved, the benefit in terms of decreased morbidity and mortality is not well established. Furthermore, the drug has been found to be teratogenic, carcinogenic, and mutagenic, depending upon the scientific model. Because of its unique mode of administration, environmental exposure of healthcare personnel and other patients may occur. Although administration in mechanically ventilated patients decreases the amount of ribavirin liberated into the atmosphere, the drug crystallizes in the endotracheal tube, occasionally resulting in reduced ventilation. The lack of data documenting efficacy and the above environmental concerns result in difficult decisions for hospitals. Further studies are necessary to clarify the value and safety of ribavirin in the treatment of RSV infection.