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PubMed1998

Severity of respiratory syncytial virus disease related to type and genotype of virus and to cytokine values in nasopharyngeal secretions.

BACKGROUND: Investigations concerning the severity of respiratory syncytial virus (RSV) disease as related to (1) RSV type and genotype determined respectively by PCR and restriction enzyme analysis and (2) interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) values in samples of nasopharyngeal secretion (NPS) have not been previously reported. METHODS: We prospectively studied 105 RSV infections in the lower respiratory tract of infants and young children admitted to a pediatric department in Copenhagen during three winter seasons, 1993, 1994 and 1995. RSV strains were typed and genotyped, respectively, by PCR and nucleic acid restriction analysis and correlated to the severity of the disease. The ratio IL-6:TNF-alpha, determined from IL-6- and TNF-alpha values in samples of NPS, was related to the severity of the disease. Concentrations of IL-6 and of TNF-alpha were determined in serum samples taken during 5 weeks after the onset of illness. RESULTS: Type B infections produced more severe disease than did type A infections, as assessed on the length of the hospital stay, use of respiratory support and the presence of an infiltrate on a chest radiograph. This difference was age-related. It was observed in infants 0 to 5 months old, but not in older age groups. Type B genotype B1122 produced more severe disease than type A genotype A2311 in infants 0 to 11 months old. Increased serum concentrations of IL-6 and TNF-alpha were detected in samples taken 1 to 2 days after the onset of illness. Whereas TNF-alpha serum concentrations remained high, IL-6 serum concentrations decreased during the following 3 to 4 weeks. The IL-6:TNF-alpha ratio in samples of NPS was related to the severity of the disease. A high ratio was related to a low severity. CONCLUSIONS: The severity of disease in patients admitted with acute RSV infections can be correlated to the RSV type as determined by PCR, to the RSV genotype as determined by nucleic acid restriction analysis and to the ratio IL-6:TNF-alpha in NPS.

Child, Preschool↗
PubMed2000

Enzyme-linked immunosorbent assay to assess respiratory syncytial virus concentration and correlate results with inflammatory mediators in tracheal secretions.

OBJECTIVE: We developed an enzyme-linked immunosorbent assay (ELISA) for the quantitation of respiratory syncytial virus (RSV) in respiratory secretions in intubated patients infected with RSV. METHODS: We compared the quantitative ELISA and a standardized plaque assay in intubated children <2 years of age who were mechanically ventilated for severe RSV disease and enrolled in a randomized double blind placebo-controlled treatment trial of a monoclonal antibody to the F protein of RSV (palivizumab; Synagis). We also examined the relationship between the concentrations of virus as measured by ELISA and of three inflammatory indices in respiratory secretions (white blood cell count, myeloperoxidase and eosinophilic cationic protein). RESULTS: Quantitative ELISA and plaque assay were highly correlated for both tracheal aspirates (r = 0.67, P = 0.001) and nasal wash specimens (r = 0.75, P = 0.001). Treatment with palivizumab significantly neutralized RSV in tracheal aspirates as measured by plaque assay. In contrast quantitation of RSV by ELISA was not affected by palivizumab treatment. This finding is consistent with results that were obtained in preliminary studies of RSV-containing media treated with monoclonal antibody, where we found that the ELISA measured virus whether antibody-bound or not. The inflammatory indices were not correlated with RSV concentration measured by ELISA or plaque assay. CONCLUSIONS: We conclude that this quantitative ELISA is a potentially useful tool for measurement of RSV concentration in respiratory secretions that may help elucidate the pathophysiology of acute RSV infection. Specific antiviral strategies for the treatment of RSV disease could be evaluated by this method.

Child, Preschool↗
PubMed2000

Rehospitalization because of respiratory syncytial virus infection in premature infants younger than 33 weeks of gestation: a prospective study. IRIS Study Group.

OBJECTIVE: To collect data on hospitalization for respiratory syncytial virus (RSV) infections and presumptive risk factors for rehospitalization among premature infants in Spain. DESIGN: Observational, prospective, longitudinal, multicenter study. SETTING: Fourteen Spanish neonatal units with an annual birth cohort of 57,000 infants. PATIENTS: All children (n = 680) born < or =32 weeks of gestational age between April 1, 1998, and March 31, 1999, and discharged from the hospital before March 31, 1999, were included in the study. A total of 96 were excluded because of administration of prophylactic treatment (n = 55) or were lost to follow-up (n = 41). Five children died during the study period, but death was related to RSV in only 1 case. METHODS AND MAIN OUTCOME MEASURES: Neonatal and demographic data were recorded at the initial visit. Infants were prospectively followed at monthly intervals up to March 31, 1999. In patients rehospitalized for respiratory disorders, further data about RSV status and morbidity were collected. A comparison was made between children rehospitalized for RSV infection and those who were not. The influence of factors on the probability of rehospitalization for RSV infection was assessed by logistic regression analysis. RESULTS: Of the 584 evaluable patients 118 (20.2%) were rehospitalized for respiratory disease during the study period. The causative pathogen was identified in 89 (75.4%) hospital admissions. Of these 59 (66.3%) were a result of RSV infection in 53 children; 6 were reinfections. In a logistic regression model significant independent prognostic variables included: lower risk of RSV hospitalization with increase gestational age [odds ratio (OR), 0.85; 95% confidence interval (CI), 0.72 to 0.99; P < 0.047]; higher risk with chronic lung disease (OR = 3.1; 95% CI 1.22 to 7.91; P < 0.016); and living with school age siblings (OR = 1.86; 95% CI 1.01 to 3.4; P < 0.048). CONCLUSION: This large descriptive study has enabled us to define the influence of specific risk factors that increase the risk of rehospitalization for RSV infection in preterm infants. Such studies help to define the appropriate role of available prophylactic interventions and establish treatment guidelines.

Child, Preschool↗
PubMed2001

Airflow limitation during respiratory syncytial virus lower respiratory tract infection predicts recurrent wheezing.

BACKGROUND: Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) is frequently followed by recurrent wheezing. Thus far no clinical risk factors have been identified to predict which infants will have wheezing episodes subsequent to RSV LRTI. OBJECTIVE: To determine clinical predictors for airway morbidity after RSV LRTI. METHODS: In a 1-year follow-up study we investigated the predictive value of auscultatory findings characteristic of airflow limitation (wheezing) during RSV LRTI for subsequent airway morbidity. Clinical characteristics, including the presence or absence of signs of airflow limitation, of hospitalized infants with RSV LRTI were prospectively recorded during 2 winter epidemics. During a 1-year follow-up period parents of 130 infants recorded daily airway symptoms. OUTCOME MEASURE: Recurrent wheezing defined as > or = 2 episodes of wheezing. RESULTS: Signs of airflow limitation during RSV LRTI were absent in 47 (36%) infants and present in 83 (64%) infants. Recurrent wheezing was recorded in 10 (21%) infants without signs of airflow limitation and in 51 (61%) with signs of airflow limitation during initial RSV LRTI (relative risk, 0.29, P < 0.001). In a multiple logistic regression model, airflow limitation during initial RSV LRTI proved independent from other clinical parameters, including age, parental history of asthma and smoke exposure. CONCLUSIONS: A sign of airflow limitation during RSV LRTI is the first useful clinical predictor for subsequent recurrent wheezing.

Auscultation↗
PubMed2001

Molecular detection of respiratory syncytial virus in postmortem lung tissue samples from Mexican children deceased with pneumonia.

BACKGROUND: Respiratory syncytial virus (RSV) is the major viral cause of severe respiratory infections in children younger than 2 years of age. Nevertheless there are not enough epidemiologic data about the role of RSV as a cause of infantile mortality from pneumonia, mainly in young children from developing countries Aim. To determine the frequency of RSV infection in lung tissue samples from Mexican children deceased with pneumonia, by reverse transcription (RT) and PCR. METHODS: Postmortem lung tissue samples from 98 children younger than 2 years of age who died of pneumonia during the period of 1989 to 1997 were studied. Paraffin was removed with xylene from 10-microm lung sections, the total RNA was extracted and complementary DNA was obtained by RT reaction. A nested PCR with the use of oligonucleotides specific for the F glycoprotein gene was developed. Samples negatives for RSV were tested for the absence of polymerase inhibitors and for complementary DNA integrity. RESULTS: Twenty-nine of the 98 (30%) children deceased with pneumonia were positive for RSV by RT-PCR; 8 were detected from 13 (62%) children with histopathologic diagnosis of viral pneumonia and 21 from 85 (25%) children with histopathologic diagnosis of bacterial pneumonia (P = 0.018). There was no significant difference in RSV infection according to age groups or seasonal pattern. CONCLUSIONS: RSV infection is frequent in Mexican children younger than 2 years of age who died of pneumonia. Although RSV was more common in viral pneumonia, mixed infections with RSV and bacterial pneumonia were also common.

Autopsy↗
PubMed2001

Hospitalization rates for respiratory syncytial virus infection in premature infants born during two consecutive seasons.

OBJECTIVE: To collect data on hospitalization rates for respiratory syncytial virus (RSV) illness during the season of 1999 to 2000 in nonprophylaxed premature infants < or = 32 weeks gestational age (GA) in Spain and compare this with previously published data collected in the season of 1998 to 1999. METHODS: Children born at < or = 32 weeks GA between April 1, 1999, and April 31, 2000, and discharged from the hospital before April 31, 2000, were included. Neonatal and demographic data were obtained at the initial visit. Study subjects were followed at monthly intervals throughout the respiratory season. RSV status and morbidity data were collected on patients rehospitalized for respiratory illness. RESULTS: The 999 evaluable patients in the 2000 season were comparable to the 1999 sample, except for higher rates of family allergy history and number of multiple deliveries and a lower rate of neonatal morbidity. The hospitalization rate for RSV illness was 13.4% in the 1999 season and 13.1% in the 2000 season; 10 (8%) were RSV reinfections in the 2000 season. Significant independent prognostic variables for high risk of RSV hospital admission included: lower gestational age; chronologic age < 3 months at onset of the RSV season; living with school age siblings; and exposure to tobacco smoke. CONCLUSIONS: Hospitalization rates for RSV disease in nonprophylaxed preterm infants < or = 32 weeks GA were high in Spain and comparable during two consecutive RSV seasons (13%). Readmission for a second RSV infection was also common.

Analysis of Variance↗
PubMed2002

Epidemiology and clinical presentation of respiratory syncytial virus infection in a rural area of southern Mozambique.

BACKGROUND: Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection (LRTI) in infants throughout most of the world, but little is known about RSV infection in Africa where LRTI are among the leading causes of infant and childhood death. METHODS: The study took place in a rural district hospital in southern Mozambique between October, 1998, and May, 2000. From all children (n = 5635) <1 year of age presenting to an outpatient department with cough or nasal secretion and all children (n = 1307) <5 years of age admitted to hospital with a LRTI, a nasopharyngeal aspirate was collected and tested for RSV by enzyme-linked immunosorbent assay (Abbott). RESULTS: RSV infection was found in 8.6% of study infants in the outpatient department and 10.6% of admitted children with LRTI. Cases presented in predictable yearly outbreaks during the warm and rainy season. Lower respiratory tract involvement was frequent (59.7%). Cough, chest indrawing and increased respiratory rate were all independently related to RSV infection. Wheezing was infrequent. Bacterial coinfection (4.6%) and the case-fatality rate (3.4%) were low. CONCLUSIONS: There is a substantial burden of disease attributable to RSV infection in this rural African setting, with the highest incidence and severity occurring in young infants.

Bacterial Infections↗
PubMed2002

Palivizumab prophylaxis for respiratory syncytial virus in Canada: utilization and outcomes.

OBJECTIVE: To provide information on the use and outcomes of palivizumab prophylaxis in children at high risk of serious respiratory syncytial virus (RSV) infection. DESIGN: Observational, prospective, longitudinal, multicenter study. SETTING: Eighteen hospitals and pediatric clinics located in six provinces across Canada. PATIENTS: Infants enrolled in the palivizumab Special Access Programme of Canada's Therapeutic Products Programme throughout the 1999 to 2000 RSV season. Most were premature infants born at < or = 32 weeks of gestation and/or had bronchopulmonary dysplasia. METHODS AND MAIN OUTCOME MEASURES: Neonatal and demographic data were recorded for each subject. The parent/caregiver was contacted on a monthly basis until the end of the RSV season to obtain information on palivizumab utilization and compliance as well as incidence and severity of respiratory infections. RESULTS: There were 444 evaluable subjects who each received 1 to 7 injections of palivizumab for a total of 1702 doses from September 1999 to April 2000. Most subjects received 5 injections with high compliance. Prophylaxis was discontinued in 2% of children. There were 116 clinical events or hospitalizations involving respiratory tract infections reported in 91 children. Eighty-six of these were managed in an outpatient setting, and 30 required hospitalization. The estimated incidence of hospitalization for RSV-positive lower respiratory tract infections (LRTIs) was 2.4%. Hospitalization for RSV LRTI occurred more often in children with bronchopulmonary dysplasia (6.0%) than in those with prematurity only (1.6%). CONCLUSIONS: This study demonstrates that prophylaxis with palivizumab during the RSV season was associated with a low rate of hospitalization for RSV-positive LRTIs. Palivizumab was well-tolerated, and compliance was high. The findings confirm the results of the major randomized clinical trial of palivizumab and demonstrate the safety and effectiveness of RSV prophylaxis.

Antibodies, Monoclonal↗
PubMed2002

Respiratory syncytial virus-coded pediatric hospitalizations, 1997 to 1999.

BACKGROUND: The recent number and rate of infant hospitalizations with a respiratory syncytial virus (RSV)-coded diagnosis have not been published. METHODS: Retrospective data analysis. National Hospital Discharge Survey data for 1997 to 1999 were analyzed for discharges of infants < 1 year old with an RSV-coded diagnosis (ICD-9-CM 466.11, 480.1, 079.6). Hospitalization rates were estimated with annual midyear Census data. RESULTS: RSV bronchiolitis was the leading primary diagnosis annually for all infants hospitalized for any reason. Between 1997 and 1999, 297 684 RSV-coded discharges of infants with an RSV-coded diagnosis occurred. The associated hospitalization rate was 25.2 per 1000 infants. RSV-coded discharges peaked in February. CONCLUSION: RSV bronchiolitis was the leading cause of hospital admissions of infants younger than age 1 year for any reason between 1997 and 1999.

Acute Disease↗
PubMed2002

Current concepts on active immunization against respiratory syncytial virus for infants and young children.

Respiratory syncytial virus (RSV) is the most important causative agent of viral respiratory tract infections in infants and young children. Passive immunization against RSV became available recently, but this does not apply to an effective vaccine as a result of dramatic adverse results of immunization with a RSV candidate vaccine in the 1960s and the lack of full knowledge of the immune response induced by RSV. Nonetheless intensive research during the past two decades has resulted in several interesting candidate vaccines, of which some have gone through testing in humans. These include the subunit vaccines PFP-1, PFP-2, BBG2Na and cold-passaged/temperature-sensitive mutants. The development of candidate vaccines against RSV is discussed. Because of questions, uncertainties and difficulties with the development of effective vaccines against RSV, it will probably be at least another 5 to 10 years before routine immunization against RSV becomes available.

Animals↗
PubMed1998

Continuous non-seasonal epidemic of respiratory syncytial virus infection in the southeast United States.

BACKGROUND: This study was done to define the seasonality of respiratory syncytial virus (RSV) epidemics in the southeastern United States. METHODS: We tested 5,092 fresh nasal aspirates or washings, using the Kallestad Pathfinder enzyme immunoassay (EIA) or the Directigen RSV membrane EIA according to manufacturers' directions. RESULTS: A total of 1,419 (27.9%) respiratory specimens, collected from pediatric patients between May 1993 and December 1996 at two large southeastern medical centers, were positive for RSV antigen by enzyme immunoassay. A persistent RSV epidemic was documented between July 1993 and December 1996. We defined an epidemic as 2 consecutive months in each of which > or = 10% of the specimens were positive and > or = 2 positive specimens detected. The highest percentages of positive specimens were detected in December of 1993, 1994, and 1996, to date, and November 1995. CONCLUSION: On the basis of our findings, we recommend health care workers consider RSV in the differential diagnosis of acute respiratory illness throughout the year in pediatric patients from the southeast United States.

Antigens, Viral↗
PubMed2002

Respiratory syncytial virus infection: clinical features, management, and prophylaxis.

Respiratory syncytial virus (RSV) infects almost all children by two years of age, resulting in a large number of hospital admissions in infants. Reactive airway disease is more common after RSV infection, even in previously healthy children. Management of the acute infection is supportive, but preliminary evidence suggests surfactant administration to ventilated infants may be of benefit. Whether ribavirin or corticosteroids reduce respiratory morbidity after RSV infection remains controversial. Immunoprophylaxis reduces RSV admissions, Palivizumab, a humanized monoclonal antibody, is a more cost-effective prophylaxis than RSV immune globulin. Nevertheless, the cost of prophylaxis, unless only given to very high-risk infants, exceeds savings made in reducing admissions.

Antibodies, Monoclonal↗
PubMed2003

Incidence and clinical features of hospitalization because of respiratory syncytial virus lower respiratory illness among children less than two years of age in a rural Asian setting.

BACKGROUND: Lower respiratory illness is the leading cause of child death in the developing world. Despite this few reports on respiratory syncytial virus (RSV) lower respiratory illness disease burden exist from rural areas of the developing world, and none exist for Indonesia. METHODS: We evaluated children living in any of 83 villages on Lombok Island, Indonesia who were <2 years of age when hospitalized for severe lower respiratory illness during 2000 and 2001. All hospitals on Lombok were included in the evaluation. We obtained the number of births and deaths that occurred within the study villages and time frame, allowing for incidence determination. RESULTS: Of 2677 children hospitalized for severe lower respiratory illness whose RSV status was determined, 23% had a positive test; this percentage varied from 50% at the end of the rainy season to 0% shortly before the start of the rainy season. Among children <2 years of age, the confirmed and estimated incidences of severe RSV lower respiratory illness hospitalization were 10 and 14 per 1000 child-years, respectively; values for children <1 year of age were 17 and 25 per 1000 child-years. The confirmed case-fatality percentage among RSV-positive cases was 1.9%; however, 84% of children who died were dead before RSV status could be determined, suggesting the actual case fatality percentage was higher. CONCLUSIONS: Lombok has a large burden of severe childhood RSV lower respiratory illness, and death occurs frequently. Novel RSV vaccines thus could have a substantial positive impact on lower respiratory illness morbidity and mortality.

Age Distribution↗
PubMed2003

Respiratory syncytial virus and other respiratory viruses.

Respiratory syncytial virus (RSV), a nonsegmented, single stranded RNA virus, infects one-half of all infants within the first year of life. RSV possesses pathogenetic qualities that may be attributed to the interplay of viral and host-specific factors including virus strains of different virulence, size of the inoculum, family history of asthma or airway hyperreactivity and immunologic anomalies of the host. Inflammatory cell recruitment and activation occur in response to RSV infection of epithelial cells. Epithelial cells initiate the inflammatory response to RSV by elaborating a wide variety of cytokines and chemokines that trigger further inflammatory responses. Helper T lymphocytes mediate the relative balance of cytokine production and also secrete a variety of antiviral and proinflammatory interleukins. Elevated levels of macrophage-inflammatory protein-1-alpha, an attractant of eosinophils, and monocyte chemotactic protein-1 parallel severe forms of bronchiolitis. Macrophage-inflammatory protein-1-alpha and monocyte chemotactic protein-1 levels also are inversely related to oxygen saturation, suggesting that severity of RSV disease may be linked to chemokine release. Children known to be eosinophilic during an episode of bronchiolitis appear more prone to wheeze at an older age. Influenza, parainfluenza and metapneumoviruses share major epidemiologic risk factors for lower respiratory tract infection similar to those of RSV. Like RSV some of these viruses may also promote an exaggerated lymphocyte-proliferative response, and subjects infected with parainfluenza viruses produce elevated levels of virus-specific IgE. Preliminary evidence suggests that severe RSV and influenza viral infections are mediated via chemokine up-regulation.

Antibody Formation↗
PubMed2003

Respiratory syncytial virus epidemics: the ups and downs of a seasonal virus.

Respiratory syncytial virus (RSV) is the most common pathogen causing lower respiratory tract infections in infants worldwide. Lower respiratory tract infections caused by RSV occur epidemically, and the appearance of epidemics seems to vary with latitude, altitude and climate. This study uses a review of the literature on RSV seasonality to investigate whether a global pattern in RSV epidemics can be found. A comparison of morbidity and mortality caused by RSV in developed vs. developing countries is also presented. The seasons in which RSV epidemics occur typically depend on geographic location and altitude. During these seasons the epidemics tend to appear in clusters. Although the appearance pattern of these epidemics varies from one continent to another, they usually begin in coastal areas. RSV is the cause of one-fifth of lower respiratory infections worldwide. Generally RSV mortality is low, with a median value of zero. However, RSV mortality in developing countries is significantly higher than RSV mortality in developed countries.

Child↗
PubMed2003

Links between respiratory syncytial virus bronchiolitis and childhood asthma: clinical and research approaches.

This review examines the relationship between severe pulmonary disease caused by respiratory syncytial virus (RSV) infection in infancy and later development of asthma or reactive airway disease (RAD). RSV infection accounts for 70% or greater of all cases of infantile bronchiolitis and has been linked to subsequent asthma or RAD, either directly or through a shared common predisposition. Several studies suggest that RSV bronchiolitis is an important factor in the development of asthma and possibly atopy, although the association is lost by the age of 13 years. The mechanism is as yet unclear, but murine models of RSV disease have identified many plausible causal explanations. Further study is necessary to determine the relative roles of RSV infection and genetic predisposition in explaining the association between RSV infection and asthma/RAD.

Age Factors↗
PubMed2003

Contribution of neuroimmune mechanisms to airway inflammation and remodeling during and after respiratory syncytial virus infection.

A number of studies have implicated severe infections early in life as a risk factor for the subsequent development of asthma. In particular it has been suggested that respiratory syncytial virus (RSV) infection may enhance the development of "allergic" inflammatory responses when the host is exposed to allergens after an episode of bronchiolitis. It has also been suggested that neuronal mechanisms are important in RSV infection and subsequent airway hyperreactivity. Recently we advanced the hypothesis that immune and neuronal mechanisms may be linked and that combined neuroimmune responses may be in play. In the airways a dense network of sensory nerve fibers is strategically placed just below the epithelial surface so that any change in the bronchial environment may stimulate the release of the proinflammatory neuropeptide substance P. During RSV infection, stimulation of these nerves causes a marked increase in airway vascular permeability over that in pathogen-free rats and results in an increase in overall inflammatory status. Our work has revealed that these changes are mediated by the high affinity receptor for substance P [neurokinin (NK) 1 receptor], the expression of which is greatly increased by RSV. This up-regulation presumably occurs at the gene expression level, as NK1 receptor mRNA levels increase substantially during RSV infection. We have also shown that T lymphocyte subpopulations within the bronchial-associated lymphoid tissue in the lungs of RSV-infected rats express high levels of the NK1 receptor. As a consequence stimulation of the sensory nerves by any airborne irritant has the potential of causing a new inflammatory cycle mediated by NK1 receptor-expressing T lymphocytes attracted into the airways and activated by substance P. This mechanism may establish important neuroimmune interactions, which undergo long term dysregulation after RSV infection and predispose to airway inflammation and hyperreactivity. Finally our most recent studies show that RSV infection promotes a large increase in the expression of nerve growth factor (NGF) and neurotrophin receptors. RSV-induced release of NGF leads to short and long term changes in the distribution and reactivity of sensory nerves across the respiratory tract, participating to exaggerated inflammatory reactions during and after the infection. NGF and its receptors may also amplify other immunoinflammatory and neuronal pathways contributing to airway inflammation and hyperreactivity. On the basis of these observations, we postulate that changes of neurotrophin expression in the respiratory tract may represent an important link between early life viral infections and childhood asthma.

Animals↗
PubMed2003

Respiratory syncytial virus bronchiolitis and the pathogenesis of childhood asthma.

There is now convincing evidence that children who develop lower respiratory symptoms during infection with respiratory syncytial virus (RSV) in early life are at increased risk of developing asthma-like symptoms during the school years. What determines this association is not well-understood, but increased likelihood of allergic sensitization plays a minor role, if any, as a determinant of post-RSV wheeze. Current evidence suggests that both genetic and environmental factors determine the type of immune response to the acute RSV infection and that this response, in turn, may affect the development of the control mechanisms involved in the regulation of airway tone. Many different cytokines appear to play a role in this acute immune response, including interferon-gamma; interleukins 8, 10 and 12; and cytokines produced by T helper (Th) 1 and Th2 cells. Because asthma is a heterogeneous condition, future studies will need to determine the potentially different role of RSV infection as a risk factor for these different asthma phenotypes. It is likely, however, that strategies for the prevention of RSV infection may play a role in the prevention of the subsequent development of persistent wheezing and asthma-like symptoms in childhood.

Asthma↗