***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE To study the occurrence of bronchial obstructive symptoms and immunoglobulin ( Ig ) E antibodies after respiratory syncytial virus ( RSV ) bronchiolitis in infancy . Previous studies of this subject have mostly been retrospective or without controls , or the controls have not been followed prospect ively . DESIGN This was a prospect i ve cohort study with matched controls . PARTICIPANTS Forty-seven infants had experienced RSV bronchiolitis severe enough to cause hospitalization at a mean age of 3 1/2 months . For each child with RSV infection , two controls were acquired from the local Child Health Center and matched for date of birth , sex , and residence . Only one control was obtained for one RSV child , and the control group thus contained 93 children . METHODS All the children underwent two follow-up examinations , the first one at a mean age of 1 year and the second at a mean age of 3 years . At the first follow-up , a  skin-prick test against egg white  was performed , and serum  IgG antibodies  against RSV were measured . At the second follow-up , serum IgE antibodies  were measured using screening tests for common food and inhalant antibodies , and  skin-prick tests against egg white , cat , birch , and mite allergen were performed . Hereditary and environmental factors ( passive smoking , indoor furred animals ) and duration of breast-feeding were recorded . RESULTS At the first follow-up , 89 % in the RSV group and 27 % in the control group had IgG antibodies against RSV ( P < .001 ) . At the second follow-up , asthma , defined as three episodes of bronchial obstruction verified by a physician , was found in 11 of 47 children ( 23 % ) in the RSV group and in 1 of 93 children ( 1 % ) in the control group ( P < .001 ) . A positive test for IgE antibodies was noted in 14 of 44 ( 32 % ) RSV children and in 8 of 92 ( 9 % ) children in the control group ( P = .002 ) . An analysis of risk factors for the development of asthma and IgE antibodies on the whole group of 140 children showed that RSV bronchiolitis was the most important risk factor , and a family history of atopy or asthma further increased the risk . CONCLUSIONS Respiratory syncytial virus bronchiolitis during the first year of life apparently is an important risk factor for the development of asthma and sensitization to common allergens during the subsequent 2 years , particularly in children with hereditary for atopy/asthma AIM To study the outcome in early adulthood for children with early asthma symptoms  and to analyse the factors associated with current asthma . METHODS In a prospect i ve study , we have re-investigated 89/101 children who were hospitalized before the age of two years due to wheezing . The children were investigated using a question naire and allergy and bronchial hyper-responsiveness tests at the age of 17 - 20 years and compared with age-matched controls . RESULTS In the cohort , 43 % had had asthma symptoms in the preceding 12 months compared with 15 % in the control group . The strongest risk factors for asthma were current allergy , bronchial hyper-responsiveness and female gender . Female gender and passive smoking in infancy were independent infantile risk factors . In addition to female gender , two pathways led to current asthma : an allergic pathway from family atopy via the development of allergy and another pathway from early passive smoking via hyper-responsiveness and active smoking . CONCLUSION In children with early wheezing disorder , current allergy , bronchial hyper-responsiveness and female gender were the strongest risk factors for asthma in early adulthood , while female gender and passive smoking in infancy were independent infantile risk factors . The effects of early passive smoking persist longer than previously reported Epidemiological data suggest that respiratory syncytial virus ( RSV ) infection in early life is a risk factor for later asthma .  There are no prospect i ve studies on RSV infection starting from infancy progressing through childhood into adulthood . We followed up a cohort of children , hospitalized for RSV bronchiolitis or RSV pneumonia before age 24 months , until age 18 - 20 years . The aim of the study was to evaluate early RSV infection as a risk factor for  asthma , bronchial reactivity , and lung function abnormalities in young adults . The participants filled in a question naire on asthma and asthma-like symptoms . The clinical study included flow-volume spirometry ( FVS ) , methacholine inhalation challenge ( MIC ) , home PEF ( peak expiratory flow ) monitoring , and skin prick tests ( SPT ) to common allergens .  Asthma was present in 17 - 22 % of 36 index subjects , depending on asthma definition , compared to 11 % of 45 controls . Furthermore , FEV% and MEF25 were lower , and MEF50 tended to be lower , in index than in control subjects . One or more abnormal lung function results were found in 16 ( 44 % ) index subjects , but only in 5 ( 11 % ) controls ( P < 0.01 ) . Bronchial reactivity ( PD20 < 4,900 microg methacholine ) was demonstrated in 16 ( 46 % ) index subjects and 14 ( 32 % ) controls ( NS ) . At least one positive SPT result was present in 21 ( 60 % ) index subjects ; 6 ( 29 % ) had asthma ( NS vs. nonatopic index subjects ) ; 13 ( 62 % ) had abnormal lung function ( P < 0.05 ) ; and 14 ( 67 % ) had bronchial reactivity ( P < 0.01 ) . In the logistic regression adjusted for atopy , as defined by SPT positivity , RSV infection in infancy was an independent risk factor for lung function abnormality ( one or more abnormal results in FVS ; OR , 5.27 ; 95 % CI , 1.60 - 17.36 ) , and also for decreased FEV% and MEF50 when these were analyzed separately . However , RSV infection in infancy was not a significant risk factor for asthma or bronchial reactivity . In young adults , lung function abnormalities may be associated with RSV infection which required hospitalization in infancy This paper review s the results from a cohort study in which 47 children hospitalised with respiratory syncytial virus ( RSV ) bronchiolitis and their 93 controls , matched for age , sex and place of living , were prospect ively followed-up at the mean ages of 1 , 3 and 7.5 . Asthma was significantly more common in the RSV bronchiolitis group at all times . Asthma during the year prior to follow-up at age 7.5 was seen in 23 % of the RSV children and in 2 % of the controls ( P < 0.001 ) . Allergic sensitisation was found in 41 % of the RSV children and in 22 % of the controls ( P = 0.039 ) . When comparing these results with findings from other studies it is obvious that the rate of asthma and other bronchial obstructive symptoms are increased after RSV bronchiolitis but the various results concerning allergic sensitisation are not conclusive . Prospect i ve studies are needed with some kind of r and omised intervention against RSV before the mechanisms behind the post-bronchiolitic symptoms and the possibly increased risk for IgE mediated allergy can be settled Acute viral respiratory illness during infancy has been implicated as a precursor for subsequent  lower respiratory morbidity in childhood . A prospect i ve , longitudinal study of respiratory function , airway responsiveness , and lower respiratory illness during early childhood was performed in a cohort of 253 healthy infants to characterise those who experienced bronchiolitis . Seventeen infants ( 7 % of the cohort ) , were given a diagnosis of bronchiolitis during the first two years of life with two ( 1 % ) requiring hospital admission . Seventy one per cent of those infants with bronchiolitis had a family history of atopy , 53 % of asthma , and 29 % had a mother who smoked cigarettes . These family history characteristics in this group with bronchiolitis were not different from the rest of the cohort . There were also no differences in the number of older siblings , the number breast fed , the duration of breast feeding , or socioeconomic status of the families between those that did and did not get bronchiolitis . Respiratory function was assessed at 1 , 6 , and 12 months of age . Maximum flow at functional residual capacity ( VmaxFRC ) was measured using the rapid thoracic compression technique . Resistance ( Rrs ) and size corrected compliance ( Crs/kg ) were obtained from a single brief occlusion at end inspiration . Airway responsiveness was assessed by histamine inhalation challenge and the provocation concentration of histamine result ing in a 40 % fall on VmaxFRC from baseline ( PC40 ) was determined . Respiratory measurements were ranked into terciles to assess the distribution of infants who developed bronchiolitis through the cohort . Cough and wheeze were noted to be frequent before the episode of bronchiolitis . This study has demonstrated that infants who develop bronchiolitis have evidence of pre-existing reduced respiratory function and lower respiratory symptoms . It is proposed that bronchiolitis , although potentially contributory , is not usually causative of subsequent lower respiratory morbidity OBJECTIVE To determine the outcome until adulthood after wheezing in infancy , compared with pneumonia in infancy and with controls . DESIGN An 18- to-20-year prospect i ve cohort study . SETTING Pediatric department at a university hospital , providing primary hospital care for a defined population . Patients Fifty-four children hospitalized for bronchiolitis and 34 for pneumonia at younger than 2 years , and 45 controls with no early-life wheezing or hospitalization , were studied at median age 19 years . MAIN OUTCOME MEASURES A question naire on  asthma symptoms and medication , physical examination , flow volume spirometry ( FVS ) , methacholine inhalation challenge ( MIC ) , home peak expiratory flow ( PEF ) monitoring , and skin prick testing ( SPT ) to common inhalant allergens .  The 2 asthma definitions were physician-diagnosed asthma and previously diagnosed asthma with recent asthmatic symptoms ( physician-diagnosed asthma included ) . RESULTS By the 2 definitions , asthma was present in 30 % ( odds ratio [ OR ] , 3.37 ; 95 % confidence interval [ CI ] , 1.12 - 10.10 ) and in 41 % ( OR 1.38 ; 95 % CI , 0.37 - 5.21 ) in the bronchiolitis group , in 15 % ( OR , 5.50 ; 95 % CI , 1.87 - 16.14 ) and in 24 % ( OR , 2.07 ; 95 % CI , 0.59 - 7.22 ) in the pneumonia group , and in 11 % in the control group . After bronchiolitis , the FVS values were forced vital capacity ( FVC ) , 108 % ( SD , 13 % ) of predicted ; forced expiratory volume in 1 second , 98 % ( SD , 12 % ) ; forced expiratory volume in 1 second divided by FVC , 91 % ( SD , 7.6 % ) ; midexpiratory flow at 50 % of the FVC , 74 % ( SD , 19 % ) ; and midexpiratory flow at 25 % of the FVC , 74 % ( SD , 22 % ) . Bronchial reactivity by MIC was present in 25 ( 48 % ) of 52 subjects in the bronchiolitis group , in 13 ( 42 % ) of 31 in the pneumonia group , and in 14 ( 32 % ) of 44 in the control group . The prevalence of atopy ( positive SPTs ) was 48 % to 63 % in the 3 groups . In a logistic regression adjusted for atopy and smoking , infantile bronchiolitis was an independent risk factor for asthma by both definitions . CONCLUSION The increased risk for asthma persists until adulthood after bronchiolitis in infancy Severe respiratory syncytial virus ( RSV ) infection has been hypothesised to be a risk factor for the development of allergy and asthma , but epidemiological studies in older children have been inconclusive . The current study hypothesises that the effect of RSV bronchiolitis might be most prominent during the first year after bronchiolitis . Forty-two infants had experienced RSV bronchiolitis severe enough to cause hospitalisation . For each child with RSV infection , two controls were acquired from a birth cohort and matched for date of birth and sex . All the children were followed prospect ively and underwent a follow-up examination at a mean age of 1 yr , which included physical examination , and serum immunoglobulin ( Ig ) E tests for common food and inhaled allergens . Risk factors for the development of recurrent wheezing and IgE antibodies were analysed for the whole group of 126 children . A positive test for IgE antibodies was noted in 14 of 42 ( 33 % ) RSV children and in 2 of 84 ( 2.3 % ) children in the control group . RSV bronchiolitis was the most important risk factor for allergic sensitisation . Likewise , 13 children ( 15.5 % ) of the RSV group and three ( 3.6 % ) children of the control group suffered from recurrent wheezing , and RSV bronchiolitis posed a considerable risk for recurrent wheezing . Severe 
    Output:
    
The studies evaluated showed that RSV lower respiratory tract infection is associated with an increased risk for subsequent development of asthma/recurrent wheezing , and that this association becomes progressively smaller with increasing age .
On the basis of this systematic review of the literature , it can be concluded that a significant association exists between RSV infection in childhood and the long-term development of subsequent episodes of recurrent wheezing or asthma .