MINI-SYMPOSIUM: RESPIRATORY PROBLEMS IN THE DEVELOPING WORLDAcute viral bronchiolitis and its sequelae in developing countries
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INTRODUCTION
Acute viral bronchiolitis (AVB) is the most frequent cause of hospital admissions in previously well infants in developed countries. There are no data on its prevalence in developing countries. Since Chanock & Finberg identified respiratory syncytial virus (RSV) in 19571 the epidemiological aspects of AVB have been well studied. The classical clinical picture of an upper respiratory infection followed by wheezing, rapid respirations and chest retractions in infants is well recognised. AVB
AETIOLOGY
RSV is the main etiological agent of AVB but other viruses such as adenovirus, parainfluenza, influenza and Mycoplasma pneumoniae may also be responsible. Epidemic RSV occurs in the Northern Hemisphere from November to March but in high temperature areas the RSV season is not as well defined and may happen during the summer.
RSV is a common cause of hospital-acquired infection. Children admitted to hospitals, especially those with AIDS and other immunodeficiencies may shed the virus for long
RISK FACTORS
In developed countries studies have suggested that premature babies, infants under 6 months old, those with low birth weight, immunodeficiencies, congenital heart disease and cystic fibrosis are more prone to severe symptoms, high morbidity and greater mortality. However, there is little data on morbidity or mortality in infants from developing countries. In a study in Porto Alegre, Southern Brazil, some characteristics of admitted infants were worse than those expected in developed countries
PATHOLOGY AND IMMUNE ASPECTS
The initial abnormalities are necrosis of the respiratory epithelium with destruction of ciliated epithelial cells followed by peribronchial infiltration with lymphocytes. There is submucosal oedema and obstruction of the bronchioles by cellular debris and fibrin. This results in obstruction of the bronchioles with areas of atelectasis. In severe disease the obstruction causes mismatch of ventilation–perfusion that may progress to ventilatory failure.9
Some viruses cause different types of
DIAGNOSIS
As L.E. Holt described more than a century ago the diagnosis of AVB is made in infants presenting with a viral upper airway infection (coryza, fever, nasal congestion) followed by cough, tachypnoea and signs of respiratory distress (Holt (1897) as quoted by Hogg (1986)13). The detection of RSV, adenovirus, parainfluenza or influenza virus in the nasal secretion may help to confirm the clinical diagnosis. This identification may be by immunofluorescence, by enzyme-linked immunoabsorbent assays
TREATMENT
Oxygen is still the main treatment for this condition, as was stated by Reynolds & Cook in the early 1960s.17., 18. Inspiratory concentrations of oxygen from 28 to 35% usually correct the hypoxaemia.9 The use of a pulse oxymeter may be the only monitoring necessary in mild disease.15 It is important to monitor fluid balance in moderate and severe disease.19
Bronchodilator therapy does not change the natural history or progression of the disease.20., 21., 22., 23., 24. There is no good evidence
PREVENTION
Vaccination to prevent RSV is not yet available. Recently RSV immunoglobulin became available and proved to be cost-effective in selected patients.26., 27. Unfortunately it is very expensive to use in developing countries, as was suggested in a cost-effective analysis study from Argentina.28
Tobacco exposure may affect the severity of AVB. Avoiding tobacco exposure in infants may reduce the risk of severity.29
SEQUELAE OF VIRAL ILLNESSES IN EARLY LIFE IN DEVELOPING COUNTRIES
In a clinical study at the Respiratory Disease Centre of the Children’s Hospital, Buenos Aires,30 we evaluated 40 infants with a history of recurring bronchial obstruction. The mean age when the first episode occurred was 6 months. The children had an average of four events before they developed wheezing. A total of 75% had no risk factors for asthma (family history of asthma/atopic disease or exposure to cigarette smoking). All children underwent pulmonary function testing and, according to
PRACTICE POINTS
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Acute viral bronchiolitis (AVB) is the main reason for hospital admission in previously well infants.
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Management is supportive – hydration and oxygen therapy are the main forms of treatment.
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Systemic steroids and antibiotics are not indicated.
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Prevention of hospital infection is very important. Simple measures such as careful hand washing play an important role.
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Repiratory syncytial virus (RSV)-immunoglobulin is effective in selected patients but is extremely expensive.
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Adenovirus is the most
RESEARCH DIRECTIONS
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Prognostic factors in acute viral bronchiolitis (AVB) in developing countries.
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Studies on cost-effectiveness of respiratory syncytial virus (RSV)-immunoglobulin in developing countries.
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Define risk factors for bronchiolitis obliterans.
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Define risk factors that determine the course of bronchilitis obliterans.
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