MINI-SYMPOSIUM: RESPIRATORY PROBLEMS IN THE DEVELOPING WORLD
Acute viral bronchiolitis and its sequelae in developing countries

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Abstract

Acute viral bronchiolitis (AVB) is a common disease found throughout the world. Various aspects of it are being studied: its epidemiology, diagnosis, prognosis and treatment. Most of these studies are being conducted in developed countries, with only a few taking place in developing countries. Risk factors such as poor nutrition, an adverse environment and early weaning should be studied where these features are common. Treatment aspects such as cost-effectiveness in low income settings need further study. Use of ribavirin and respiratory syncytial virus (RSV)-immunoglobulin are good examples.

Post-bronchiolitic sequelae also need to be studied in low income countries. There is evidence that bronchiolitis obliterans is unusually frequent in some Latin-American countries such as Argentina and Brazil. It will be helpful to undertake combined studies in countries with the same socio-economics, investigating the preventive and management aspects of AVB and its sequelae to reduce the morbidity and mortality.

Section snippets

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

  • Acute viral bronchiolitis (AVB) is the main reason for hospital admission in previously well infants.

  • Management is supportive – hydration and oxygen therapy are the main forms of treatment.

  • Systemic steroids and antibiotics are not indicated.

  • Prevention of hospital infection is very important. Simple measures such as careful hand washing play an important role.

  • Repiratory syncytial virus (RSV)-immunoglobulin is effective in selected patients but is extremely expensive.

  • Adenovirus is the most

RESEARCH DIRECTIONS

  • Prognostic factors in acute viral bronchiolitis (AVB) in developing countries.

  • Studies on cost-effectiveness of respiratory syncytial virus (RSV)-immunoglobulin in developing countries.

  • Define risk factors for bronchiolitis obliterans.

  • Define risk factors that determine the course of bronchilitis obliterans.

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