INTRODUCTION
Bronchiolitis is defined by IAP as ’ A constellation of clinical
symptoms and signs including viral upper respiratory prodrome followed
by increased respiratory effort and wheeze in less than 2 year old
children’. Many virus cause bronchiolitis with Respiratory syncytial
virus being common. Epidemiology of RSV has many unusual
characteristics. They infect children nearly in first year of life with
the peak incidence in 2 – 8 months. Its is the only virus which cause
most severe respiratory disease in the first month of life when there is
antibodies from the mother.1 WHO estimated RSV burden
globally as 64 million cases and 1,50,000 deaths every year. Peak
incidence at 2-8 months of age. This is one of the common cause of
hospitalisation
Intensive care is needed for about 15% to 30% of RSV infections. Due
to respiratory failure , apnoea 7% to 21% of hospitalised patient
needs mechanical ventilation 2 . Some prospective
study have suggested that RSV infection predisposes to blood
eosinophilia and airway hyperreactivity leading to development of wheeze
Overproduction of cytokines released by helper 2 T lymphocytes is
responsible for illness especially interleukin 4 and 5. These are
responsible for wheeze.Interleukin 4 and 5 cause migration of eosinophil
and also increases IgE production. 3