Bronchiolitis is an acute infectious disease of the lower respiratory tract that occurs primarily in those aged between 2 months and 2 years, especially young infants. It is usually due to a viral infection of the bronchioles. A combination of increased mucus production, cell debris and oedema produces narrowing and obstruction of small airways.

· Respiratory synctial virus (RSV) is the most common pathogen1

· Adenovirus (11%) - occasionally causes a similar syndrome with a more virulent course

· Parainfluenza virus

· Other less common causes include:

o      Enterovirus

o      enterovirus

o      Rhinovirus

o      Clamydia pneumoniae

· Peak incidence of RSV infections is in the winter months, although the size of the peak varies from winter to winter.1

· Incidence peaks in those aged 2-8 months.

Symptoms

· Early symptoms are those of a viral URTI, including mild rhinorrhoea, cough, and fever (50% will have a temperature >38.5 °C)

· For the 40% of infants and young children who progress to lower respiratory tract involvement, paroxysmal cough and dyspnoea develop within 1-2 days.

· Other common symptoms include the following fever, wheeze, cynosis, vomiting, irritability and poor feeding

· Apnoea may occur, especially in young infants

Signs

· General signs: tachypnoea, tachycardia, fever, cyanosis, may be dehydrated.

· Mild conjunctivitis, pharyngitis.

· Diffuse expiratory wheezing, nasal flaring, intercostal recession, inspiratory crepitations.