Vaccination

The effect of vaccination against the serotypes responsible for pneumococcal otitis media has now been demonstrated, although further trials are essential. The use of influenza A and B vaccine in infants and young children remains controversial. Recent American studies found that, during years when influenza viruses predominate, the rates of hospitalisation with acute respiratory disease in children under 2 years of age (without specific risk factors) were as high as 2% per annum. Consequently, it has been suggested that routine influenza vaccination be considered in all young children. A recent Japanese study found routine vaccination of schoolchildren caused a major reduction in mortality from influenza in the elderly. This confirms that children are the major disseminators of influenza, and routine annual influenza vaccination for children could become policy in the near future.

In children over the age of 1 year, it is possible to use the potent, selective inhibitors of influenza A and B virus neuraminidase. These agents, which can be taken either by inhalation or orally, have proven effective both in the treatment and prevention of household spread of influenza. These agents appear to be free of major adverse effects, and emergence of drug resistant strains of viruses has not been a problem. The role of these agents in the treatment and prevention of influenza virus infection will soon be clarified.

Croup (Laryngotracheobronchitis)

Croup is usually considered to exist in two forms:

• acute viral croup

• recurrent (or spasmodic) croup.

While these two conditions have a number of similarities, they are likely to be distinct entities. They have in common that they involve the larynx, trachea and bronchi and present with a typically barking cough. The cough is so typical it is usually referred to as a 'croupy' cough.

Acute viral croup

Acute viral croup is typically a disease of toddlers, being rare in the first 6 months of life and reaching a peak incidence of 5 cases per 100 children per year during the second year of life. Boys are affected more commonly than girls. Most children who get acute viral croup will only ever have one or two episodes. These episodes typically begin with the symptoms of an upper respiratory infection and progress to typical croup over 1-2 days. The most common viruses isolated from children with croup are parainfluenza virus type 1 (up to 50% in some series), parainfluenza virus type 3 (up to 20%) and respiratory syncytial virus (approximately 10%).

Clinical manifestations

As mentioned above, croup usually begins with signs and symptoms of an upper respiratory infection, including fever and rhinitis. A cough may be present. The typical barking croupy cough usually begins during the night or the early hours of the morning. As the disease progresses, stridor may be heard on exertion initally. If the subglottic obstruction progresses further, stridor may be heard at rest and an expiratory component may be heard. The typical cough continues to be heard. If the degree of obstruction continues to worsen, the stridor may become more difficult to hear and the child may become distressed and restless. Cough may be absent at this stage. The lack of stridor comes about because the amount of air moving through the obstructed airway is not sufficient to generate the noise.

The distress and restlessness are most likely to be due tohypoxia and signal impending complete respiratory obstruction.

The viral illness generally lasts 7-10 days, but the typical croupy cough usually only occurs on the first 2-3 nights.