Pathogens

Viruses cause 80–90% of childhood respiratory infections. The most important are the respiratory syncytial virus (RSV), rhinoviruses, parainfluenza, influenza, metapneumovirus and adenoviruses. An individual virus can cause several different patterns of illness, e.g. RSV can cause bronchiolitis, croup, pneumonia or a common cold.

The important bacterial pathogens of the respiratory tract are Streptococcus pneumoniae (pneumococcus) and other streptococci, Haemophilus influenzae, Moraxella catarrhalis, Bordetella pertussis, which causes whooping cough, and Mycoplasma pneumoniae. Dual infections, with two viruses or with a viral and bacterial pathogen, may occur. Mycobacterium tuberculosis remains an important pathogen globally. Some pathogens cause predictable epidemics, such as RSV bronchiolitis every winter.

Host and environmental factors

An increased risk of respiratory infection is associated with a range of factors relating to the environment and host:

The child’s age influences the prevalence and severity of infections (Fig. 16.1). It is in infancy that serious respiratory illness requiring hospital admission is most common and the risk of death is greatest. There is an increased frequency of infections when the child or older siblings start nursery or school. Repeated upper respiratory tract infection is common and rarely indicates underlying disease.

Classification of respiratory infections

Respiratory infections are classified according to the level of the respiratory tract most involved:

The common cold (coryza)

This is the commonest infection of childhood. Classical features include a clear or mucopurulent nasal discharge and nasal blockage. The commonest pathogens are viruses – rhinoviruses (of which there are over 100 different serotypes), coronaviruses and RSV. Health education to advise parents that colds are self-limiting and have no specific curative treatment may reduce anxiety and save unnecessary visits to doctors. Fever and pain are best treated with paracetamol or ibuprofen. Antibiotics are of no benefit as the common cold is viral in origin and secondary bacterial infection is very uncommon.

Sore throat (pharyngitis)

The pharynx and soft palate are inflamed and local lymph nodes are enlarged and tender. Sore throats are usually due to viral infection with respiratory viruses (mostly adenoviruses, enteroviruses and rhinoviruses). In the older child, group A β-haemolytic streptococcus is a common pathogen.

Tonsillitis

Tonsillitis is a form of pharyngitis where there is intense inflammation of the tonsils, often with a purulent exudate. Common pathogens are group A β-haemolytic streptococci and the Epstein–Barr virus (infectious mononucleosis). Group A β-haemolytic streptococcus can be cultured from many tonsils; however, it is uncertain why it causes recurrent tonsillitis in some children but not in others.

Although the surface exudates seen in infectious mononucleosis are reported to be more membranous in appearance compared to bacterial tonsillitis, in reality it is not possible to distinguish clinically between viral and bacterial causes. Marked constitutional disturbance, such as headache, apathy and abdominal pain, white tonsillar exudate and cervical lymphadenopathy, is more common with bacterial infection.

Antibiotics (often penicillin, or erythromycin if there is penicillin allergy) are often prescribed for severe pharyngitis and tonsillitis even though only a third are caused by bacteria. They may hasten recovery from streptococcal infection. In order to eradicate the organism to prevent rheumatic fever, 10 days of treatment is required, but this is not indicated in the UK where rheumatic fever is now exceedingly rare. In severe cases, children may require hospital admission for intravenous fluid administration and analgesia if they are unable to swallow solids or liquids. Amoxicillin is best avoided as it may cause a widespread maculopapular rash if the tonsillitis is due to infectious mononucleosis.

Acute infection of the middle ear (acute otitis media)

Most children will have at least one episode of acute otitis media (OM). This is most common at 6–12 months of age. Up to 20% will have three or more episodes. Infants and young children are prone to acute otitis media because their Eustachian tubes are short, horizontal and function poorly. There is pain in the ear and fever. Every child with a fever must have their tympanic membranes examined (Fig. 16.2a–d). In acute otitis media, the tympanic membrane is seen to be bright red and bulging with loss of the normal light reflection (Fig. 16.2b). Occasionally, there is acute perforation of the eardrum with pus visible in the external canal. Pathogens include viruses, especially RSV and rhinovirus, and bacteria including pneumococcus, non-typeable H. influenzae and Moraxella catarrhalis. Serious complications are mastoiditis and meningitis, but are now uncommon. Pain should be treated with an analgesic such as paracetamol or ibuprofen. Regular analgesia is more effective than intermittent (as required) and may be needed for up to a week until the acute inflammation has resolved. Most cases of acute otitis media resolve spontaneously. Antibiotics marginally shorten the duration of pain but have not been shown to reduce the risk of hearing loss (see Ch. 5). It is often useful to give the parents a prescription, but ask them to use it only if the child remains unwell after 2–3 days. Amoxicillin is widely used. Neither decongestants nor antihistamines are beneficial.

Recurrent ear infections can lead to otitis media with effusion (OME or glue ear or serous otitis media). Children are asymptomatic apart from possible decreased hearing. The eardrum is seen to be dull and retracted, often with a fluid level visible (Fig. 16.2c). Confirmation of otitis media with effusion can be gained by a flat trace on tympanometry, in conjunction with evidence of a conductive loss on pure tone audiometry (possible if >4 years old), or reduced hearing on a distraction hearing test in younger children. Otitis media with effusion is very common between the ages of 2 and 7 years, with peak incidence between 2.5 and 5 years. This condition usually resolves spontaneously. Cochrane reviews have shown no evidence of long-term benefit from the use of antibiotics, steroids or decongestants. Otitis media with effusion is the most common cause of conductive hearing loss in children and can interfere with normal speech development and result in learning difficulties in school. In such children insertion of ventilation tubes (grommets, Fig. 16.2d) can be beneficial, but there is evidence, again from Cochrane reviews, that adenoidectomy can offer more long-term benefit. It is believed that the adenoids can harbour organisms within biofilms that contribute to infection spreading up the Eustachian tubes. In addition, grossly hypertrophied adenoids may obstruct and affect the function of the Eustachian tubes, leading to poor ventilation of the middle ear and subsequent recurrent infections. In practice, children with recurrent URTIs and chronic glue ear that do not resolve with conservative measures undergo grommet insertion. If these problems recur after grommet extrusion, reinsertion of grommets with adjuvant adenoidectomy is usually advocated.

Sinusitis

Infection of the paranasal sinuses may occur with viral URTIs. Occasionally there is secondary bacterial infection, with pain, swelling and tenderness over the cheek from infection of the maxillary sinus. As the frontal sinuses do not develop until late childhood, frontal sinusitis is uncommon in the first decade of life. Antibiotics and analgesia are used for acute sinusitis in addition to topical decongestants. There is some recent evidence that the concurrent use of intranasal corticosteroids or antihistamines together with antibiotics hasten recovery.

Tonsillectomy and adenoidectomy

Children with recurrent tonsillitis are often referred for removal of their tonsils, one of the commonest operations performed in children. Many children have large tonsils but this in itself is not an indication for tonsillectomy, as they shrink spontaneously in late childhood.

The indications for tonsillectomy are controversial, and must be balanced against the risks of surgery, but include:

Like the tonsils, adenoids increase in size until about the age of 8 years and then gradually regress. In young children, the adenoids grow proportionately faster than the airway, so that their effect of narrowing the airway lumen is greatest between 2 and 8 years of age. They may narrow the posterior nasal space sufficiently to justify adenoidectomy. Indications for the removal of both the tonsils and adenoids are controversial but include:

Croup

With laryngotracheobronchitis, usually called croup, there is mucosal inflammation and increased secretions affecting the airway, but it is the oedema of the subglottic area that is potentially dangerous in young children because it may result in critical narrowing of the trachea. Viral croup accounts for over 95% of laryngotracheal infections. Parainfluenza viruses are the commonest cause, but other viruses, such as human metapneumovirus, RSV and influenza, can produce a similar clinical picture. Croup occurs from 6 months to 6 years of age but the peak incidence is in the second year of life. It is commonest in the autumn. The typical features are a barking cough, harsh stridor and hoarseness, usually preceded by fever and coryza. The symptoms often start, and are worse, at night.

When the upper airway obstruction is mild, the stridor and chest recession disappear when the child is at rest. The child can usually be managed at home. The parents need to observe the child closely for the signs of increasing severity. The decision to manage the child at home or in hospital is influenced not only by the severity of the illness but also by the time of day, ease of access to hospital and the child’s age (with a low threshold for admission for those <12 months old, due to their narrow airway caliber), and parental understanding and confidence about the disorder.

Inhalation of warm moist air is widely used but is of unproven benefit. Oral dexamethasone, oral prednisolone and nebulised steroids (budesonide) reduce the severity and duration of croup, and the need for hospitalisation.

In severe upper airways obstruction, nebulised epinephrine (adrenaline) with oxygen by facemask provides transient improvement. Close monitoring, along with the advice of an anaesthetist or intensivist, is imperative due to the risk of rebound symptoms once the effects of the epinephrine (adrenaline) diminish after about 2 h. Only a few children with croup require tracheal intubation since the introduction of steroid therapy. Some children have a pattern of recurrent croup, which may be related to atopy.

Bacterial tracheitis (pseudomembranous croup)

This rare but dangerous condition is similar to severe viral croup except that the child has a high fever, appears toxic and has rapidly progressive airways obstruction with copious thick airway secretions. It is caused by infection with Staphylococcus aureus. Treatment is by intravenous antibiotics and intubation and ventilation if required.

Acute epiglottitis

Acute epiglottitis is a life-threatening emergency due to the high risk of respiratory obstruction. It is caused by H. influenzae type b. In the UK and many other countries, the introduction of universal Hib immunisation in infancy has led to a >99% reduction in the incidence of epiglottitis and other invasive H. influenzae type b infections.

There is intense swelling of the epiglottis and surrounding tissues associated with septicaemia. Epiglottitis is most common in children aged 1–6 years but affects all age groups. It is important to distinguish clinically between epiglottitis and croup (Table 16.1), as they require quite different treatment.

The onset of epiglottitis is often very acute (see Case History 16.1), with:

In contrast to viral croup, cough is minimal or absent. Attempts to lie the child down or examine the throat with a spatula or perform a lateral neck X-ray must not be undertaken as they can precipitate total airway obstruction and death.

If the diagnosis of epiglottitis is suspected, urgent hospital admission and treatment are required. A senior anaesthetist, paediatrician and ENT surgeon should be summoned and treatment initiated without delay. The child should be transferred directly to the intensive care unit or an anaesthetic room, and must be accompanied by senior medical staff in case respiratory obstruction occurs. The child should be intubated under controlled conditions with a general anaesthetic. Rarely, this is impossible and urgent tracheostomy is life-saving. Only after the airway is secured should blood be taken for culture and intravenous antibiotics such as cefuroxime started. The tracheal tube can usually be removed after 24 h and antibiotics given for 3–5 days. With appropriate treatment, most children recover completely within 2–3 days. As with other serious H. influenzae infections, prophylaxis with rifampicin is offered to close household contacts.

Case History

16.1 Acute epiglottitis

This 5-year-old girl developed a severe sore throat, drooling of saliva, a high fever and increasing difficulty breathing over 8 h (Fig. 16.4a) Epiglottitis was diagnosed and her airway was guaranteed with a nasotracheal tube. Antibiotics were started immediately (Fig. 16.4b,c). She made a full recovery.

Whooping cough (pertussis)

This is a highly contagious respiratory infection caused by Bordetella pertussis. It is endemic, with epidemics every 3–4 years. After a week of coryza (catarrhal phase), the child develops a characteristic paroxysmal or spasmodic cough followed by a characteristic inspiratory whoop (paroxysmal phase). The spasms of cough are often worse at night and may culminate in vomiting. During a paroxysm, the child goes red or blue in the face, and mucus flows from the nose and mouth. The whoop may be absent in infants, but apnoea is a feature at this age. Epistaxis and subconjunctival haemorrhages can occur after vigorous coughing. The paroxysmal phase lasts 3–6 weeks. The symptoms gradually decrease (convalescent phase) but may persist for many months. Complications of pertussis, such as pneumonia, convulsions and bronchiectasis, are uncommon, but there is still a significant mortality, particularly in infants. Infants who have not yet completed their primary vaccination at 4 months are particularly susceptible. Infants and young children suffering severe spasms of cough or cyanotic attacks should be admitted to hospital and isolated from other children.

The organism can be identified early in the disease from culture of a per-nasal swab, although PCR is more sensitive. Characteristically, there is a marked lymphocytosis (>15 × 10⁹/L) on a blood count. Although erythromycin eradicates the organism, it decreases symptoms only if started during the catarrhal phase. Siblings, parents and school contacts may develop a similar cough, and close contacts should receive erythromycin prophylaxis, and unvaccinated infant contacts should be vaccinated. Immunisation reduces the risk of developing pertussis and the severity of disease in those affected, but does not guarantee protection. The level of protection declines steadily during childhood.

Summary

Clinical features

Coryzal symptoms precede a dry cough and increasing breathlessness. Feeding difficulty associated with increasing dyspnoea is often the reason for admission to hospital. Recurrent apnoea is a serious complication, especially in young infants. Infants born prematurely who develop bronchopulmonary dysplasia or with other underlying lung disease, such as cystic fibrosis or have congenital heart disease, are most at risk from severe bronchiolitis. The characteristic findings on examination (Fig. 16.5) are: