13. Upper respiratory tract infections
The upper respiratory tract is the initial site of infection or a site of colonization for most infections of the respiratory tract (Fig. 3.13.1). It is also the site for a number of resident organisms, the prevalence of which will vary in individuals:
common: Streptococcus mutans and other α-haemolytic streptococci, Neisseria sp., corynebacteria, Bacteroides spp., Veillonella spp., other anaerobic cocci, fusiform bacteria, Candida albicans, Haemophilus influenzae, Entamoeba gingivalis
less common: Streptococcus pyogenes, Streptococcus pneumoniae, Neisseria meningitidis, Staphylococcus aureus.
Some of these resident flora can be pathogenic. Infections of the upper respiratory tract (URTIs) are the commonest acute illness. The respiratory tract has defence mechanisms that prevent infection in the normal individual (Fig. 3.13.2). The mucociliary escalator is the process where the mucous lining of the tract is swept upwards by the beating of cilia, thus carrying foreign particles trapped in the mucus up towards the pharynx, where it is swallowed.
Common colds/rhinitis
Children suffer two to six colds per year in industrialized countries, with this frequency halving in adulthood. This high incidence of colds is attributable to the high number of viruses and serotypes involved. Both aerosol and fomite transmission contribute to the spread of infection.
The principal findings of rhinorrhoea and sneezing are found in almost all cases. In addition, there may be sore throat, headaches and constitutional upset with fever. Earache is frequent in childhood. The diagnosis of the syndrome is clinical; laboratory identification is not required because of the current absence of appropriate antiviral therapy. Antirhinoviral therapy is, however, a possibility as drugs are developed that block the interaction between the major host cell receptor (intercellular adhesion molecule-1) and the virus receptor-binding protein in a canyon that occurs on the surface of the viral capsid. Symptomatic therapy with analgesics and decongestants is commonly employed. Vaccine development is hindered by the diverse aetiology.
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