ACUTE RESPIRATORY INFECTIONS
Upper respiratory tract infections, mainly common cold and acute pharyngitis, accounted for 10.8% (27.5 million) of all visits to physicians in the United States in 1991.1 In 1–4-year-old children, otitis media is one of the most common reasons for visits to physicians, and accounted for an additional 2.7 million office visits.1 To diagnose and treat upper respiratory tract infections and otitis media costs billions of dollars. Furthermore, the diagnostic criteria for upper respiratory tract infections are often subjective and based on symptoms alone; because of this, treatment varies significantly from physician to physician.2
Pneumonia is a severe and common upper respiratory tract infection that remains a substantial cause of morbidity and mortality in adults and children. In Europe and North America, the annual incidence of pneumonia in children younger than five years is 34–40 cases per 1000; and in the developing world the incidence is several-fold higher.3 Worldwide more than two million children die of pneumonia annually.4
In children under five years of age, respiratory syncytial virus (RSV) has been described as the single most important cause of acute respiratory tract infections; and repeated RSV infections are common in all age groups.4 In elderly patients, RSV infection causes 10% of hospital admissions, 10% of which have fatal outcomes.5 (These values are similar for influenza.) Vaccines for RSV, although immunogenic, do not protect from subsequent infections. Monthly administration of RSV immune globulin is effective but cumbersome. Currently there are humanized monoclonal antibodies available to prevent infections caused by RSV.6
Streptococcus pneumoniae and Haemophilus influenzae are significant respiratory bacterial pathogens that are amenable to prevention and treatment, but the emergence of resistant strains have induced changes in the empirical treatment.7 The development of conjugated vaccines for S. pneumoniae and H. influenzae have increased the immunogenicity compared with previous polysaccharide vaccines.8 However, the vaccination coverage against these two pathogens is far from optimal, especially in adults.
Pertussis remains endemic in the United States despite routine childhood vaccinations for more than half a century, and high coverage levels in children for more than a decade. A primary reason for the continued circulation of Bordetella pertussis is that immunity to pertussis wanes approximately 5–10 years after childhood pertussis vaccination is completed; this leaves adolescents and adults susceptible.9 Before 11–12-year olds were routinely vaccinated against diphtheria and tetanus, a number of developed countries suffered a reemergence of pertussis cases and outbreaks.
Diphteria is currently considered a rare infectious disease but remains a matter of concern both for travelers to countries where this infection is still active or from cases imported from endemic regions.10 Giving vaccination boosters containing diphtheria toxoid to adolescents and adults remains an important measure to prevent sporadic cases of respiratory diphtheria.
Finally, governments and hospitals must be prepared to fight outbreaks of ...