To better understand acquired immunity to respiratory-syncytial-virus infections, we analyzed data from a 10-year study of respiratory illness in normal children who were followed longitudinally from early infancy. Immunity was measured in terms of failure to become infected or reduction in severity of clinical illness upon reinfection. Outbreaks of infections occurred seven times over the 10-year-period. During epidemics the attack rate for first infection was 98 per cent. The rate for second infections (75 per cent) was modestly reduced (P less than 0.001); that for third infections was 65 per cent. Age and history of infection both influenced illness. Immunity induced by a single infection had no demonstrable effect on illness associated with reinfection one year later; however, a considerable reduction in severity occurred with the third infection. These observations suggest that amelioration of illness--rather than prevention of infection--may be a realistic goal for immunoprophylaxis.

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We analyzed data from a 14-year longitudinal study of respiratory infections in young children to determine the relative importance of viral respiratory infection and nasopharyngeal colonization with Streptococcus pneumoniae and Haemophilus influenzae as factors influencing the occurrence of acute otitis media with effusion. The incidence of this disorder was increased in children with viral respiratory infections (average relative risk, 3.2; P less than 0.0001). Infection with respiratory syncytial virus, influenza virus (type A or B), and adenovirus conferred a greater risk of otitis media than did infection with parainfluenza virus, enterovirus, or rhinovirus. Colonization of the nasopharynx with Str. pneumoniae or H. influenzae had a lesser effect on the incidence of the disease (average relative risk; 1.5; P less than 0.01). Infections with the viruses more closely associated with acute otitis media (respiratory syncytial virus, adenovirus, and influenza A or B) were correlated with an increased risk of recurrent disease. Prevention of selected otitis-associated viral infections should reduce the incidence of this disease.

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During 1994 and 1995, an increase in the number and severity of group A streptococcal (GAS) infections was noted in North Carolina. Ninety-six patients had GAS recovered from blood and other sterile body fluids, abscesses, and soft tissue. The overall case fatality rate was 11% but was much higher in patients with toxic shock syndrome (55%) and necrotizing fasciitis (58%). Recent invasive GAS isolates were compared with pre-1994 invasive isolates and temporally related pharyngeal isolates by M protein serotyping, pulsed field gel electrophoresis (PFGE), and polymerase chain reaction amplification of the streptococcal pyrogenic exotoxin A gene. Serotypes M1 and M3 accounted for 50% of recent invasive isolates (1994-1995) and 58% of pharyngeal isolates (1994). The latter isolates demonstrated PFGE patterns that were identical to invasive M1 and M3 strains, suggesting that pharyngeal infections may have served as a reservoir for virulent GAS clones.

We conducted a randomized controlled trial to determine whether a home-based intervention program could reduce infant passive smoking and lower respiratory illness. The intervention consisted of four nurse home visits during the first 6 months of life, designed to assist families to reduce the infant's exposure to tobacco smoke. Among the 121 infants of smoking mothers who completed the study, there was a significant difference in trend over the year between the intervention and the control groups in the amount of exposure to tobacco smoke; infants in the intervention group were exposed to 5.9 fewer cigarettes per day at 12 months. There was no group difference in infant urine cotinine excretion. The prevalence of persistent lower respiratory symptoms was lower among intervention-group infants of smoking mothers whose head of household had no education beyond high school: intervention group, 14.6%; and controls, 34.0%.

Acute respiratory infections are the most frequent illnesses of the human host. Most infections are caused by viruses and bacteria; the proportion caused by viruses is much greater. The viruses most frequently involved are adenoviruses, influenza viruses, parainfluenza viruses, respiratory syncytial viruses, and rhinoviruses. Acute respiratory infections are more common in young children, have rather specific seasonal occurrences, and some agents are associated with specific respiratory syndromes. Risk factors associated with increased incidence or severity of respiratory infections are occurrence in the very young or the elderly; crowding; being male; inhaled pollutants; anatomic, metabolic, genetic or immunologic disorders; and malnutrition, including vitamin or micronutrient deficiency. Respiratory infections are a much greater problem in developing countries than in developed countries and are the leading causes of death in children under 5 yr of age. The same agents cause infections, and the incidence of total respiratory infections is the same as in the developed countries. The precise causes of increased morbidity and mortality in the developing world are unclear, but crowding, inhaled pollutants, and malnutrition are likely candidates. The interactive role of viruses and bacteria is not clear but may play a role in increased severity of respiratory infections.