Epidemiology of acute respiratory tract infections, especially those due to Haemophilus influenzae, in Papua New Guinean children.

Acute lower respiratory tract infections (ALRI) are the most common cause of death in Papua New Guinean children. Haemophilus influenzae and Streptococcus pneumoniae are almost universally carried in the nasopharynx from a young age and commonly cause disease. While most H. influenzae isolates from blood and cerebrospinal fluid are serotype b, other serotypeable and nonserotypeable H. influenzae are more frequently isolated in Papua New Guinea than in developed countries. Low levels of antipneumococcal antibody, malnutrition, and upper respiratory carriage of invasive pneumococcal serotypes are associated with increased risk of ALRI. An oral H. influenzae vaccine given to adults with chronic bronchitis reduced the bacterial load in sputum and may thereby help reduce transmission of bacteria in the community. The efficacy of conjugate H. influenzae type b vaccine in preventing pneumonia must be determined in developing countries; vaccines against other types of H. influenzae will also be needed to control pneumonia and meningitis.