Acute Respiratory Infections Are the Leading Cause of Death in Children in Developing Countries

A paper by Hazlett et al. is of particular importance because it addresses the question of the role of acute respiratory infections (ARI) as a cause of morbidity and especially mortality in 3rd world children. Diarrheal disease and malnutrition are generally thought to be the major killers of these children, and until recently little attention was paid to ARI. Recent data suggest that ARI are more important than realized previously and almost certainly are the leading cause of death in children in developing countries. It is estimated that each year more than 15 million children less than 5 years old die, obviously most in socially and economically deprived countries. Since death usually is due to a combination of social, economic, and medical factors, it is impossible to obtain precise data on the causes of death. It has been estimated that 5 million of the deaths are due to diarrhea, over 3 million due to pneumonia, 2 million to measles, 1.5 million to pertussis, 1 million to tetanus, and the other 2.5 million or less to other causes. Since pertussis is an acute respiratory infection and measles deaths frequently are due to infections of the respiratory tract, it is becoming clear that ARI are associated with more deaths than any other single cause. The significance of this is emphasized when the mortality rates from ARI in developed and underdeveloped nations are compared. Depending on the countries compared, age group, and other factors, increases of 5-10-fold have been reported. These factors raise the question of why respiratory infections are so lethal for 3rd world children. The severity of pneumonia, which is the cause of most ARI deaths, seems to be the big difference. Data are accumulating which show that bacterial infections are associated with the majority of severe infections and "Streptococcus pneumoniae" and "Haemophilus influenzae," infrequent causes of pneumonia in developed world children, are the microorganisms incriminated in a large proportion of cases. The increase in severity of ARI in 3rd world children has been associated, at least in port, with malnutrition, diarrheal diseases, an increased parasite load, and more recently with air pollution. Crowding and other factors associated with poverty doubtless also play a role. How these various factors contribute to increased severity and lethality is not well understood. The increasing recognition of the important role played by ARI as causes of mortality in 3rd world children is encouraging. The UN International Children's Emergency Fund (UNICEF) has joined the World Health Organization in the battle against ARI in developing countries, and the 2 organizations recently issued a joint statement on the subject in which they pledged to collaborate to integrate an ARI component into the primary health care program.