Epidemiology of acute respiratory infections

Nearly 25% of all deaths among children less than 5 years of age in developing countries are caused by acute respiratory infections (ARI). Estimates of annual mortality rates for ARI in infants range from 1.5 per 1,000 in North America to from 11 to 15 in 1,000 per Central and South America and Africa. Annual mortality rates for ARI for children 1 to 4 years of age ranged from 0.08 per 1,000 in North America to 1 to 1.5 per 1,000 in Central and South America and in Asia to nearly 5 per 1,000 in Africa. The economic consequences of even relatively benign ARI are substantial. In the United States, consumers spend about $2 billion per year for over-the-counter medications for ARI, and the total annual cost of ARI managed in outpatient settings is estimated to be more than $10 billion. There has been substantial variation both in the definitions of ARI and in methods of surveillance for ARI in various studies. Despite this, in most studies, infants and young children had 6 to 8 episodes per year of ARI. Although the frequency of ARI was similar in both developed and developing countries, the case-fatality rate is much higher in developing countries. It may be possible to prevent some of these serious infections with new vaccines against important causes of ARI in children (or with better distribution of currently available vaccines).