Health and economic performance are interrelated. Infant mortality, child mortality, and life expectancy all correlate with rising income. In four random countries in which the average annual income ranged, in 1990, from $660, to $1,727, to $3,795, to $11,422, infant mortality ranged from 114, to 66, to 34, to 9 (per thousand). As income doubles, infant survival tends to rise proportionately, a trend reflected in other measures of health and of wealth.
Different health conditions impede development in characteristic ways. HIV/AIDS for example, destroys the lives of workers in their most productive years and orphans millions of children. This combined effect will damage societies for generations, while discouraging investment today.
Malaria's economic impact is more insidious, particularly where transmission is most intense. In contrast to HIV/AIDS, young children rather than working adults are most affected. Some 300 million people become ill with malaria each year, causing 1.5 million deaths, most of them small children. Children who survive malaria develop into relatively immune adults. But visitors to a malaria infested country, because they lack this immunity, share the risks borne by local children.
Precisely because malaria differs in this way from other infections, its economic harm is so huge. No other disease is so prevalent, so rooted in the landscape, and so asymmetrical in its effects on visitors and residents. Although it once protected people in tropical areas by scaring away colonial invaders, malaria now burdens those same people by scaring investors and other outsiders away.