"Infectious disease condemns poor countries to an endless cycle of ill health and poverty. Now a powerful new model of the link between disease and economic growth has revealed why some escape plans work while others just make matters worse. The problem is that when workers suffer from poor health, economic output goes down. And if economic output goes down, there is less to spend on healthcare. And if spending on healthcare drops, workers become less healthy. And so on. So an obvious solution is for a country to spend more on healthcare. But the new model says governments must take care since the cost to a poor country can send the economy spiraling into long term decline. By contrast, an injection of capital from outside the country allows spending on healthcare to increase without any drop in economic output. 'We find that a large influx of capital is successful in escaping the poverty trap, but increasing health spending alone is not,' say the authors. And the amount required is relatively little. The model suggests that long-term investment needs only to be more than 15 per cent of the cost of healthcare. But anything less than this cannot prevent the vicious circle of decline."