Beefed-up investments in malaria control are having a major impact, according to the new World Malaria Report, released yesterday by the World Health Organization (WHO). But the report also demonstrates just how fragile the gains are: Three African countries that have recorded some of the most impressive progress—Rwanda, Zambia, and São Tomé and Príncipe—saw malaria cases rise again in 2009.
First, the good news: Funding for malaria control has exploded the past few years, up from less than $200 million in 2004 to about $1.8 billion in 2010. As a result, an estimated 42% of African households owned at least one insecticide-treated bed net by mid-2010; about 35% of children were estimated to sleep under one. In addition, indoor spraying of insecticides to kill the malaria-transmitting mosquitoes is now provided for about 10% of people at risk. Eleven African countries (and 32 outside of Africa) have seen a 50% or greater reduction in malaria cases during the past decade. Worldwide deaths in 2009 are estimated to number 781,000—about 200,000 fewer than the estimate for a decade ago.
"The results set out in this report are the best seen in decades," WHO Director-General Margaret Chan said yesterday during a press conference in Geneva, Switzerland. Because the data don't go beyond 2009, WHO has little or no evidence of progress in 31 other African countries, including big ones like Nigeria and the Democratic Republic of the Congo, where bed nets have only recently been introduced on a large scale. Malaria declines in those stragglers are widely expected in the years ahead, however.
But three countries where success came early provide a cautionary tale. In São Tomé and Príncipe, a tiny two-island island nation off the West African coast, bed net coverage was among the highest in Africa as early as 2007, and the majority of the population was also protected using indoor spraying between 2005 and 2007. Malaria deaths between 2005 and 2008 were a stunning 86% lower than in the previous 4 years. (The country has embarked on a program to eliminate the disease entirely, although it does not yet meet WHO criteria for either the elimination of pre-elimination phase.) But in 2009, malaria roared back, with a 140% increase in cases and a 44% rise in deaths compared with 2008. That may have been in part because no spraying was undertaken in 2008, says the report; an emergency round of spraying brought the numbers back down in 2009.
Zambia's success story meanwhile—where malaria had been on the decline since 2001—began to unravel in 2009 with a major resurgence in the Eastern and Luapula provinces. The reasons aren't quite clear; in Luapula Province, bed net coverage declined, but it remained high in Eastern Province, says WHO's Richard Cibulskis, the report's main author; perhaps the fact that the nets are too old now is the problem, he says.
Aging nets may also be the reason that Rwanda, another front-runner in terms of bed net coverage, saw an upswing late in 2008 and 2009, after a period of dramatic success. "It's worrying that malaria can come back as soon as we take our foot off the accelerator," says Cibulskis.
The findings show that malaria prevention tools are a bit like vaccines, says epidemiologist Simon Hay of the University of Oxford in the United Kingdom: You have to keep applying them at high levels to keep the disease down. Malaria-endemic countries find it tough to stay vigilant once the numbers plummet, says Hay--and so do the developed countries that pay the bills. "Many donors seem to think that you buy the nets for a country, the disease goes down, and then it's over," says Hay. "But you can never relax."
WHO recommends that so-called long-lasting insecticide-treated nets be replaced after 3 years. That means that millions of nets introduced in 2006 and 2007 should be replaced now--with many more due for replacement in the years ahead.
Rwanda, for one, has begun replacing nets in 2010, says Cibulskis. But it's perhaps an even bigger challenge than introducing the first generation of nets, he says, because for donors "it's less spectacular" to support a program that maintains, rather than achieves, such stunning successes.