Malaria is killing more people worldwide than previously thought, but the number of deaths has fallen rapidly as efforts to combat the disease have ramped up, according to new research from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington.

More than 1.2 million people died from malaria worldwide in 2010, twice the number found in the most recent comprehensive study of the disease. IHME researchers say that deaths from malaria have been missed by previous studies because of the assumption that the disease mainly kills children under 5. IHME found that more than 78,000 children aged 5 to 14 and more than 445,000 people aged 15 and older died from malaria in 2010, meaning that 42% of all malaria deaths were in people aged 5 and older.

“You learn in medical school that people exposed to malaria as children develop immunity and rarely die from malaria as adults,” said Dr. Christopher Murray, IHME Director and the study’s lead author. “What we have found in hospital records, death records, surveys, and other sources shows that just is not the case.”

The study also found that while the overall number of malaria deaths is higher than earlier reports, the trend in malaria deaths followed a similar downward pattern. Starting in 1985, malaria deaths grew every year before peaking in 2004 at 1.8 million deaths worldwide. Since then, the number of deaths fell annually, and between 2007 and 2010, the decline in deaths was more than 7% each year.

The new findings are being published today in The Lancet in “Global malaria mortality between 1980 and 2010: a systematic analysis.” The work is part of the Global Burden of Diseases, Injuries, and Risk Factors 2010 Study. Other research from this study, global trends in child mortality, maternal mortality, breast cancer, and cervical cancer, were released last year, and more trends will be released in the coming months.

Researchers say the biggest drivers of the decline in malaria deaths have been the scale-up of insecticide-treated bed nets and artemisinin-combination treatments (ACTs). This has been accomplished through the advent of the Global Fund to Fight AIDS, Tuberculosis and Malaria in 2001 and the creation of organizations focused on fighting malaria, such as the World Health Organization’s Roll Back Malaria, Malaria No More, and Nothing But Nets. Overall funding for malaria efforts grew from less than $0.25 billion annually in 2001 to more than $2 billion in 2009, according to IHME’s latest estimates. IHME reported in September 2011 that homes owning at least one bed net were associated with a 23% reduction in child mortality.

“We have seen a huge increase both in funding and in policy attention given to malaria over the past decade, and it’s having a real impact,” said Dr. Alan Lopez, Head of the School of Population Health at the University of Queensland and one of the study’s co-authors. “Reliably demonstrating just how big an impact is important to drive further investments in malaria control programs. This makes it even more critical for us to generate accurate estimates for all deaths, not just in young children and not just in sub-Saharan Africa.”

One of the most important factors in identifying the new malaria estimates was the use of verbal autopsy data. In a verbal autopsy, researchers interview the relatives of someone who has recently died to identify the cause of death. IHME and collaborators around the world published a series of articles in a special edition of Population Health Metrics in August 2011 focused on advancing the science of verbal autopsy. Verbal autopsy data were especially important in India, where malaria deaths have been vastly undercounted in both children and adults. IHME found that more than 37,000 people over the age of 15 in India died from malaria in 2010, and the chances of someone dying from malaria in India have fallen rapidly since 1980.

Progress in fighting malaria can be seen everywhere. Countries such as Zambia and Tanzania saw malaria deaths fall by more than 30% between 2004 and 2010. The progress being seen in Africa is especially significant, given that malaria deaths there accounted for a quarter of all deaths in children under 5 in 2010.

But the researchers warn that those gains could be reversed if global economic troubles continue to stifle funding efforts. IHME reported in December that growth in development assistance for health slowed greatly between 2009 and 2011. The announcement by the Global Fund in November that it would cancel its next round of funding casts a cloud over the future of malaria programs, the researchers say.

“If the Global Fund is weakened, the world could lose 40% of all the funding dedicated to fighting malaria,” said Dr. Stephen Lim, Associate Professor of Global Health at IHME and a co-author on the study. “That kind of loss of funding poses a definite threat to the health of people in countries with a high malaria burden, which in many cases are some of the poorest countries in the world. We need to think of ways to fill funding deficits in order to ensure continued progress on malaria mortality.”