Malaria kills 1.2 million people each year, more than twice as many deaths as previously thought, according to new research published in the Lancet.
However, according to the Institute of Health Metrics and Evaluation, which conducted the new research, efforts to combat the disease, both through drug treatments and prevention, have resulted in a decline in malaria-related deaths.
"This runs counter to most assumptions about the disease," said Dr. Stephen Lim, associate professor of global health at the Institute. "The good news, though, is that even though the overall number of deaths is higher, the trend is sharply downward."
Researchers also found that while many believe most malaria deaths occur in children under age 5, in fact, 42 percent of all malaria deaths occur in older children and adults.
Authors from the Institute collected data on malaria deaths over two decades, from 1980 to 2010. They found that 1.2 million people died of the disease in 2010; twice as many deaths as reported by the World Malaria Report released last year. The World Health Organization estimated that about 650,000 people worldwide died of the disease in 2010.
Researchers said the higher death tally is likely due to the fact that more reliable data became available.
Based on the new numbers, malaria deaths have fallen by 32 percent since 2004, dropping from 1.8 million deaths worldwide to 1.2 million in 2010.
"That's a massive decrease, and it appears to be the result of the huge scale-up in spending to fight malaria, especially by the Global Fund to Fight AIDS, Tuberculosis and Malaria," Lim said.
Malaria is caused by a parasite passed to humans through mosquito bites. The parasites then travel through the bloodstream to the liver and infect red blood cells, according to the National Institutes of Health.
The parasites multiply within the body, and then symptoms, including chills, fever, vomiting and coma, occur 10 days to four weeks after the mosquito bite occurs. If left untreated, complications can include kidney failure, liver failure, meningitis and, ultimately, death.
The disease is most prevalent in Africa, where, according to the World Health Organization, it is the cause of one in five childhood deaths. The Bill & Melinda Gates Foundation has spearheaded an effort to reduce malaria deaths to zero by 2015.
"Given these findings, that might be unrealistic," said Lim. Nevertheless he believes it will be possible to dramatically reduce the number of deaths, he said.
"This just adds to the urgency of meeting the audacious goal of the Bill & Melinda Gates Foundation, set in 2007 to eradicate malaria," said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine. "It also gives us pause to look at malaria... among adults."
To eradicate malaria, physicians need to start properly diagnosing malaria in all age groups, Lim said, and malaria-prone countries need access to drugs and proper equipment for treatment and prevention.
"We need to make sure the proper malaria control efforts are in place, including insecticide-treated bed nets," said Lim. "We found, for example, in a study last year that there is a 23 percent reduction in child mortality in homes that have a bed net."
"We also want to make sure that effective treatments… are available to both children and adults," he added.
A new class of drugs containing the compound artemsinin has been found to be effective and has replaced older drugs that were causing parasitic resistance. The disease can be easy to treat, but in places with limited access to up-to-date medical care and a short supply of effective drug therapy, death rates are higher.