Australasian Science: Australia's authority on science since 1938

Double-take on Malaria Deaths

By Stephen Luntz

The battle against malaria has gained a whole new urgency following an estimate published in The Lancet that it kills almost twice as many people as previously recognised.

Total global mortality is fairly well-known, but estimates of the cause of death are often unreliable in countries where the health system is difficult to access. Dr Alan Lopez of the University of Queensland’s School of Population Health was part of a study using the verbal autopsy tool, whereby the family of those who have died report symptoms. “Verbal autopsy has been used for research purposes in a defined group, but not previously for monitoring population health,” Lopez says.

“Despite assumptions that mainly young children die from malaria, our study identified that 42% of malaria deaths occur in older children and adults,” Lopez says. While only 78,000 children aged 5–14 years are estimated to die from malaria, the study found 445,000 adults were killed by the parasite in 2010.

According to co-author Dr Christopher Murray of the University of Washington: “You learn in medical school that people exposed to malaria as children develop immunity and rarely die from malaria as adults. What we have found in hospital records, death records, surveys and other sources shows that just is not the case.”

Lopez is not sure why the immunity theory is not working, but says the findings make a case to redouble efforts at malaria control. Lopez says that estimates of deaths from the disease are unreliable before the early 1980s, and from 1985 the death rate grew as resistance evolved to front-line treatments such as chloroquine.

A combination of new treatments and the distribution of insecticide-impregnated bed nets has seen this trend reversing since 2004. Over the next 6 years annual deaths fell from 1.8 million to 1.2 million. “Malaria is now the fastest falling death worldwide,” Lopez notes. “We need to continue to scale up these programs.”

There has been a mixed response from the World Health Organisation. “They criticised our conclusions,” Lopez says, “but they also noted that our uncertainty estimates and theirs overlapped”. The uncertainty estimates are large, Lopez admits, partly because deaths are often caused by a combination of diseases.