Malaria Hits One In 12 Of World Population

By Steve Connor

10 March 2005
The Independent

More than half a billion people are suffering from malaria today, twice as many as scientists thought had been affected by one of the biggest killers in the developing world.

The new figures are the result of detailed research that gives the most accurate assessment yet of the disease that kills at least a million people a year. Scientists now believe there are about 515 million cases of malaria out of 2.2 billion people who are at risk - about a third of the world's population.

The discovery throws the slow progress of the world's fight against malaria into sharp relief.

In countries such as Malawi, malaria claims more lives each year than Aids, but attracts a fraction of the attention. Coachloads of overseas visitors come to view the Aids projects run by Médicins Sans Frontières in the country, but few are interested in malaria.

Malaria has never captured the public imagination as Aids has done, even though children are its chief victims. Malaria is old and Aids is new. Most important, malaria is not a disease that affects the West - except for those fortunate enough to holiday in the tropics - whereas Aids threatens us all. The scale on which the parasite, transmitted by the mosquito, kills is breathtaking. A new malaria map of the world suggests that the incidence of malaria in Africa is some 50 per cent higher than previous estimates by the World Health Organisation and up to 200 per cent higher for areas outside Africa, such as in south-east Asia.

Professor Robert Snow, of the Wellcome Trust Research Laboratories in Nairobi, Kenya, who led the study, warned that the true figures for the spread of malaria across the globe may even be higher than these latest estimates.

"We have taken a conservative approach to estimating how many attacks occur globally each year but even so the problem is far bigger than we previously thought," he said.

"Getting numbers right is important. Not knowing the size of the problem limits our ability to articulate how much money we need to tackle the problem - not knowing where the problem is located means you can't spend wisely," he said.

For 40 years chloroquine was the standard treatment for malaria. Patients swallowed a couple of pills at the onset of the fever and within 48 hours they would be better. It was safe, effective and cheap.

But over recent decades, a drug-resistant strain of malaria, Plasmodium falciparum, has been growing in Africa and now accounts for well over 90 per cent of cases. Surveys in east Africa show that almost two-thirds of patients given chloroquine and nearly half of those on its successor, sulfadoxine-pyrimethamine, have died. The only effective therapies are those based on artemesinin, a drug derived from a weed that grows wild in Africa and the Far East.

Six years ago the WHO set a target to halve the number of deaths by 2010, but instead the toll has risen by at least a quarter, and in some areas by as much as 50 per cent, because victims have not had the right drugs. Hundreds of thousands of children have died needlessly and the disease has gone virtually unnoticed in the West. Malaria has been a scourge of humanity since antiquity and although it is largely preventable with the use of mosquito nets and insecticides it remains one of the biggest killers of children under five.

The disease, caused by a blood parasite transmitted in a mosquito bite, was eradicated from industrialised countries of the northern hemisphere about half a century ago but it still threatens some 40 per cent of the world - mostly in the poorest countries of Africa, South America and southern Asia.

More than 80 per cent of malaria deaths occur in sub-Saharan Africa and the WHO estimates that every day the disease kills 3,000 children. Those that survive often suffer brain disease or paralysis. Economists for the United Nations have identified malaria as one of the top four causes of poverty with many African governments spending up to 40 per cent of their total health budgets on the medical care or control of malaria.

In Africa alone the total economic burden of malaria is estimated at $12bn (£6.7bn) a year, according to the WHO.

The deadliest form of malaria is the single-cell parasite Plasmodium falciparum and the latest estimates of its spread suggest that there are more cases in south-east Asia than previously suggested.

"Our work has demonstrated that nearly 25 per cent of worldwide cases occur in south-east Asia and the western Pacific, whereas most people regard Plasmodium falciparum as a problem particular to Africa," Professor Snow said.

In 1998, the WHO produced estimates of the extent of malaria based on reports of cases compiled by individual countries and data on the intensity of transmission within a particular region. However, it is widely accepted that the two methods are flawed because many cases of malaria are not reported to the authorities and transmission rates can vary widely because of local factors such as the weather.

The new study uses a more proactive approach with a combination of epidemiological, geographical and demographic data. "We have taken a science-driven approach to working out who is at risk, where they are located and what their chances would be of developing an attack of malaria," Professor Snow said.

©2005 Independent News & Media (UK) Ltd.