Much could be done about these three deadly diseases, but it requires money and political will from the rich countries. Some of the interventions are cheap. Infectious diseases rarely kill anyone in rich countries. Modern medicine stamped out the terror of tuberculosis, while good food and sanitation now enable us to resist potentially dangerous bugs, and if they do slip past our defences then we have antibiotics to destroy them.
Germs that used to wipe out large numbers of children now hold no fear, thanks to vaccination. But health for the rich is a world away from health for the poor. Infectious diseases are responsible for half of all deaths in the developing world. The three horsemen of the apocalypse ride through Africa and Asia and their names are HIV/Aids, TB and malaria. Between them, they cause 300m illnesses and more than 5m deaths every year. Aids is turning back the clock, unpicking the economic and social development that had been hard won in many sub-Saharan nations, decimating a generation in their twenties and thirties who were the workers, teachers and parents.
In Botswana, where HIV infection is now running at 39% of the population, average life expectancy has dropped to 37 from a high of 62 in the 1980s. The sub-Saharan average life expectancy is now 47. In a very real way, these are diseases of poverty. Malaria and TB are endemic only in the developing world now, but HIV/Aids is an incurable infection lurking in the immune system of 900,000 people in the US and 34,000 in the UK. But while those in the rich world live with HIV/Aids, those in poor countries die of it. Lack of good nutrition and treatment for minor infections that their HIV-compromised immune systems cannot resist contribute to their early death.
The drugs that suppress the virus and keep people well in the affluent north are still too expensive for most of the 40 million infected throughout the world. TB and HIV have formed a deadly partnership. TB takes hold of those whose immune systems have been weakened by HIV and is the immediate cause of death in 15% of cases. Eight million people a year catch TB in the world and 2 million a year die.
The disease has been easily treated in the past with antibiotics, but strains that are resistant to the common drugs are spreading and threatening to become a European problem, incubating in Russia's prisons and travelling the world economy class. Malaria is a parasitic disease transmitted through the bite of the Anopheles mosquito, which was once widespread and even endemic in the UK, but now 90% of deaths occur in sub-Saharan Africa. It causes 1m deaths a year - mostly of young children - and 300m acute illnesses.
Many children who survive suffer learning impairments or brain damage. There are drugs for malaria, but the parasite has developed resistance to one after another. Chloroquine, the most widely used anti-malarial drug, is now almost useless in southern and eastern Africa, and sulfadoxine-pyrimethamine, known by the brand name Fansidar, is fast following suit. Much could be done about these three deadly diseases, but it requires money and political will from the rich countries.
Some of the interventions are cheap, such as the provision of insecticide-impregnated mosquito nets to prevent children being bitten during the night, which studies have shown can cut malaria deaths by 20%. But even the supply of medicines for HIV/Aids which are unaffordable to most who need them in sub-Saharan Africa would not cost the affluent north a fraction of the bill it pays for defence - and yet there have been plenty of warnings that Aids is a security issue. Children orphaned by Aids who grow up on the streets without teachers or hope are a terrorist army in embryo.
UN organisations believe that there is now a will on the part of the north to do something about the death toll and economic damage from disease. If they are right, it is the crisis over Aids that has changed the world's mood, the seminal moment being the court case in Pretoria in 2000 which pitted the giant drug companies against the South African government. The drug companies tried to block changes in the law to allow Pretoria to import cheap medicines. In the face of an international outcry, the drug companies eventually dropped the case. If there was a single moment that the world woke up to the tragedy of Aids, it was then.
The prices of anti-retroviral drugs that keep people with HIV alive in the north have been forced down in developing countries through the resulting generic competition, from about $10,000 a year for a three-drug cocktail to around $300. Most people believe they can and will come down further. Action Aid is one of the NGOs lobbying for tiered drug pricing - rock-bottom prices for poor countries subsidised by high prices in rich countries.
In principle, the EU governments appeared willing to put such a system in place, but, says Louise Hilditch, coordinator of Action Aid Alliance, little seems to be happening. "It is not problematic. All it means is different prices in different markets. The pharmaceutical industry is waiting for governments to move and governments aren't moving. There are good intentions, but it is all just too slow." There is money available to help poor countries buy medicines and improve the way they treat these diseases in the shape of the Global Fund for HIV/Aids, TB and Malaria. It was set up by the UN secretary-general, Kofi Annan, and is supposed to raise $7bn to $10bn a year from donors, but in just over a year it has received only $2.8bn.
The US has been widely condemned for putting in a mere $500m. It is true that there is more money going in than ever before, along with more political will, but infectious diseases will outstrip all the current efforts to keep them in check unless some of the fundamentals are tackled. Very little effort is going into finding new cures and treatments for these and other infectious diseases. In June, a paper in the Lancet spelled out the shocking imbalance. Between 1975 and 1999, out of 1,393 new medicines brought to market, only 16 were for tropical diseases and TB.
It was 13 times more likely that a new drug would be for cancer or a central nervous system disorder than for one of the diseases taking such a toll in poor countries. "Doctors in poor countries are forced to use old and ineffective treatments on patients who are dying from treatable diseases because profit, not need, is driving the development of new medicines," said Morten Rostrup, the international council president of Medecins Sans Frontieres, at a conference on diseases earlier this year.
"We have the scientific know-how to right this fatal imbalance, but serious political and financial commitment is lacking." Sleeping sickness killed 66,000 people in 1999 and threatens 60 million. By chance, a pharmaceutical company found a drug that worked on the later, deadly stages of the parasitic disease, called eflornithine. But in 1995, after just five years, production was stopped because African countries could not afford it.
A cream formulation continues in the US, however, where it is making a fortune . . . as a hair remover. Aventis, which held the licence in 1998, eventually passed it to the World Health Organisation, which has since been trying to secure a long-term production source. The market has clearly failed and will continue to fail the developing world's health needs. The hunt is on for new ways of researching, developing and funding the medicines that poor nations badly need.
The WHO and the UN are promoting public-private partnerships. The talk is of incentives to encourage drug companies to get involved. Developing countries also need help to build up a pharmaceutical industry of their own, with technology transfer from the middle-income nations such as Brazil who already do it well. The prospects look brighter than they have done for years, but that is still little more than a hopeful glimmer in the gloom of rampaging disease.