The headache starts in the morning, a blinding pain that cripples Bonisiwe Mathenjwa as she tackles the routine tasks of a poor single mother with three children at her river bank hut in northern KwaZulu-Natal. She doesn't need the body pains, fever and flushes, dizziness and diarrhoea that follow to know she's down with malaria - for the third time in eight months.

At first Mathenjwa, 28, avoids the local clinic, not wanting to leave the kids with their elderly grandmother and hoping that this time her body will thwart the disease. But she's desperately ill by the time she's rushed by ambulance to Mosvold Hospital in Ingwavuma, a small rural town tucked in a corner near Swaziland and Mozambique. It is three days later and a stream of lifesaving quinine drips into her veins as she lies exhausted, shaky and sweaty in a tatty pink nightdress on a bed she shares with a woman and baby in a crowded isolation ward. "I feel a bit better so I'm not frightened anymore," she whispers. "This time I thought I was going to die."

There are 20 women and children packed into a ward built for half their number in the years before the current malaria epidemic. South Africa has not seen the disease on this scale since the 1930s. Northern KwaZulu-Natal (KZN) is in the grip of a malaria scourge moving down from heavily infested southern Mozambique and the surrounding regions, where some areas report 70 percent infection rates.

The parasite is running rampant along the border and is on the march south towards Durban. Earlier this year, two-year-old Craig Paul from Sea Cow Lake died of malaria - the first death of someone who contracted the disease in Durban in half a century. Health authorities were sure that Craig was infected locally, most likely by a mosquito brought in by a traveller in their luggage. Malaria cases and deaths in South Africa have increased more than five-fold in as many years. In just the first three months of this year, there were 24000 reported cases. Malaria infections have risen even more sharply in KZN, where there were 27206 cases last year - double the 1998 number and seven times the 4117 infections of 1995. The prediction for KZN this year is more than 30000 infections.

Mpumalanga and the Northern Province, too, have experienced a big upsurge in the disease, especially in regions bordering neighbouring countries. Cases in those provinces soared from fewer than 2000 in the 1989-1990 malaria season to 9543 in Mpumalanga and over 11500 in the Northern Province last year. Thousands more South Africans will perish if the blood-red splashes warning against malaria continue to seep down African maps which are becoming eerily reminiscent of those of the mid-1900s, the darkest days of the disease. If the epidemic were allowed to spread totally unchecked, we could possibly find ourselves back at the level of malaria fatalities of November 1931 to June 1932, when more than 22000 people died in KZN, says Dr Brian Sharp, director of the National Malaria Research Programme (NMRP) of the Medical Research Council. But he is optimistic that the tide will be turned. "All the right policies are in place and we are confident that next season will see an arrest in the number of cases and a reduction in the geographical distribution of malaria." To try to turn the tide, the authorities in KZN have had to resort to a huge house-spraying programme with one of the most controversial pesticides in history - DDT.

The hut in sweltering Ndumu is empty. Mathenjwa's meagre possessions are piled outside, to avoid being contaminated by the clouds of DDT. A masked man in blue overalls is spraying DDT through a fan nozzle onto the hut's inside walls, thatch ceiling and eves. There, the insecticide will last for some nine months and repel the mosquitoes that have nearly claimed her life three times. "I want the spray," Mathenjwa tells me. "I don't want to be sick again and I'm worried about my children." The programme began in February, four years after DDT was withdrawn under pressure from environmental groups. It was discovered last December that malaria-bearing Anopheles mosquitoes had become resistant to the more environmentally-friendly insecticides that had been sprayed since 1996. The consequent resurgence of mosquitoes included even the virulent Anopheles funestus, which was eliminated 50 years ago.

South Africa, which in the 1940s was one of the first countries in the world to use DDT against malaria, is now among the first to re-introduce it. Experts and the government will resist attempts by northern countries, which have money and medicine but not malaria, to stop the anti-malarial use of DDT at the UN Environmental Programme treaty meeting this month in Johannesburg. Barry Bredenkamp, an NMRP researcher in Durban, says a ban would be disastrous. "DDT is extremely effective and cheap. The case for it being a medical hazard is unproven, and should have little environmental impact in the small quantities we are using it." Returning to DDT was controversial but essential, agrees Dave McGlew, a provincial health department spokesman. "Given the deteriorating malaria situation and the growing threat to human life, we had little choice but to opt for the most effective way of combating the disease." Sharp concurs. "DDT is the best we have available, but it is only an interim measure until a better solution is found." The health department has gone to a great deal of trouble to minimise the toxic effects of DDT, consulting with environmental bodies, scientists and poison experts to ascertain how, where and what concentrations to spray inside homes. Strict procedures are followed to avoid environmental contamination. "There is a very small chance of harming people or animals," says McGlew. Since February, KZN's malaria control unit has sprayed 241020 structures (mostly one-room homesteads). Already surveys show a reduction in the number of mosquitoes inside homes. DDT spraying is being supported by other methods, says Jotham Mthembu, malaria co-ordinator for KZN. One is a natural oily solution applied to still waters to kill off mosquito larvae. People are being randomly screened for the disease, and bed nets and coils are being distributed. "We're also running a major information and education campaign warning people of the dangers of malaria and how to prevent it."

Under the Lubombo Spatial Development Initiative South Africa, Mozambique and Swaziland are working together to thwart malaria. Dr Hervey Vaughan-Williams emerges from a consulting room at Mosvold Hospital. "I reckon at least half the people in here have malaria," he declares, striding through a packed outpatients hall. "The epidemic has gone through the roof. We've moved from seasonal to all-year malaria." He says monthly deaths are still in single figures, probably because some people are becoming immune. "But with malaria moving south to places where there is no resistance, there will be lots of severe cases. More people could die." Malaria experts are hoping that the mosquito that infected young Craig Paul in Durban was transported there and that the Anopheles species found in northern KZN are not migrating to the city. There are also concerns about the epidemic growing in Mpumalanga and the Northern Province, which are not yet using DDT, and spreading towards cities such as Pretoria.

Marlize Booman, geographic information systems officer for the Malaria Control Programme in Mpumalanga - where DDT spraying is about to begin - says it will not be a quick fix and it could be quite a few seasons before a decrease is seen. While the stopping of DDT spraying in South Africa in 1996 is largely responsible for the current epidemic, other factors are contributing. There have been several years of good rainfall and very hot weather, which created perfect conditions for mosquitoes. Also, since 1994 there have been far greater movements of people across South Africa's borders, especially from hard-hit Mozambique. The malaria-transmitting species can travel in from other countries in taxis or aircraft. The cheapest, malaria drug - chloroquine - is rapidly losing its effectiveness and in some parts of the world malaria is resistant to the four leading frontline drugs. South Africa is hoping soon to introduce a combination therapy, that includes a powerful anti-malarial drug developed by the Chinese, into the arsenal of weapons being used to fight the killer disease. Still, hopes are largely pinned on DDT to thwart malaria as it did half a century ago.