But as the numbers taking ART started to climb, doctors began noticing a second, hidden epidemic: tuberculosis (TB).

Patients being treated for Aids were still dying of tuberculosis in large numbers.

Worse, the raging HIV/Aids epidemic seemed to have masked the growing tuberculosis problem.

Tuberculosis resurgent

Once on the wane, tuberculosis is again resurgent, especially in countries facing major HIV/Aids epidemics.

In 2006, it killed an estimated 1.7 million people, according to the UN. An estimated two million died of HIV/Aids, but for many the immediate cause was tuberculosis; TB is the number one killer for people with Aids.

Unlike Aids, TB - once known as the white plague - is a curable disease, but proper treatment is complicated and requires at least a six-month course of antibiotics.

However, HIV attacks the immune system, making people more susceptible to infections like TB, and as a result, there are high-levels of co-infection.

At Helen Joseph Hospital, for example, more than 90 per cent of patients admitted to hospital wards for TB were also HIV-positive.

Of all patients diagnosed with TB, 65 per cent are also HIV-positive.

As South Africa focused on combating HIV/Aids, its tuberculosis rates quietly soared. The country now has one of the worst epidemics in the world.

By 2006, the TB incidence rate in South Africa - the number of new cases each year - had become the second highest in the world, a staggering 940 cases per 100,000, according to the World Health Organisation (WHO).

Only neighbouring Swaziland, another Aids-stricken country with a population of just over a million, has a higher rate.

'HIV driving TB'


In South Africa, as in many of the African countries were HIV/Aids is widespread and tuberculosis resurgent, completion rates for tuberculosis treatment have fallen in recent years.

Only about 70 per cent of people successfully finish their treatment. The rest die or stop taking their drugs. Many more are never even identified as being infected.

The poor quality of TB treatment costs lives but is also causing the rise of dangerous new strains of drug resistant tuberculosis.

Doctors are increasingly worried about multidrug-resistant tuberculosis (MDR-TB), which is resistant to the two most powerful drugs used to treat the disease.

Globally there were half a million new cases of MDR-TB last year, about five per cent of all new tuberculosis cases. But HIV-positive people are twice as likely to be infected with resistant strains, and are more likely to die if they are.

Even more alarming for many health care professionals is the recent emergence in South Africa's KwaZulu-Natal province of a deadly strain of tuberculosis that is virtually untreatable with known drugs.

Struggling to diagnose

South Africa is struggling to even properly diagnose MDR-TB.

At Helen Joseph, for example, tests for TB are returned from the laboratory in less than 24 hours. But it can take up to two months to determine whether someone is infected with MDR-TB.

By then, the patient is often dead or has disappeared. They have also had months to spread the resistant strain to other people.

Dr. Louisa Ferreira, who runs the paediatric ward at Soweto Hospice, says she is seeing an increasing number of MDR-TB cases in her own small ward and in local hospitals.

For now, TB is still in the shadow of HIV/Aids, but she and others say the threat it poses is enormous.

She said: "It may be bigger than HIV."



Al Jazeera