CAPE TOWN - African nations are failing to control tuberculosis and could be overwhelmed by drug resistant strains of the infectious lung disease, with dire implications for the war on AIDS, a leading AIDS activist said on Monday.

"The explosion of tuberculosis on the continent is combined with the explosion and advance of the HIV epidemic," Zackie Achmat, the head of South Africa's Treatment Action Campaign (TAC), told Reuters in an interview in Cape Town.

"We need new TB vaccines, new TB testing and we need new TB medicines," Achmat said as he and other activists prepared for a Nov. 8 march in the city that will champion a global call for a radical programme to attack TB.

Spread through close personal contact, TB has long been a problem in Africa, where hundreds of millions of people are latent carriers. But its growing relationship with HIV has made treating both diseases more difficult in vulnerable populations.

The emergence of extensively drug resistant TB (XDR-TB), a strain virtually immune to traditional and modern antibiotics, has raised alarm bells since surfacing in South Africa's KwaZulu-Natal Province and neighbouring Lesotho in 2006, where it killed up to 85 percent of those infected.

The majority of those who died also had HIV.

The strain has since spread to other parts of Africa as well as to the industrialised world.

The prospect of a more virulent TB epidemic sweeping through Africa -- where crowded shantytowns and fragile health systems help spread the infection -- is a more serious threat because the two diseases are so prevalent and interlinked in the region.

A third of the estimated 40 million HIV-positive people worldwide are believed to be co-infected with TB and HIV. In South Africa, 61 percent of the roughly 250,000 people diagnosed with TB each year have HIV.

HIV-positive people and others with weakened immune systems are particularly vulnerable to TB as well as other opportunistic infections. But XDR-TB has led to not only higher mortality rates but also much faster deaths in HIV-positive populations.

"If XDR-TB becomes widespread and endemic it's going to cost the health system a phenomenal amount, never mind the fact that it will lead to phenomenal loss of life," said Achmat, who added that richer, industrialised nations were also not doing enough to fight TB.

The march on Thursday coincides with the opening of an international lung health conference, where experts are expected to discuss the problem of mounting resistance to TB drugs.