The Global Fund to fight AIDS, TB and Malaria, which has helped prevent 4.1 million deaths from TB, no longer has the resources to expand its work against the infectious disease, the International HIV/AIDS Alliance, the Stop AIDS Campaign and anti-poverty group Results UK said in a joint statement.

"We are facing some huge challenges, particularly in that over 80 percent of the external funding that is going into tuberculosis control is going through the Global Fund' and the Global Fund is facing a funding crisis," Aaron Oxley, executive director of Results UK, told reporters in a telephone briefing.

"The problem is that infectious diseases don't slow down when the money slows down - they keep infecting and that's building up a bigger problem for us to deal with in the future."

TB is a worldwide pandemic that kills around 1.5 million people a year and is caused by the bacterium Mycobacterium tuberculosis.

The infection destroys patients' lung tissue, causing them to cough up the bacteria, which then spread through the air and can be inhaled by others. In 2010, 8.8 million people had TB, according to the World Health Organization (WHO).

The three NGOs who issued their statement ahead of World TB Day on March 24, called on governments to scale up funding of TB, HIV and malaria programs at a G20 meeting in Mexico in June in an effort to replenish the Global Fund with $2 billion.

The public-private Global Fund to Fight AIDS, Tuberculosis and Malaria, the world's largest financial backer of the fight against the three infectious diseases, said in November it had been forced to cancel new grants and would make no new funding available until 2014.

Oxley said the effect of that decision was to create a funding shortfall of $1.7 billion for work on treating TB over the next five years.

Since it was founded in 2002, the Global Fund says it has helped detect and treat 8.6 million cases of TB.

The international medical charity Medecins Sans Frontieres said the lack of Global Fund money put the fight against TB at risk and would leave countries "unable to aggressively tackle their TB epidemics."

MSF also warned in its World TB Day statement that the spread of multi-drug resistant TB (MDR-TB) is much greater than previously estimated.

"Wherever we look for drug resistant TB we are finding it in alarming numbers," said MSF president Unni Karunakara. "And with 95 percent of TB patients worldwide lacking access to proper diagnosis, efforts to scale up detection of MDR-TB are being severely undermined by a retreat in donor funding — precisely when increased funding is needed most."

Over the next two years, the Stop TB Partnership estimates that globally 244,000 people will go untreated for TB, 40 percent of them living in Mozambique and Tanzania. In Zambia, almost 11,000 TB patients and almost 132,000 HIV positive people are at risk due to funding shortfalls.

Because the human immunodeficiency virus (HIV) that causes AIDS weakens the immune system, people with it are much more likely to be infected with TB. Around 34 million people around the world have HIV, and the majority of them live in Africa.

"We have done ... well in terms of providing treatment for people with TB because of the funds ... from the Global Fund," said Michael Gwaba, a Zambian TB-HIV patient who works for the Community Initiative for TB, AIDS and Malaria (CITAM+). "Our present worry is that if the Global Fund is not funded, that is going to affect all the work we've done within the country."

(Additional reporting by Kate Kelland, editing by Tim Pearce)

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