AS A world-renowned photo-journalist who has covered war zones across the globe, James Nachtwey is no stranger to pain and suffering. But a five-month tour of some of the world's impoverished nations this year almost broke his heart.

Nachtwey, 60, has just returned from a trip through India, Thailand, Cambodia, South Africa, Lesotho, Swaziland and Siberia, capturing the haunting faces of those dying from the lung disease tuberculosis.

About 15 million people across the world have tuberculosis, most in developing countries, and about 1.7 million die from it each year. The World Health Organisation fears those numbers will soon soar as the disease mutates and becomes more resistant to front-line drugs.

One new strain, XDR-TB, or extensive drug resistant TB, is already cutting a swathe across developing countries and leaving doctors helpless.

XDR-TB, first documented in 2006, is most common in Asia and the Eastern bloc. The disease mutates when drugs are not prescribed properly, are of poor quality or in erratic supply.

"The normal strain of tuberculosis is preventable, treatable and curable but these people have no voice. They are nothing more than statistics to most. I wanted to put a human face on this issue and bring their suffering to a wider audience," Nachtwey says.

"If we can get a greater public awareness of what is going on, we can facilitate funding, research and care."

Nachtwey's photo essay will be launched today with images projected onto buildings across London and New York and on huge screens in 50 cities, including Milan, Los Angeles, Seoul Hong Kong and Melbourne.

"I'm hoping it makes world leaders act," Nachtwey says.