A new report warns of tuberculosis-diabetes epidemic as the two diseases intertwine in many countries, driven in part by a rise in unhealthy lifestyles.
Having diabetes triples a person's risk of contracting TB, which killed about 1.5 million people last year, said the report compiled by the International Union Against Tuberculosis and Lung Disease and the World Diabetes Foundation.
A growing link has been observed between diabetes -- a disease of diet, lifestyle and genes -- and TB, a respiratory disease spread by bacteria, it said.
The physiological mechanisms are not fully understood, though.
"Diabetes is fuelling the spread of TB," said the report released for the 45th World Conference on Lung Health in Barcelona.
"This is largely because diabetes rates are skyrocketing around the world, and having diabetes increases the risk that a person will become sick with TB."
It warned: "Successfully addressing TB-diabetes therefore requires a coordinated response to both diseases at all levels of the health system."
According to the report, it was estimated that there were more people in the world living with a combination of TB and diabetes than there were people living with TB and HIV -- a well-known duo that has claimed millions of lives.
The AIDS-causing virus lowers the body's immune defences, which has allowed TB to spread like wildfire.
- Leading causes of death -
Individually, TB and diabetes are already among the world's leading causes of death and disability.
According to the World Health Organization (WHO), about 347 million people have diabetes worldwide, and over three million die in a year.
Usually thought of as a rich country disease, 80 percent of diabetes-related deaths now occur in low- and middle-income countries.
Ninety percent of sufferers have Type 2 diabetes, which is largely caused by being overweight and not exercising enough, says the WHO.
TB, for its part, is the second-most deadly infectious disease after AIDS.
About nine million people fell ill with TB last year and 1.5 million died, according to the WHO. Ninety-five percent of deaths occur in low- and middle-income countries.
It causes one in four deaths of people infected with HIV.
The new report pointed to a study in the Indian state of Tamil Nadu which found that 25 percent of TB patients also had diabetes.
Twelve percent of nearly 9,000 TB patients screened in China had diabetes, as did nearly 30 percent of 1,200 TB patients screened in southern Mexico, it said.
By 2030, India, China, Indonesia, Pakistan and Brazil together are projected to have half of the world's people living with diabetes, and are also high-TB burden countries.
"This... report is a call to action to address this threat before it takes a larger toll in death and disability as well as economic impact -- and before we see the gains made against TB in the past decade rolled back by diabetes," said the report.
By 2030, the direct costs of diabetes are projected to increase to $486 billion (381 billion euros) globally -- 72 percent of which will be in middle-income countries, said the report.