Cases of tuberculosis are set to accelerate worldwide unless action is taken to curb diabetes, a chronic condition that weakens the immune system and triples the risk a person will develop the lung disease, health experts warned on Wednesday.

Tuberculosis (TB), which killed an estimated 1.5 million people last year according to the World Health Organization (WHO), is caused by bacteria that lie dormant in many people.

However, diabetics TB become sick from latent TB infection far more often than other people because their immune systems are compromised -- a fact that could unleash an epidemic of co-infection as diabetes rates soar along with growing obesity.

It is not the first time that the world has been confronted with such co-infection. The HIV/AIDS pandemic, which destroyed the immune systems of millions, lead to a quadrupling of TB rates in many countries in Africa.

Now doctors fear a re-run of that scenario as diabetes takes hold around the world, including in many poorer countries.

The big worry is that six of the top 10 countries projected to have the greatest numbers of diabetics by 2035 -- China, India, Brazil, Indonesia, Pakistan, and Russia -- are classified as high TB burden countries by the WHO.

Anthony Harries of the International Union Against Tuberculosis and Lung Disease told Reuters he was most concerned about India and China, since India has the world's highest TB rate, followed by China, while for diabetes China has the most cases, followed by India.

"We want to raise an alarm that we don’t watch history repeat itself with TB-diabetes,” he said.

Diabetes affected 382 million people in 2013 and will increase to a projected 592 million by 2035, according to the International Diabetes Federation.

Most of the cases will be of Type 2 diabetes, the kind that is linked to obesity and is driven by the adoption of Western diets and more sedentary lifestyles.

"If we don’t act now to head this off, we’re going to experience a co-epidemic of TB-diabetes that will impact millions and sap public health systems of precious resources. The key is to prevent this from happening,” Anil Kapur of the World Diabetes Foundation said.

While diabetes is not as great a co-infection threat as HIV, the virus that causes AIDS raises the risk of TB by thirty fold, there are about 10 times as many cases of diabetes in the world as people living with HIV, so the overall impact is similar.

A joint report from Harries' and Kapur's groups presented at an international lung conference in Barcelona sets out the case for international action against the looming co-epidemic.

The report challenges the conventional approach of tackling independently infectious diseases, like TB, and chronic non-communicable diseases, like TB.

Fighting the threat will need a clear strategy of screening both diabetes patients for TB and TB patients for diabetes, as well as providing treatments for both diseases, the report says. Such "bi-directional" screening is at present patchy.