Antiretroviral (ARV) treatment used to treat HIV may cause leprosy in a few people. Though only a dozen cases have been documented till now, international experts fear it may trigger a leprosy epidemic in countries such as India, with many cases of leprosy and a steadily growing number of people on ARVs.

Public health experts in India and the Asia-Pacific region, however, believe that the threat of ARVs uncovering hidden leprosy infection in stray cases is not cause for concern. "ARVs have been in use globally for almost two decades and I have been using them in India since 1990. Though almost 50 per cent people with HIV have a TB infection, I have not come across even one case of leprosy in people on ARVs in India or the Asia Pacific," says Dr Chinkholal Thangsing, Asia Pacific Bureau Chief, AIDS Healthcare Foundation.

In fact, while people with HIV/AIDS and those taking ARVs have risen sharply in India over the past two years, leprosy cases have gone down. There are 5.7 million people living with HIV in India, a little over 1 per cent of who are on medication to treat AIDS. Experts say that with so many people being treated for AIDS, some cases of leprosy would have definitely been reported.

Ironically, the opposite has happened - leprosy prevalence rate has fallen from 0.95 in December 2005 to 0.88 at the end of August 2006. The total number of cases under treatment has dropped from 106,666 to 99,723 in the same period, bringing down leprosy cases under 1 lakh for the first time in the country's history.

Globally, only a dozen cases of leprosy triggered by ARVs have been documented since the initial report in Clinical Infectious Diseases (volume 36, 2003) that linked the presentation of leprosy in a person two months after he started taking AIDS medication. So new is the problem for Indian scientists that no work is yet being done on the subject in India. "This is the first time I have heard of the association. It seems like a side-effect in individuals with an immune dysfunction and not a public health issue," says a deputy director of molecular virology, NARI.

Sujatha Rao, director of the National AIDS Control Organisation, too, dismisses the association between HIV and leprosy. "Currently, 50,000 people are getting free antiretroviral medication under the government programme and I have not come across any case of ARVs causing leprosy. It has never even featured in the several scientific sessions I have attended on AIDS," says Rao, who heads the department responsible for distributing free ARVs to 44,000 people. Another 6,000 are distributed through health initiatives in the public sector, such as Railways and other public sector units.

Fixed-dose combinations of the drugs Zidovudine, Lamivudine and Nevirapine are given free under the government programme.

Experts say the few cases of leprosy in HIV positive people should not put people off ARVs. "Leprosy can be cured using antibiotics for six months under the government programme, unlike HIV, which needs a lifetime of treatment. Stray side-effects of the immune system should not send out the message, 'don't get treatment for HIV'," says Thangsing.

The good news is that public health experts had wrongly predicted that leprosy would prove fatal to HIV-infected because it is caused by a bacterium from the same family as the ones that cause TB and mycobacterium avium complex - the leading killers of people with AIDS.