A spike in syphilis infections in a major Malagasy mining town could predict an HIV epidemic there in future, an official said on Wednesday.

Syphilis, a sexually transmitted disease, is passed from one person to another by direct contact with a sore - and it can facilitate HIV infection, experts say.

“The syphilis prevalence rate in Tolagnaro is 30 percent against a national prevalence rate of 4 percent,” said Fenosoa Ratsimanetrimanana, head of Madagascar’s AIDS commission.

“We should worry about HIV because a higher prevalence rate of syphilis makes (HIV) infection easier.”

The official was referring to a southeast town also known as Fort Dauphin. The enormous Indian Ocean island - where an incipient mining boom is underway - has so far avoided an HIV epidemic that is hitting the African mainland.

Experts say mining communities are especially at risk from HIV, as migrant laborers often indulge in high-risk behavior.

AIDS is hampering operations at a time of booming demand for minerals, mining firms say.

The HIV rate among South African miners is now nearly double that of the general working population, companies say. Worldwide the disease has killed 30 million people.