The authors say their find confirms that a passage in the Atharva Veda, a set of Sanskrit hymns written around 1550 B.C., indeed refers to leprosy, a reading that had been doubted because until now the oldest accepted written accounts of the disease were from the sixth century B.C.

Image Possibly the oldest skeletal evidence of leprosy includes tooth loss and root exposure on this 4,000-year-old mandible.

The bacterium that causes leprosy seemed to have spread worldwide from a single clone, biologists reported three years ago. But for lack of sufficient samples, they could not tell whether the bacterium was disseminated when modern humans first left Africa about 50,000 years ago, or spread from India in more recent times.

Other biologists have contended that because the bacterium is not very transmissible, requiring prolonged intimate contact between people, it would not have started to spread until around the third millennium B.C., when people started living in dense populations in cities and long-distance trade sprang up.

Helen D. Donoghue, an infectious disease specialist at University College London, said the new finding was fascinating and fit in with the theory that Alexander’s army had brought leprosy back from its campaigns in India.

This was the right period for leprosy to have spread from India to Europe, Samuel Mark, an anthropologist at Texas A&M, argued in an article in 2002. But he doubted that Alexander’s troops were the mode of transmission. More likely, in his view, is the possibility that leprosy arrived with women imported as slaves by ship from India to Egypt.