Syphilis is back: The sexually-transmitted disease long associated with 19th-century bohemian life is making an alarming resurgence in Europe.

"Syphilis used to be a very rare disease," said Dr. Marita van de Laar, an expert in sexually transmitted diseases at the European Centre for Disease Prevention and Control. "I'm not sure we can say that anymore."

Most cases of syphilis are in men, and experts point to more risky sex among gay men as the chief cause for the resurgence. But more cases are being seen among heterosexuals, both men and women, as well.

Syphilis was the sexual scourge of the 19th century, and is believed to have killed artists like poet Charles Baudelaire, composer Robert Schumann, and painter Paul Gauguin. But the widespread use of penicillin in the 1950s all but wiped it out in the Western world.

In the last decade, however, syphilis has unexpectedly returned, driven by risky sexual behaviour and outbreaks in major cities across Europe, including London, Amsterdam, Paris and Berlin.

In Britain, syphilis cases have leapt more than tenfold for men and women in the past decade to 3,702 in 2006, according to the Health Protection Agency. Among men in England, the syphilis rate jumped from one per 100,000 in 1997 to nine per 100,000 last year.

In Germany, the rate among men was fewer than two per 100,000 in 1991; by 2003, it was six per 100,000.

In France, there were 428 cases in 2003, almost 16 times the number just three years earlier.

In the Netherlands, cases doubled from 2000 to 2004. In Amsterdam, up to 31 men per 100,000 were infected, while the rate was much lower in other regions.

Similar trends have been seen in the United States. In 2000, syphilis infection rates were so low that the U.S. Centers for Disease Control and Prevention embarked on a plan to eliminate the disease. But about 9,800 cases were reported in 2006.

In Europe, Van de Laar said syphilis' reappearance was so surprising that many doctors initially had trouble diagnosing it. Experts worry that the disease could rebound in the general population if stronger efforts to fight it are not taken soon.

In 2005, British authorities reported that syphilis was spreading across the entire country, and that more heterosexual men and women were being infected.

"These increases may lead to increases in diagnoses of congenital syphilis over the coming years," said Kate Swan, a spokeswoman for the Health Protection Agency.

Pregnant women with syphilis can pass it on to their babies and nearly half of all babies infected with the disease while they are in the womb die shortly before or after birth.

Syphilis is a bacterial disease causing symptoms that include ulcers, sores and rashes. In extreme cases, it can result in dementia or fatally damage the heart, respiratory and central nervous systems. Syphilis is treatable with antibiotics if caught early.