PRAGUE — The Czech News Agency (CTK) has reported an alarming rise in syphilis cases registered by the National Health Institute in July compared to the total for the month last year. A sizeable percentage of the infected were porn performers.

"The source of infection has not yet been identified," chief health inspector Michael Vit told CTK, "but it cannot be ruled out it comes from abroad."

Porn producer Robert Rosenberg informed authorities that the outbreak among the porn community had erupted because of false negative tests submitted by some performers on shoots.

There were 334 new syphilis cases recorded by the Health Institute in July, 23 of which were found in porn performers. The total represented an increase of 59 people over July 2006, with 511 new cases reported for the whole year. The infection was transmitted through heterosexual or homosexual intercourse in 99 percent of the cases.

Gone untreated, syphilis can lead to dementia and eventually death.