Syphilis cases in California jumped 18% from 2010 to 2011, according to new data released by the state Department of Public Health.
The data also show a 5% rise in chlamydia cases and 1.5% increase in gonorrhea cases.
Public health officials said they were concerned about the rise of all three sexually transmitted diseases because they can lead to even more serious health problems, like infertility and an increased risk of HIV.
"The longer people have these infections without being treated the more likely it is they are going to develop a complication that will have both health and financial costs," said Heidi Bauer, chief of the Sexually Transmitted Disease Control Branch for the state public health agency.
Chlamydia affected the highest number of people statewide, with about 164,000 cases reported in 2011. There were 27,000 gonorrhea cases and about 2,500 syphilis cases.