One of the ways health officials aim to fight it is through education.
"Letting them know that we’re here to help and educate," said Hemal Parikh, the San Joaquin County HIV/STD program coordinator.
Parikh says he’s been presenting this information to doctors over the last 18 months. In a county that now ranks second highest in the state for the number of syphilis cases, the latest data shows there was an almost 44 percent increase from 2016 to 2017.
"We’re just trying to inform the public as much as possible that this is a public health concern in the county," said Dr. Kismet Baldwin, a health officer with San Joaquin County Health Services.
Baldwin says left undetected the infection could lead to serious health issues.
"If you’re not treated you move onto the secondary stage and in the secondary stage you could have multiple sores like that but it could be in the mouth," Baldwin told FOX40.
She adds a big concern is among pregnant women.
"Women in our county of childbearing age, it can be passed on to their babies and that is a very big public health issue," she said.
Baldwin says congenital syphilis led to three stillbirths last year.
"Premature birth, you could have miscarriages, you could also have a stillbirth," Baldwin said.
She advises people who are sexually active to get tested.
"Can pass it on to somebody else and that person can pass it on to somebody else if it’s not treated," she said.
Dr. Baldwin says homelessness, lack of access and changes in sexual behavior could all contribute to the growing number. But specific influences are hard to nail down.
"It's probably not going to end up being one thing, one specific thing," Baldwin said. "I think there’s a lot of factors playing into it."
While the information may seem ominous, Baldwin reminds the public sexually that transmitted infections are treatable and preventable.
Most of the symptoms cannot be reversed, so Baldwin highly encourages the public to get tested.
The county also plans to test individuals within the homeless population starting next month. The STD program coordinator says about 20 percent of their syphilis cases are homeless people.