All of the diseases are treatable with antibiotics but can cause significant health problems if not detected sooner.
Data released by the Centers for Disease Control and Prevention (CDC) in its annual report showed there were more cases of chlamydia, gonorrhea, and syphilis reported in the U.S. than ever before, with 2 million new cases in 2016.
In San Diego County, gonorrhea had the most significant increase with 35 percent more cases than the previous year, according to the county's recent report. There were 4,992 cases in 2016, compared to 3,695 cases in 2015.
Men between ages 25 to 29 years old had the highest rate of infection. The rate of gonorrhea was twice as high in men than women.
But the most commonly reported STD in San Diego County and across California is chlamydia. There were 8.5 percent more cases than the prior year in San Diego County, according to the county's report. Women are more likely to suffer from the disease, with a rate 1.6 times higher than men.
It is most common for young women between ages 20 to 24, according to the county. There were 4,867 cases of chlamydia among women in that age group in 2016 and 2,293 cases in men of the same age group. Pregnant women exposed to the disease can suffer stillbirths and deformities in their babies.
San Diego County was one of 14 counties with higher chlamydia rates than the overall state rate, according to the California Sexually Transmitted Disease Annual Report. The disease has reached its highest level statewide since reporting first began in 1990.
Syphilis also increased by 6.7 percent in 2016, according to the county's report. There were 523 cases that year, versus 490 cases in 2015. The majority of the infections affected men in their early to mid-thirties.
Across the state, syphilis increased by 50 percent in women of reproductive age compared with 2015, stated California's report.
California was ranked first out of all the states nationwide for the top number of cases of chlamydia, gonorrhea, syphilis and congenital syphilis confirmed the state's report.
Treatment and prevention programs for STDs have been diminished by budget cuts, health officials said.
For more information about STD testing and clinic services in San Diego County, visit the county's website.