Rates of the two most common sexually transmitted diseases have increased significantly in Yolo County, according to new numbers from the state Department of Public Health.

The chlamydia rate increased 15 percent from 2011 to 2012 in Yolo County while the gonorrhea rate jumped 90 percent during the same period.

The county’s upward trend mirrors increases statewide, but at a higher rate. In California overall, chlamydia increased by 3 percent and gonorrhea by 23 percent.

Both diseases are bacterial infections that can be easily treated with medication, but when left untreated, can lead to infertility in women.

The rate of chlamydia among women was much higher in Yolo County than for men, with 495 cases among women versus 166 for men, however, research has shown women are more frequently screened for sexually transmitted diseases than are men. Chlamydia is often symptomless, so without that screening, the disease is more likely to be spread.

Gonorrhea is less common, and more men were diagnosed in Yolo County in 2012 than were women — 56 cases among men versus 32 among women.

Yolo County had actually seen a small but steady decline in gonorrhea cases between 2008 and 2011, with the total number of cases dropping from 65 in 2008 to 47 in 2011, before jumping to 88 in 2012.

The chlamydia numbers, on the other hand, had been increasing yearly until they dropped from 578 to 575 between 2010 and 2011, before jumping to 661 in 2012.

According to the Centers for Disease Control, most people who have chlamydia don’t know it since the disease often has no symptoms. It is the most commonly reported sexually transmitted disease in the United States and, while easy to cure, if left untreated, it can reduce women’s ability to have children. Gonorrhea also can be symptomless and, if left untreated, can impair a woman’s fertility.

Both diseases are most common among young adults between the ages of 15 and 24, with the CDC reporting in 2011 that nearly half of the 19 million new cases reported that year coming in that age group. The CDC also reports that Hispanics and African-Americans have higher rates as well.

Public health officials have expressed concern over the increase in both chlamydia and gonorrhea nationwide, because, while both can be treated easily, the same unprotected sex that leads to those infections can lead to other sexually transmitted diseases as well, including HIV.

— Reach Anne Ternus-Bellamy at [email protected] or 530-747-8051. Follow her on Twitter at @ATernusBellamy