DENVER — The number of Denver residents with the three most common sexually transmitted diseases increased for the fourth straight year, Denver Public Health officials said on Tuesday.

Experts believe that the increased rate of chlamydia, gonorrhea and syphilis are partly due to fewer men wearing condoms.

Chlamydia is the most common sexually transmitted disease in the city with diagnoses increasing by 24 percent over the last four years, officials said. It affects an estimated 7,317 residents, or more than one in 100 people in Denver.

“Chlamydia is often called the silent epidemic, because 80 percent of the time, women don’t know they have it,” said Dr. Karen Wendel, director of HIV/STD prevention at Denver Public Health. “Then, years later, because of a previous chlamydia infection, women can suffer from infertility or life-threatening complications of pregnancy.”

Gonorrhea infections grew the most over the past four years with an increase of 150 percent in 2018 compared to four years earlier.

Syphilis is also up 75 percent over the past four years to 405 new cases in 2018.

“The best way to prevent STDs is to use a condom every time and limit your number of partners,” said Wendel.  “What’s more: all sexually active young men and women should ask their provider about being tested for STDs at least once a year.”

Officials said that most health insurance plans cover STD testing for sexually active women or for men who are at high risk.  However, STD testing is not always routine or an “automatic” part of a health care visit so they encourage young people to ask their provider for a test.