Think you can’t catch something from one brief sexual encounter? Think using a condom for vaginal or anal intercourse is plenty of protection? Think getting tested once every few years is plenty often? Think again.

Rates of chlamydia, gonorrhea and syphilis are all higher in San Francisco than they have been over the last five years, according to recently released statistics by the California Department of Public Health. Between 2010 and 2011, chlamydia increased 5 percent, gonorrhea 1.5 percent and infectious syphilis 18 percent.

These particular sexually transmitted infections are especially heinous, and can lead to long-term repercussions and even death. Rates of chlamydia, gonorrhea and syphilis remain highest among gay and bisexual men, and rates of chlamydia and gonorrhea among women under 26 years old.

Here’s why you never want to run into any of these nasties:

• Chlamydia, known as the “silent” infection, is the most frequently reported bacterial sexually transmitted infection in the United States and can cause irreversible damage to the reproductive tract, including infertility. For both men and women, it can be tough to diagnose based on symptoms, although men could experience penile discharge and pain or swelling in the testicles.

• Gonorrhea is a bacterium that easily grows in moist, warm areas of the reproductive tract and can also pop up in the mouth, eyes, throat and anus. If women exhibit any symptoms, they can easily be mistaken for a bladder or vaginal infection. Most men don’t experience symptoms, but some will have white, yellow or green discharge leaking from the penis one to 14 days after contracting the disease. If left untreated, gonorrhea can lead to life-threatening complications.

• Syphilis, which can be contracted through a sore that the infected party doesn’t even know exists, can go unnoticed for years while still doing damage to the body. The second stage of the infection comes with a repulsive rash on the palms of the hands or bottom of the feet. If not treated, it can lead to organ damage, blindness, dementia and a host of other miserable symptoms that will inevitably lead to an even more miserable end.

Use barrier methods: condoms (male or female), dental dams, finger cots and anything else as a barrier between your bodily fluids and your partner’s. This should be a given during all sexual encounters. Don’t take someone’s word on test results, even if you see them. They could have contracted something since the test or have something that just hasn’t shown up yet.

Even if you practice safe sex, you must always know your own status. No excuses. Regular testing is absolutely essential. How often you get tested, however, depends on you.

“It is recommended that an individual be tested once every three to six months, depending on how sexually active you are and how frequent your barrier use is,” peer sexual health educator Brianna Williams said. “The time frame of three to six months is selected because STIs have different window periods, meaning if you’re exposed to an STI, it won’t necessarily show up before a certain time when a test can recognize it.”

The cases of all three of these infections have also increased throughout California, with no clear reason, according to Dr. Susan Philip, director of STD prevention and control services at the San Francisco Department of Public Health, who spoke to Examiner.com.

To add to this infection-ridden fun, people with sexually transmitted diseases are two to five times more likely to get infected with HIV than those who are uninfected, according to the Centers for Disease Control and Prevention. Anyone who is sexually active can contract an STI — there is no shortage of reasons to get tested.

Testing involves either a urine or blood test. These tests take a few minutes at most, and the blood test is only slightly uncomfortable, Williams said, and “worth it in the end.”

Don’t worry. There’s no lack of places to go to get a clean bill of health.

“The health center is a great convenient place for students of SFSU to go to, but there are of course other sites around the city, especially if you’d like anonymous testing. There’s the API Wellness Center, Magnet and even Planned Parenthood. Or, of course, you can visit your primary health care provider,” Williams said.

But she emphasizes that where you go isn’t what truly matters.

“The where you get tested isn’t as important so much as the act of getting tested at some point.”