By: Kasia Galazka

You may think you know everything you need to know about STDs: Syphilis was a threat, like, 200 years ago, HPV is a woman thing, and HIV is really scary—but would never happen to you. Plus, you wear condoms like a good, responsible guy, so you have nothing to worry about, right?

Not exactly. Most people are under the impression that only societal “outcasts” get STDs, says Jill Grimes, M.D. and author of Seductive Delusions: How Everyday People Catch STDs. “Let me tell you, that is not the population I treat with STDs. My patients are doctors, lawyers, accountants, teachers, models, students, and athletes.”

Here’s another fact: Condoms don’t fully protect you against STDs that are spread from skin-to-skin contact, says Grimes. That makes you susceptible to herpes, syphilis, HPV, and pubic lice—not to mention the 11% annual fail rate of condoms.

So what can you do?

First, get tested. Make an appointment with your regular physician or contact a Planned Parenthood to get screened for cheap. While getting your penis swabbed or being jabbed with a needle might be uncomfortable, it sure beats a bad case of the clap—or an angry partner whom you unknowingly infected.

Second, refresh your facts to protect yourself: We dug up the most up-to-date data on the six most prevalent STDs and how to prevent them—without swearing off sex.

Chlamydia

Here’s the good news about chlamydia (never thought you’d hear us say that, right?): It’s a curable bacterial infection that rarely causes complications in men if untreated. But here’s the bad news: It’s spreading like wildfire. Chlamydia is the most commonly reported infectious disease in the country, and the Center for Disease Control and Prevention (CDC) estimates that there are about 2.8 million new annual cases—but only 1.1 million were reported in 2007. That means about half don’t know they’re infected and don’t receive proper treatment.

Prevention:
Use a condom. Chlamydia is spread through bodily secretions, and it’s largely asymptomatic, meaning people who have it show no symptoms.
Have sex with one person who you know is uninfected.
Annual screening for men and women with new or multiple sex partners.

Symptoms:
A burning sensation when urinating
An abnormal release of fluid that is not urine or semen (called penile discharge)
Untreated cases can lead to complications that can cause pain, fever, and more rarely, sterility.

Treatment:
Oral antibiotics

Things to remember:
You can re-infect your partner, even if she’s received treatment.
If you’re being treated, make sure your partner is, too. Women can suffer long-term complications like infertility, says Grimes.
If you’re exposed to HIV, it’s more likely to be transmitted to you if you have chlamydia.

Gonorrhea

Probably the most gnarly-sounding STD, gonorrhea—also known as “the clap”—is actually easily cured. Like Chlamydia, it’s caused by bacteria, so a simple course of antibiotics will zap the clap right out of your system. According to the CDC, it’s the second most reported infectious disease, with nearly 356,000 infections in 2007, but it’s estimated that about twice as many new cases actually occur but are undiagnosed and unreported.

Prevention:
Use a condom. Gonorrhea is also primarily transmitted through semen and vaginal secretions—and it can be asymptomatic, meaning you don’t show any symptoms.
Have sex with one person who you know is uninfected.

Symptoms:
Usually develop within 10 days
Discharge from the urethra (opening where urine comes out)
Redness around the urethra
Frequent urination
Pain or discomfort during urination

Treatment:
Antibiotics
Gonorrhea has shown resistance to certain drugs, so as of 2007, treatments are limited to one type of antibiotic, the CDC reports.

Things to remember:
Women can suffer severe complications if the disease goes untreated. Every year chlamydia and gonorrhea cause about 100,000 infertility cases, says Grimes.
Men can develop epididymitis, an inflammation around the testicles that can cause infertility.
If you’re exposed to HIV, it’s more likely to be transmitted to you if you have gonorrhea.

Syphilis

Syphilis may have peaked in 19th century with all that bonking on the Oregon Trail, but there’s been a re-emergence of the disease in the 2000s, says Scott Bryan, a spokesperson for the CDC. Syphilis is caused by bacteria and can cause sores on the skin. Translation: It’s not pleasant. The upside is that it’s easily curable in its primary and secondary stages.

Prevention:
Since syphilis is spread from sores through tiny breaks in the uninfected partner’s skin, a condom is your best bet—but it won’t fully protect against the disease.
Have sex with one person who you know is uninfected.

Symptoms:
Primary syphilis: An ulcer, or sore, at the infection site
Secondary syphilis: A rash, which may look like “copper penny” spots or fine red dots on palms or soles of feet; a skin rash on arms, legs, and trunk that can take many forms like small blotches, indented circles, small pus-filled blisters, or thick gray and pink patches; white patches inside the mouth and other mucous membranes
Other Symptoms: Enlarged lymph nodes, fever, headaches, muscle aches, sore throat, poor appetite, weight loss, feeling extremely tired
Latent stage: No symptoms, but one-third progress to the tertiary stage
Tertiary syphilis: Severe organ damage: destructive tumors (gummas), chest pain or breathing difficulties related to heart damage, symptoms related to joint damage, symptoms of damage to nerves and brain

Treatment:
Penicillin

Things to remember:
Syphilis is highly infectious.
If you have syphilis, make sure your partner is treated, too.
The disease makes the HIV virus more transmittable.

Human Papillomavirus (HPV)

You may know this better as genital warts—and also for those commercials featuring excessively upbeat teenage girls jumping rope. There are more than 100 types of HPV and about a third of those can infect your genital area, the CDC reports. Long-term health risks like HPV-related cancer are rare in men, but women with HPV have higher odds of developing cervical cancer. So if you have symptoms, be a good guy and have it looked at—especially since there is no general test for men yet. The bad news is that there is no way of testing its prevalence among men, says Bryan.

Prevention:
Condoms lower the risk of infection, though they won’t fully protect you since HPV is passed by skin-to-skin contact.
Women between the ages of 9 and 26 can receive a vaccine that protects them against HPV, and the shot may be approved for men as soon as this year.
Have sex with one person who you know is uninfected.

Symptoms:
Genital warts, or pink, painless growths with a rough, cauliflower-like surface that can affect the tip of the penis, opening of the urethra, or skin around the anus

Treatment:

Removing or freezing warts surgically
Topical medications

Things to remember:
HPV doesn’t always cause warts. Some people never have symptoms and don’t know that they have it.
With a strong immune system, an infection may go away on its own.
Since men can be carriers, get tested and always inform your partner if you have it.

Genital Herpes

While it’s not one of the three most common STDs, genital herpes may be one of the most dreaded because there is no cure. If you contract the herp, you’ve got it for life. There are two strains of the virus: herpes simplex virus type 1 (HSV-1), which causes cold sores, and herpes simplex virus type 2 (HSV-2), which is responsible for genital herpes. At least 50 million people in the country have genital herpes.

Prevention:
A condom lowers the risk of contraction, but HSV is spread from skin-to-skin contact.
Have sex with one person who you know is uninfected.

Symptoms:
Occur usually within 2 weeks after contact
Itching, burning, soreness, and small blisters in the genital area
Small ulcers (skin sores) when blisters break
Local pain if urine touches ulcers
Enlarged or painful lymph nodes (swollen glands) in the groin
Headache, fever, and generally sick feeling

Treatment:
No treatment
Antiviral medications to control duration and prevent outbreaks

Things to remember:
The first outbreak is usually the worst.
A person does not have to have symptoms to spread genital herpes.
Despite popular belief, HSV-1 can cause HSV-2 through oral sex.
The disease makes the HIV virus more transmittable.

Human Immunodeficiency Virus (HIV)

There’s no joking around about this one: The HIV/AIDS epidemic has killed more than 25 million people worldwide, and it’s not a thing of the past. About 75% of people living with HIV are men and the most recent CDC data estimates that 56,000 new infections occurred in 2006. HIV weakens your body’s immune system and destroys a certain type of white blood cells (CD4 lymphocytes) that guard your body from bacteria.

Prevention:
Use a condom for both intercourse and oral sex. HIV is transmitted primarily through bodily secretions.
If you use intravenous drugs, never share needles.
If you are a health care worker, strictly follow universal precautions (the established infection-control procedures to avoid contact with bodily fluids).
Have sex with one person who you know is uninfected.

Symptoms:
Early stages have no symptoms or cause flu-like illness
Some early infections may progress to meningitis or severe flu-like symptoms that require hospitalization
As CD4 cell levels drop below normal, you may develop swollen lymph nodes, skin problems, or ulcers around the mouth
As more cells die, skin problems and mouth problems develop more often, like herpes or shingles
As CD4 cells decrease, the person develops AIDS

Treatment:
Highly active antiretroviral therapy (HAART) to suppress virus, increase CD4 count, and strengthen immune system

Things to remember:
Always inform your past partners if you’ve been diagnosed with HIV.
Advances in HIV treatment have kept deaths at a stable level, but it remains an epidemic.
If you think you’ve been exposed to HIV, contact your doctor immediately. The risk of you getting HIV/AIDS can be decreased with post-exposure prophylaxis, which is a combination of HAART.