Sexually transmitted diseases are infections passed mainly through sexual contact. They fall into four broad groups: bacterial, viral, parasitic, and fungal. There are more than 30 known bacteria, viruses, and parasites that spread this way. The most common ones in the United States are chlamydia, gonorrhea, syphilis, trichomoniasis, genital herpes, human papillomavirus (HPV), and HIV.
What Are All The STDs Bacterial Viral More?
The word “STD” means a disease with symptoms. “STI” means an infection, which may cause no symptoms at all. Health agencies increasingly use STI because many people carry these infections without ever feeling sick.
Grouping them by cause matters. It tells you whether a cure exists, how the infection spreads, and how to avoid it.
- Bacterial — chlamydia, gonorrhea, syphilis, and chancroid. These are caused by bacteria and can usually be cured with antibiotics.
- Viral — HIV, herpes, HPV, hepatitis B, and hepatitis C. These cannot be cured in most cases, but antiviral medicines can control them.
- Parasitic — trichomoniasis and pubic lice. These are caused by tiny organisms and are treatable.
- Fungal — yeast infections and some forms of tinea. These are often not sexually transmitted at all, though they can spread through close contact.
One clarification worth knowing: not every infection on a list of STDs spreads only through sex. Zika, for example, can pass through sexual contact but mainly spreads through mosquito bites. The label describes how an infection can spread, not how it always does.
Which STDs Are Bacterial?
Bacterial STDs are the ones with a clear cure. A course of the right antibiotic clears the infection, though it does not protect you from getting it again.
Chlamydia is the most commonly reported bacterial STI in the US. It often causes no symptoms. When it does, they may include unusual discharge or a burning feeling when urinating. Left untreated, it can lead to pelvic inflammatory disease in women, which can damage the fallopian tubes and cause infertility.
Gonorrhea behaves similarly. It can infect the genitals, rectum, and throat. Some strains have developed resistance to several classes of antibiotics, which is why public health agencies track it closely and why treatment follows current guidelines rather than older ones.
Syphilis moves in stages. A painless sore appears first, then a rash, then a long quiet period. Without treatment, it can eventually damage the heart, brain, and nerves. It can also pass from a pregnant woman to her baby, which is why testing in pregnancy is standard.
Chancroid is rare in the US but still occurs in some parts of the world. It causes painful sores.
Which STDs Are Viral?
Viral STDs are managed, not cured, with a few exceptions. Hepatitis C can now be cured with antiviral medicines in most people who complete treatment. That is a genuine change from a few decades ago.
HIV attacks the immune system. Without treatment it progresses to AIDS. With modern antiretroviral therapy, most people with HIV live a normal lifespan and cannot pass the virus to partners when the virus is suppressed to undetectable levels. This is one of the best-established facts in HIV medicine.
Genital herpes comes from herpes simplex virus, usually type 2 but sometimes type 1. It causes recurring sores or no symptoms at all. Antiviral medicine shortens outbreaks and reduces the chance of passing it on, but does not remove the virus from the body.
HPV is the most common STI overall. Most sexually active adults get it at some point. The immune system clears most infections on its own within a couple of years. A small number of strains cause genital warts, and a small number cause cancers of the cervix, throat, anus, and other sites. Vaccines are available and are recommended in early adolescence, though they are approved for certain older age groups as well.
Hepatitis B spreads through sex as well as blood. Many people clear it; others carry it long-term. A vaccine exists and is part of routine childhood immunization in the US.
What About Parasitic and Fungal Infections?
Trichomoniasis is caused by a parasite. It is very common and often causes no symptoms. When it does, it can produce discharge, itching, or discomfort during urination. It is treated with prescription medicine, and partners usually need treatment too.
Pubic lice are tiny insects that live in coarse body hair. They spread through close contact, including sex. They are treatable with creams and shampoos.
Scabies is a mite that burrows into the skin and causes intense itching. It spreads through prolonged skin-to-skin contact, which can include sex but is not limited to it.
Fungal infections like yeast are a common source of confusion. Candida yeast lives on the skin and in the body normally. A yeast infection is usually not sexually transmitted, though sexual activity can sometimes trigger one. Treating a partner is generally not recommended, because it does not prevent recurrence.
How Do the Main STDs Compare?
The table below shows the practical differences. It is not a substitute for testing or medical advice.
| Infection | Type | Curable | Common Symptoms |
|---|---|---|---|
| Chlamydia | Bacterial | Yes | Often none; discharge, burning |
| Gonorrhea | Bacterial | Yes | Often none; discharge, burning |
| Syphilis | Bacterial | Yes | Sores, rash, later organ damage |
| HIV | Viral | No, but controllable | Early flu-like illness, then often none for years |
| Herpes | Viral | No, but controllable | Sores, tingling, sometimes none |
| HPV | Viral | No, but usually clears on its own | Often none; warts in some strains |
| Trichomoniasis | Parasitic | Yes | Often none; discharge, itching |
Notice how many entries say “often none.” That is the single most important pattern here. Most people with an STI do not know they have one.
How Common Are STDs?
Very common. Federal health agencies estimate that tens of millions of new infections occur in the US each year, and that a large share of sexually active adults will have at least one at some point.
Rates are not evenly spread. Young people aged 15 to 24 account for a disproportionate share of new cases, largely because of higher rates of new partnerships and lower testing rates. Some infections, including syphilis and gonorrhea, have risen in recent years after a long decline.
Exact numbers change year to year. If you want current figures, the CDC publishes an annual surveillance report.
How Are STDs Transmitted?
Transmission happens through contact with infected body fluids or skin during sex. That includes vaginal, anal, and oral sex. Some infections, like herpes and HPV, spread through skin-to-skin contact, which means a condom reduces but does not fully eliminate the risk.
Other routes exist:
- Sharing needles can pass HIV, hepatitis B, and hepatitis C.
- Pregnancy, childbirth, and breastfeeding can pass some infections to a baby.
- Blood transfusions once spread HIV and hepatitis; screening has made this rare in the US.
You cannot get an STI from a toilet seat, a swimming pool, or sharing a fork. That myth has persisted for decades and is not supported by how these organisms survive outside the body.
When Should You Get Tested?
Testing is the only way to know. Symptoms are an unreliable guide, because many infections cause none.
General guidance from public health agencies suggests:
- All adults and adolescents should be tested for HIV at least once.
- Sexually active women under 25 should be tested for chlamydia and gonorrhea yearly.
- Pregnant women should be tested for syphilis, HIV, hepatitis B, and usually chlamydia.
- Anyone with a new partner, multiple partners, or symptoms should talk to a clinician about what to test for.
Specific testing intervals vary by risk factors, age, and anatomy. A clinician can tell you what applies to you. No single panel covers everything, and some infections, like herpes, are not routinely screened for in people without symptoms.
Can STDs Be Prevented?
No method removes risk entirely, but several reduce it substantially.
Condoms lower the risk of most STIs when used correctly and consistently. They are more effective against infections spread by fluids than against those spread by skin contact.
Vaccines exist for HPV and hepatitis B. Both are well studied and widely recommended.
Testing and treatment of both partners reduces spread. So does being honest with partners about status.
PrEP is a medicine that prevents HIV in people at higher risk. It does not protect against other STIs.
There is no vaccine for chlamydia, gonorrhea, syphilis, herpes, or trichomoniasis. Anyone claiming otherwise is not describing an approved product.
Frequently Asked Questions
What is the difference between an STD and an STI?
An STI is an infection, which may cause no symptoms. An STD is the disease state that can develop from an untreated infection.
Can you have an STD with no symptoms?
Yes. Many of the most common infections, including chlamydia, gonorrhea, HPV, and herpes, often cause no noticeable symptoms.
Which STDs are curable?
Bacterial infections like chlamydia, gonorrhea, and syphilis can be cured with antibiotics, and trichomoniasis can be cured with prescription medicine. Viral infections like HIV and herpes cannot be cured but can be controlled with treatment.
How often should you get tested for STDs?
It depends on your age, anatomy, and risk factors. General guidance suggests at least one HIV test for all adults, and yearly chlamydia and gonorrhea testing for sexually active women under 25.
