What Are the Most Common STIs and Their Symptoms?

Sexually transmitted infections (STIs) are infections that can spread through sexual contact, including vaginal, anal, or oral sex. Some can also spread through skin-to-skin contact or from a pregnant person to their baby. While many people associate these infections with noticeable symptoms, the reality is that some STIs cause mild symptoms or no symptoms at all. This means you can have an infection without realizing it.

You may also see the term sexually transmitted disease (STD) used when talking about these infections. Although the terms are often used interchangeably, STI is generally broader because it refers to an infection that may or may not have caused disease or symptoms.

In this guide to common STIs and symptoms, we'll look at the most common sexually transmitted infections, the signs and symptoms they may cause, how symptoms can differ between men and women, and when testing or medical care may be appropriate.

What Are STIs and How Are They Spread?

Sexually transmitted infections are caused by bacteria, viruses, or parasites that can be passed between people through sexual or intimate contact. More than 30 pathogens are known to be transmitted through sexual contact, and vaginal, anal, and oral sex are among the main routes of transmission. Some infections can also be transmitted through other types of close skin-to-skin contact or from mother to baby during pregnancy, childbirth, or breastfeeding, depending on the infection.

Understanding how STIs spread is important because transmission does not always require visible symptoms. A person may have an infection and unknowingly pass it to a partner.

What Is the Difference Between an STI and an STD?

The terms STI and STD are often used to describe the same group of infections, and you will commonly see both terms in health information and online searches.

STI stands for sexually transmitted infection, while STD stands for sexually transmitted disease. The term STI is increasingly preferred because a person can carry an infection without developing noticeable symptoms or disease.

For example, someone can have an STI without having pain, discharge, sores, or other obvious signs. This is one reason why searching for STD symptoms or STI symptoms cannot replace appropriate testing when there has been a potential exposure. CDC notes that many people with STDs may not have symptoms and therefore may not know they have an infection.

How Do Sexually Transmitted Infections Spread?

STIs can spread through different types of sexual or intimate contact. The exact route depends on the infection, but common transmission routes include:

• Vaginal sex: Some bacterial, viral, and parasitic infections can spread through vaginal intercourse.
• Anal sex: STIs can be transmitted through anal sexual contact, including infections affecting the rectum.
• Oral sex: Some infections can spread through oral-genital or oral-anal contact.
• Skin-to-skin contact: Certain infections, including herpes and HPV, can spread through contact with infected skin or sores, even when there is no obvious lesion.
• Pregnancy or childbirth: Some infections can pass from a pregnant person to their baby during pregnancy or delivery.

Because different infections have different transmission patterns, having no visible sores or other symptoms does not necessarily mean there is no risk of transmission.

Can You Have an STI Without Symptoms?

Yes. Many STIs can be asymptomatic, meaning a person has the infection without noticeable signs or symptoms. This is one of the most important things to understand when learning about STI signs.

For example, some infections can cause few or no symptoms, while others may produce symptoms that are mild enough to be mistaken for another condition. CDC specifically notes that many people with STDs do not know they have an infection because they do not have symptoms.

The absence of symptoms therefore does not rule out an STI. If there has been a potential exposure or a partner has been diagnosed with an STI, testing and medical advice may be more useful than waiting for symptoms to appear.

The Most Common STIs

There are many different sexually transmitted infections, but some are particularly important because of how commonly they occur or the potential health problems they can cause. The World Health Organization identifies eight pathogens responsible for a large proportion of STI incidence worldwide: chlamydia, gonorrhea, syphilis, trichomoniasis, hepatitis B, herpes simplex virus (HSV), HIV, and human papillomavirus (HPV). Four of these chlamydia, gonorrhea, syphilis, and trichomoniasis are currently considered curable, while the viral infections can be managed in different ways.

The symptoms can vary significantly between infections, and some people may have no noticeable symptoms at all. Here are some of the most common STIs and the signs they may cause.

Chlamydia

Chlamydia is a bacterial STI that can affect the genital tract, rectum, and other sites depending on the type of sexual exposure. One of the challenges with chlamydia is that it frequently causes no obvious symptoms.

When symptoms do occur, they may include:

• Abnormal vaginal or penile discharge
• Burning or pain when urinating
• Pelvic or lower abdominal pain
• Pain during sex in some women
• Testicular pain or swelling in some men

Because chlamydia can be asymptomatic, a person should not rely solely on symptoms to determine whether they have the infection. Untreated chlamydia can also lead to complications, which is why appropriate testing and treatment are important.

Gonorrhea

Gonorrhea is another bacterial STI caused by Neisseria gonorrhoeae. It can affect the genitals, rectum, and throat.

Possible symptoms include:

• Penile or vaginal discharge
• Pain or burning when urinating
• Pelvic or lower abdominal discomfort
• Testicular pain or swelling
• Rectal discomfort, discharge, or bleeding
• Sore throat in some cases

Symptoms can differ depending on the site of infection. Importantly, gonorrhea infections of the throat, rectum, and cervix are often asymptomatic, so the absence of symptoms does not necessarily mean the infection is absent.

Syphilis

Syphilis is a bacterial STI that develops through different stages, and its symptoms can change over time.

The first stage may cause a painless sore, known as a chancre, at the site where the infection entered the body. Because the sore may be painless and can occur in an area that is difficult to see, it may go unnoticed.

Later stages can involve symptoms such as:

• Skin rash
• Swollen lymph nodes
• Fever
• Fatigue
• Sore throat
• Other systemic symptoms

Syphilis can also enter a latent stage in which there are no clinical signs or symptoms. This variation in presentation is another reason why testing can be important when there has been a potential exposure.

Genital Herpes (HSV)

Genital herpes is usually caused by herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2). Many people with genital herpes have no symptoms or only mild symptoms that may be mistaken for another skin condition.

When symptoms occur, they may include:

• Small blisters around the genitals, rectum, or mouth
• Painful sores after blisters break
• Itching or burning
• Pain during urination, particularly when sores are present
• Flu-like symptoms such as fever or body aches during an initial outbreak

Herpes can also be transmitted by a person who does not have a visible sore at the time, which means visible lesions are not required for transmission.

Human Papillomavirus (HPV)

Human papillomavirus (HPV) refers to a large group of viruses, and many HPV infections do not cause noticeable symptoms.

Some HPV types can cause genital warts, while other types are considered high-risk because persistent infection can contribute to certain cancers. The absence of genital warts therefore does not mean a person does not have HPV.

Because HPV infections can be asymptomatic, prevention and appropriate screening recommendations are important parts of sexual health.

Read more: HPV Symptoms, Testing, Treatment, and Prevention

Trichomoniasis

Trichomoniasis is a common STI caused by a parasite called Trichomonas vaginalis. Many infected people do not develop obvious symptoms.

When symptoms occur, they may include:

• Vaginal or penile discharge
• Genital itching or irritation
• Burning during urination
• Discomfort during sex
• Changes in vaginal discharge, including differences in amount or appearance

Symptoms can differ between men and women, and some people may have no symptoms at all. This makes clinical assessment and testing important when infection is suspected.

HIV

HIV (human immunodeficiency virus) can cause symptoms that change depending on the stage of infection.

Some people experience a short-term illness after acute infection that can resemble the flu, with possible symptoms such as:

• Fever
• Fatigue
• Swollen lymph nodes
• Sore throat
• Skin rash

However, HIV can also enter a stage in which a person may have few or no symptoms for an extended period. Because these symptoms are nonspecific, they cannot confirm or rule out HIV; testing is required to determine infection status.

Hepatitis B

Hepatitis B is a viral infection that can be transmitted through sexual contact and can affect the liver. Some people have no symptoms, while others may develop symptoms such as:

• Fatigue
• Loss of appetite
• Nausea or vomiting
• Abdominal discomfort
• Dark urine
• Jaundice, which causes yellowing of the skin or eyes

Because symptoms are not always present, testing may be necessary when hepatitis B exposure is a concern. Hepatitis B is also one of the STIs for which vaccination is available.

What Are the Most Common STI Symptoms?

There is no single set of symptoms that identifies an STI. Different infections can affect different parts of the body, and some infections may cause no noticeable symptoms. When symptoms do occur, however, certain STI symptoms appear more frequently across different infections.

It is also important to remember that these signs are not specific to STIs. Similar symptoms can occur with other infections or health conditions, so symptoms alone cannot establish a diagnosis.

Genital Discharge

An unusual discharge from the vagina, penis, or anus can be a possible sign of an STI. The amount, color, consistency, and odor can vary depending on the infection and the affected area.

However, discharge by itself cannot tell you which infection is responsible. Conditions that are not sexually transmitted can also cause abnormal discharge, so medical evaluation may be needed to determine the cause.

Pain or Burning When Urinating

Pain or a burning sensation while urinating, sometimes called dysuria, can occur with several STIs, including infections affecting the urethra.

It is not, however, an STI-specific symptom. Urinary tract infections and other conditions can cause similar discomfort, so it should not be used as a way to self-diagnose an STI.

Genital Sores, Blisters, or Warts

Sores, blisters, ulcers, or warts around the genitals, anus, or mouth can be STI signs, depending on their cause.

For example, some infections can cause ulcers or sores, while certain types of HPV can produce genital warts. Herpes can cause blisters that develop into painful sores.

Because different conditions can look similar, a healthcare professional may need to examine the affected area and determine whether testing is appropriate.

Itching, Irritation, or Swelling

Itching, irritation, redness, or swelling around the genitals can occur with certain STIs. These symptoms may affect the penis, vulva, vagina, or surrounding skin.

However, they can also result from non-STI causes such as irritation, allergic reactions, or other infections. Persistent or unexplained symptoms should therefore be evaluated rather than automatically attributed to an STI.

Pelvic, Testicular, or Lower Abdominal Pain

Pain in the pelvis, lower abdomen, or testicles can sometimes occur with sexually transmitted infections, particularly when an infection causes inflammation in the reproductive or genital tract.

The severity and location of pain can vary, and these symptoms can have many causes unrelated to sexual infections. Severe, sudden, or worsening pain should receive prompt medical attention.

Rash, Fever, or Flu-Like Symptoms

Some STIs can cause symptoms beyond the genital area. Depending on the infection and stage, a person may experience fever, fatigue, swollen lymph nodes, sore throat, or a rash.

For example, acute HIV infection can produce a nonspecific flu-like illness, while secondary syphilis can cause systemic symptoms and a rash.

These symptoms are particularly difficult to interpret on their own because many common illnesses can cause the same signs. A sexual health history and appropriate testing are more reliable than trying to identify an STI based solely on a rash or flu-like illness.

What Are STI Symptoms in Men and Women?

STI symptoms can vary between people, and the same infection may present differently depending on the affected body site, stage of infection, and individual factors. Some people have noticeable symptoms, while others have none.

For this reason, the presence or absence of a particular symptom should not be used to determine whether someone has an STI.

Common STI Symptoms in Men

When symptoms occur, men may experience signs such as:

1. Penile or urethral discharge
2. Burning or pain during urination
3. Testicular pain or swelling
4. Genital sores, blisters, or lesions
5. Genital itching or irritation
6. Rectal pain, discharge, or bleeding when the rectum is affected

However, not every man with an STI will experience these symptoms. Some infections can remain asymptomatic, and symptoms may also depend on whether the infection affects the genitals, throat, or rectum.

Common STI Symptoms in Women

Women may experience symptoms such as:

• Unusual vaginal discharge
• Burning or pain during urination
• Pelvic or lower abdominal pain
• Pain during sex
• Bleeding between periods or after sex in some circumstances
• Genital sores, blisters, or irritation

As with men, these symptoms are not present in every infection. Some STIs can cause few or no noticeable symptoms, particularly in their early stages.

Why STI Symptoms Can Look Different From Person to Person

There is no universal pattern of STI symptoms in men and women. Two people with the same infection may have different symptoms, while another person may have none at all.

Symptoms can vary based on factors such as:

• The specific infection
• The stage of infection
• The part of the body affected
• Whether the infection is genital, rectal, or oral
• Individual immune response

This variation is why STI signs should be treated as a reason for evaluation, not as a way to confirm a diagnosis. Likewise, having no symptoms does not necessarily mean that an STI is absent. Testing is the most reliable way to determine whether a specific infection is present.

When Should You Get Tested for an STI?

Knowing the possible signs of an STI is useful, but symptoms alone cannot tell you whether you have a specific infection. Testing may be appropriate when you have symptoms, have had a potential exposure, or have risk factors that increase your chance of infection. Importantly, you do not always need to wait for symptoms before considering an STI test. Many infections can be present without noticeable signs.

Should You Get Tested If You Have STI Symptoms?

If you develop symptoms that could be related to an STI, such as unusual genital discharge, sores, burning when urinating, pelvic pain, or other unexplained genital symptoms, it is a good idea to speak with a healthcare professional and ask whether testing is appropriate.

However, symptoms should not be used to diagnose an STI on their own. Similar symptoms can be caused by other infections or medical conditions, and different STIs can produce similar signs. A healthcare professional can consider your symptoms, sexual history, potential exposure, and the appropriate type of testing.

If you have significant or worsening symptoms, seeking medical assessment promptly is especially important rather than waiting for them to resolve on their own.

Should You Get Tested If You Have No Symptoms?

Yes, in some situations. Having no STI symptoms does not necessarily mean that you do not have an infection. Some sexually transmitted infections can remain asymptomatic, which means a person may unknowingly have and transmit an infection.

Whether testing is recommended can depend on factors such as:

• Your age and sexual activity
• The number and type of sexual partners you have
• Whether you have a new sexual partner
• Whether a partner has been diagnosed with an STI
• The type of sexual contact you have had
• Whether condoms or other barrier methods were consistently used
• Previous STI history
• Pregnancy or plans for pregnancy

There is no single testing schedule that applies to everyone. A healthcare professional can help determine which tests are appropriate based on your individual circumstances. CDC recommends discussing sexual history and STI testing with a healthcare provider rather than relying only on symptoms.

The exact recommendations depend on your circumstances, so this table should be viewed as a guide for when to discuss testing, not as a universal testing schedule.

What STI Tests May Be Used?

There is no single test that detects every STI. The type of test used depends on the infection being considered, the symptoms you have, and the part of the body that may have been exposed.

Common testing methods include:

• Urine tests: Often used to detect certain infections affecting the urinary or genital tract.
• Swab tests: A sample may be collected from areas such as the vagina, cervix, throat, urethra, or rectum, depending on the suspected infection and exposure.
• Blood tests: Used for infections that can be detected through blood, including certain viral and bacterial infections.
• Physical examination: A healthcare professional may examine visible sores, lesions, or other physical signs when appropriate.

The most appropriate test is not necessarily determined by symptoms alone. The site and type of sexual exposure can also influence which samples should be collected.

What Should You Do If You Think You Have an STI?

Finding a possible STI symptom can be stressful, but the most useful approach is to avoid guessing the cause and take practical steps toward evaluation and appropriate care.

Avoid Sex Until You Get Medical Advice

If you have symptoms that could indicate an STI or have reason to believe you may have been exposed, consider avoiding sexual contact until you have received appropriate medical advice.

If an STI is diagnosed, follow the recommendations provided by your healthcare professional regarding sexual activity and treatment. Using condoms correctly can reduce the risk of transmitting some STIs, although they do not eliminate the risk of every infection because some infections can spread through skin-to-skin contact.

Don't Self-Diagnose Based on Symptoms

Searching for STI symptoms online can help you understand what may be happening, but it cannot establish a diagnosis.

For example, burning during urination can occur with different infections, while genital sores can have several possible causes. Similarly, the absence of symptoms does not rule out an STI.

Instead of trying to match one symptom to one infection, consider speaking with a healthcare professional who can assess your situation and determine whether testing or treatment is appropriate.

Tell Your Sexual Partner(s) If You Are Diagnosed

If you are diagnosed with an STI, informing current or recent sexual partners can help them seek medical evaluation and, when appropriate, treatment.

Partner notification can also help reduce the possibility of passing the infection back and forth. CDC STI guidance recommends encouraging people diagnosed with STIs to notify their sex partners and have them seek evaluation and treatment.

The conversation can feel uncomfortable, but sharing the information promptly gives partners the opportunity to make informed decisions about their health.

Follow Your Treatment and Follow-Up Plan

If an STI is diagnosed, follow the treatment instructions provided by your healthcare professional and complete the recommended course of treatment.

Depending on the infection, follow-up may also be recommended. This could involve:

• A repeat test
• A follow-up medical appointment
• Additional treatment
• Evaluation or treatment of sexual partners
• Testing for other infections

Do not assume that symptoms disappearing means an infection has necessarily been eliminated. Follow the specific instructions provided by your healthcare professional.

Can STIs Be Treated or Cured?

Whether an STI can be cured depends largely on what causes the infection. Some bacterial and parasitic STIs can generally be cured with appropriate treatment, while viral infections may remain in the body but can often be managed with medical care.

Understanding this difference is important because treatment and cure are not always the same thing.

Which STIs Can Be Cured?

Several common bacterial and parasitic STIs can be cured with appropriate treatment.

These include:

• Chlamydia
• Gonorrhea
• Syphilis
• Trichomoniasis

However, being curable does not mean an infection should be ignored. Treatment should be based on an appropriate diagnosis and medical guidance, and sexual partners may also need evaluation or treatment to reduce the risk of reinfection.

Which STIs Can Be Managed but Not Cured?

Some viral STIs cannot currently be eliminated from the body with an available cure, but medical treatment can help manage the infection and reduce its health impact.

Examples include:

• HIV: Antiretroviral therapy can control HIV and help people live longer, healthier lives.
• Genital herpes: Antiviral medications can help manage outbreaks and reduce transmission risk.
• HPV: In many cases, the immune system clears the infection naturally, while certain HPV-related conditions can be treated.
• Hepatitis B: Some people recover naturally, while chronic infection can require ongoing medical monitoring and treatment.

The management of each infection is different, so a diagnosis should be followed by individualized medical guidance.

Why Early Diagnosis and Treatment Matter

Getting appropriate care can do more than relieve symptoms. Depending on the infection, timely diagnosis and treatment can help reduce the risk of complications and transmission to sexual partners.

For infections that can be cured, appropriate treatment can eliminate the infection. For infections that can be managed rather than cured, early medical care can help people understand their condition and access available treatments.

Testing also provides information that symptoms alone cannot provide. This is particularly important for infections that may remain unnoticed for long periods.

How Can You Reduce Your Risk of STIs?

No single prevention method eliminates the risk of every STI. However, combining safer-sex practices, appropriate testing, communication, and vaccination can significantly improve sexual health.

Use Condoms and Other Barrier Methods

Using condoms correctly and consistently can reduce the risk of many STIs transmitted through genital fluids.

However, condoms do not provide complete protection against infections that can spread through uncovered skin-to-skin contact, such as some cases of HPV or herpes. Using barriers appropriately is therefore one part of a broader STI prevention strategy.

Get Recommended STI Testing

Regular testing can help identify infections that do not cause noticeable symptoms. How often someone should be tested depends on individual risk factors and healthcare recommendations.

If you are sexually active, discussing your sexual history and testing needs with a healthcare professional can help determine which tests may be appropriate.

Talk Openly With Sexual Partners

Communication can play an important role in reducing STI transmission.

Before or during a sexual relationship, partners may want to discuss:

• Recent STI testing
• Previous STI diagnoses
• Condom or barrier use
• New or multiple sexual partners
• Vaccination status where relevant

Open communication does not replace testing, but it can help both partners make informed decisions.

Stay Up to Date on Available Vaccines

Vaccination can help prevent certain infections that can be sexually transmitted.

Two particularly relevant vaccines are:

• HPV vaccine: Helps protect against HPV types associated with genital warts and certain cancers.
• Hepatitis B vaccine: Helps prevent hepatitis B infection.

CDC recommends discussing vaccination against hepatitis A, hepatitis B, and HPV with a healthcare provider when appropriate.

Get STI Care and Testing Support Online With Avee Health

If you are concerned about an STI, experiencing symptoms, or need help determining the next step, speaking with a healthcare professional can help you move from uncertainty to an appropriate care plan.

For people in British Columbia, Avee Health provides virtual healthcare services through BC-licensed physicians. Its medical care service allows patients to discuss new symptoms and ongoing concerns with a physician and receive follow-up care when appropriate.

Get a Lab Requisition for STI Testing

When laboratory testing is appropriate, Avee Health can provide lab requisitions through a virtual consultation. Its Lab Requisition service specifically lists STI testing among the laboratory services available through its physicians.

After an online appointment, the digital requisition can be sent to the patient so they can take it to a laboratory or imaging facility in British Columbia.

Get a Specialist Referral When Needed

Not every STI requires specialist care. However, if a physician determines that a condition requires further evaluation, a specialist referral may be an appropriate next step.

This allows your care to move beyond the initial virtual assessment when more specialized medical expertise is needed.

Access Telehealth From Home in British Columbia

Avee Health makes it possible for eligible patients in British Columbia to connect with physicians remotely rather than visiting a walk-in clinic for every concern. If you're concerned about possible STI symptoms, the first step does not have to be figuring out which infection you have on your own. A virtual consultation through telehealth can help you discuss your concerns and understand what to do next.

Conclusion

STIs can affect anyone sexually active, and one of the most important things to remember is that symptoms do not always tell the whole story. Some infections can cause noticeable signs such as discharge, sores, pain, or irritation, while others may remain unnoticed for a long time.

Understanding common STIs and symptoms can help you recognize when something may need medical attention, but symptoms alone cannot confirm an infection. Testing, particularly after a potential exposure or when recommended based on individual risk factors, is a more reliable way to determine whether an STI is present.

If you develop possible STI symptoms or have concerns about a recent exposure, consider speaking with a healthcare professional rather than self-diagnosing. For people in British Columbia, Avee Health provides virtual medical care and can help patients discuss symptoms, obtain appropriate lab requisitions, and access further care when needed.

For more information, you can visit the AVEE Health blog and read our other articles, which are reviewed by healthcare professionals.