Sexually transmitted infections, or STIs, are incredibly common—more than a million people around the world get one every day. Yet despite how widespread they are, STIs are often misunderstood and weighed down by stigma. That stigma can prevent people from getting tested, talking to their partners, or accessing care. It can also make the topic feel intimidating or off-limits, when in reality, understanding STIs is a key part of taking care of ourselves and others.
Most STIs are either curable or manageable. Bacterial infections like chlamydia, gonorrhea, and syphilis can typically be cleared up with antibiotics. Viral infections like herpes or HPV might not go away completely, but there are effective treatments to help manage symptoms and reduce the risk of transmission. The problem isn’t that these infections exist—it’s that shame and misinformation often keep people from dealing with them openly.
This guide is here to offer a clear, judgment-free starting point. If you’ve ever wondered what STIs are, how they spread, or why they matter, you’re in the right place. Knowing the basics isn’t just about personal health—it’s about empowerment, communication, and reducing the silence that too often surrounds sexual health.
What Does “STI” Actually Mean?
Understanding what STIs are starts with the words themselves. For many years, the term “STD”—sexually transmitted disease—was commonly used. But today, “STI,” which stands for sexually transmitted infection, is the more accurate and widely accepted term.
STI vs. STD: Why “Infection” Is Now Preferred Over “Disease”
The shift from “STD” to “STI” isn’t just about language—it’s about accuracy and reducing stigma. The word “disease” implies that someone is visibly sick or has symptoms. But many STIs don’t cause any symptoms at all, especially in the early stages. A person can have an infection, and pass it on to others, without even knowing they have it.
“Infection” is a broader, more inclusive term that captures both symptomatic and asymptomatic cases. It also helps make space for more informed conversations—ones that focus on health and prevention rather than shame. Because of this, health organizations like the CDC and WHO now use “STI” in most of their public health materials.
How Are STIs Transmitted?
STIs spread in a few different ways, but the most common route is through sexual contact. That includes vaginal, anal, and oral sex.
Primarily Through Sexual Contact
Most bacterial, viral, and parasitic STIs are passed between people during sex. Infections like chlamydia, gonorrhea, HIV, and HPV are often transmitted when body fluids or mucous membranes come into contact during intercourse. The risk increases when condoms or other barriers aren’t used, and when people have multiple or anonymous partners without regular testing.
Skin-to-Skin Contact
Some STIs don’t require penetration to spread. Herpes and certain strains of HPV can be passed through direct skin-to-skin contact with infected areas. This means they can be transmitted even if condoms are used, since condoms may not cover all areas of potential exposure. While barrier protection still reduces the risk, it’s important to know that it’s not 100% foolproof for every type of STI.
Other Modes of Transmission
While sex is the most common way STIs are transmitted, it’s not the only one.
Mother-to-child transmission, also known as vertical transmission, can occur during pregnancy, childbirth, or breastfeeding. Infections like syphilis, HIV, and herpes can be passed from parent to baby, sometimes leading to serious complications like congenital infections or pregnancy loss.
Blood contact and needle sharing are also transmission routes for certain STIs. HIV and hepatitis B, for example, can be spread through shared needles or unscreened blood products. Thanks to improved safety protocols and screening, the risk from blood transfusions is now extremely low in many parts of the world—but the risk from shared drug equipment remains real.
The Most Common STIs (and What Causes Them)
When people ask what are STIs, they’re usually trying to understand which infections are most common, how they spread, and what they actually do in the body. STIs are caused by a range of organisms—including viruses, bacteria, and parasites—and each one affects the body differently. Some may cause visible symptoms; others might go unnoticed for months or even years. Here’s a breakdown of the most common STIs grouped by what causes them.
Viral STIs
Viral infections cannot be cured, but many can be managed with medication and regular healthcare.
Herpes Simplex Virus (HSV-1 & HSV-2)
Herpes is one of the most well-known viral STIs.
- HSV-1 typically causes cold sores around the mouth but can also infect the genitals through oral-genital contact.
- HSV-2 is primarily associated with genital infections and spreads through vaginal, anal, or oral sex—often even when no symptoms are present. This is known as asymptomatic shedding, and it’s one reason herpes is so easily passed between partners.
Human Papillomavirus (HPV)
HPV is the most common STI in the world, with over 100 known types.
- Many people will contract it at some point in their lives without ever knowing it.
- Certain high-risk strains are linked to cancers, including cervical, anal, and penile cancer.
- HPV spreads through skin-to-skin contact, often during vaginal or anal sex, and most people clear the infection naturally.
Human Immunodeficiency Virus (HIV)
HIV affects the immune system, making it harder for the body to fight off infections.
- It spreads through vaginal, anal, or oral sex, as well as blood contact and from mother to child during childbirth or breastfeeding.
- Without treatment, HIV can lead to AIDS, but with proper care, people with HIV can live long, healthy lives.
Hepatitis B Virus (HBV)
Hepatitis B causes inflammation of the liver and is spread through sexual contact, blood exposure, and during childbirth.
- Chronic infection can lead to serious liver conditions such as cirrhosis or cancer.
- Vaccination is available and widely recommended to prevent HBV infection.
Bacterial STIs
Bacterial infections are typically curable with antibiotics, though early detection and treatment are important to prevent complications.
Chlamydia
Caused by Chlamydia trachomatis, chlamydia is one of the most common and often silent STIs.
- Many people, especially women, experience no symptoms.
- If untreated, it can lead to pelvic inflammatory disease (PID), ectopic pregnancy, and infertility.
Gonorrhea
This infection is caused by Neisseria gonorrhoeae and can affect the genitals, rectum, and throat.
- Like chlamydia, it often presents without symptoms.
- One growing concern is that some strains of gonorrhea are becoming resistant to standard antibiotics, making treatment more complicated.
Syphilis
Syphilis, caused by Treponema pallidum, progresses through several stages: primary, secondary, latent, and tertiary.
- In its early stages, it may cause painless sores or rashes that go away on their own.
- Without treatment, however, it can cause serious damage to the brain, heart, and other organs over time.
Parasitic STIs
Parasitic infections are less common but still important to understand. These are usually treatable with medications and good hygiene.
Trichomoniasis
This STI is caused by the parasite Trichomonas vaginalis.
- Many people don’t experience symptoms, but when they do, it may cause itching, unusual discharge, and discomfort during urination or sex.
- It’s one of the most common non-viral STIs.
Pubic Lice (Crabs)
Pubic lice are tiny insects (Pthirus pubis) that live in coarse body hair, including the pubic area.
- They spread through close physical or sexual contact and cause itching and visible lice or eggs in the hair.
Scabies
Scabies is caused by a microscopic mite (Sarcoptes scabiei) that burrows into the skin.
- It spreads through prolonged skin-to-skin contact, including during sex, and causes intense itching and a rash.
- Though not exclusive to sexual transmission, it’s considered an STI when spread this way.
Why You Might Not Know You Have One
One of the most challenging things about sexually transmitted infections is that they often don’t announce themselves. Many people associate STIs with clear symptoms or visible signs, but in reality, most infections start out silently—or mimic other, less concerning conditions. This makes it easy to carry and pass on an STI without ever realizing it.
Many STIs Have No Symptoms—or Symptoms That Are Easily Mistaken for Something Else
A large number of STIs are asymptomatic, especially in the early stages. Chlamydia, gonorrhea, and HPV frequently go unnoticed, particularly in people with vaginas, where symptoms might be subtle or entirely absent. Even when signs do appear, they can look and feel like something else. Discomfort during urination, unusual discharge, or itching might be brushed off as a yeast infection, urinary tract infection, or just general irritation.
Because of this, many people delay getting tested or treated, not out of neglect, but because they genuinely don’t know there’s anything wrong. Unfortunately, those delays can lead to serious complications down the line—like infertility, chronic pelvic pain, or ongoing infections that are harder to manage.
Asymptomatic Infections and Unintentional Transmission
When someone has an STI but no symptoms, it’s called an asymptomatic infection. Depending on the type of STI, this symptom-free period can last for weeks, months, or even years. During that time, the infection can still be passed on to others—without anyone knowing it’s happening.
This is particularly true for infections like HIV, chlamydia, gonorrhea, and herpes. In fact, a significant amount of STI transmission occurs from people who don’t even realize they’re infected. Asymptomatic carriers can unknowingly pass the infection to partners, especially in communities where testing isn’t easily accessible or where stigma prevents open conversations about sexual health.
Understanding this reality is a key part of STI literacy. When people ask what are STIs, it’s important to recognize that not all infections come with a warning sign—and that lack of symptoms doesn’t mean there’s no risk.
The Importance of Regular Testing—Even If You Feel Fine
The only way to know for sure if you have an STI is to get tested. Routine screening is a simple but powerful tool that helps catch infections early, often before symptoms ever show up. This is especially important for anyone who is sexually active, and even more so for those with new or multiple partners.
Early detection matters. It can prevent long-term health problems, protect future fertility, and reduce the chance of passing an infection to someone else. That’s why public health guidelines recommend regular STI testing, particularly for young adults, men who have sex with men, and others who may be at higher risk.
You don’t need to wait for something to feel “off” before getting checked. In fact, making testing a routine part of your health care—just like a dental visit or a yearly checkup—is one of the most responsible and caring things you can do for yourself and for the people you’re intimate with.
How to Protect Yourself and Others
Understanding what STIs are is only part of the picture—knowing how to protect yourself and others is just as important. STI prevention isn’t about perfection or fear. It’s about making informed choices, reducing risk where you can, and looking out for yourself and the people you’re close to. There’s no one-size-fits-all approach, but three key strategies stand out: using protection, getting tested regularly, and having open conversations.
Use Protection
Condoms and dental dams are some of the most effective tools we have for reducing the risk of STI transmission.
- Male and female condoms provide strong protection against infections spread through bodily fluids, like chlamydia, gonorrhea, and HIV.
- Dental dams—a thin barrier used during oral sex—can reduce the risk of transmission between the mouth and genitals or anus.
- It’s important to note that barrier methods don’t offer full protection against infections that spread through skin-to-skin contact, such as herpes or HPV, since these may affect areas not covered by a condom.
Protection works best when it’s used consistently and correctly. That means checking expiration dates, using a new condom every time, and making sure it’s applied properly. Even small mistakes—like putting one on too late or using it incorrectly—can reduce its effectiveness. Being intentional about protection is a simple yet powerful way to take control of your sexual health.
Get Tested Regularly
Even if you feel fine, regular STI testing should be part of your routine if you’re sexually active.
- Because many STIs don’t cause noticeable symptoms, testing may be the only way to know if you or a partner has one.
- How often you get tested depends on your level of risk. If you have new or multiple partners, don’t always use condoms, or belong to a group with higher STI rates, you may need to get screened more frequently.
Early testing helps prevent complications such as pelvic inflammatory disease, infertility, and the risk of passing an infection to a partner or newborn. Public health experts generally recommend annual screening for sexually active people under 25, and more frequent testing for higher-risk individuals. If you’re unsure what’s right for you, a healthcare provider can help tailor a schedule that fits your situation.
Talk Openly
Communication is one of the most powerful—and often overlooked—tools for STI prevention.
- Talking to partners about STI status, testing history, and safer sex practices helps build trust and mutual understanding.
- These conversations may feel awkward at first, but they’re essential for making informed decisions together. Being upfront about what you know (or don’t yet know) creates space for honesty, accountability, and shared responsibility.
Discussing protection, setting boundaries, or even planning to get tested together can strengthen your connection and reduce the chances of miscommunication. Over time, these talks become easier—and they help normalize the idea that sexual health is something worth talking about openly and without judgment.
Common Myths About STIs
Even though STIs are incredibly common, misinformation about them still runs deep. These myths don’t just create confusion—they also contribute to stigma, delay diagnosis, and make it harder for people to take care of themselves and their partners. Here are a few of the most widespread misunderstandings, and the facts that can help set the record straight.
“You can tell who has an STI by looking”
This is one of the most persistent myths about sexually transmitted infections. In reality, you can’t tell whether someone has an STI just by looking at them. Most STIs don’t cause visible symptoms, especially in their early stages. Many people feel perfectly healthy and show no outward signs, even while carrying infections like chlamydia, gonorrhea, or herpes.
Even infections that can cause visible symptoms—such as genital sores or rashes—might not appear at all, or may show up in places that aren’t easily seen. Relying on appearance alone is not only unreliable—it can give people a false sense of safety.
“STIs only affect ‘promiscuous’ people”
Another common myth is that STIs only happen to people who have a lot of sexual partners. The truth is, anyone who is sexually active can get an STI, even from just one unprotected encounter.
STIs are infections, not a reflection of someone’s values, character, or relationship style. They affect people across all ages, identities, and relationship types. Even people in monogamous relationships can contract an STI if one partner has an undiagnosed infection from a previous partner. Judging someone’s risk based on their lifestyle or assumptions about their behavior only adds unnecessary shame—and keeps important conversations from happening.
“If I don’t have symptoms, I don’t have an STI”
This myth is especially dangerous because it can delay testing and treatment. Many STIs—such as chlamydia, gonorrhea, and HPV—often don’t cause noticeable symptoms, particularly in women. People may carry these infections for months or even years without realizing anything is wrong.
But even without symptoms, STIs can still be transmitted to others and may lead to serious long-term health issues, including infertility or cancer. Being symptom-free doesn’t mean you’re STI-free—which is why regular testing is so important, regardless of how you feel.
What Happens If You Test Positive?
Finding out you have an STI can bring up a mix of emotions—fear, guilt, confusion, maybe even shame. But it’s important to know that a positive test result doesn’t define you. STIs are medical conditions, not moral judgments, and most are either fully treatable or highly manageable with the right care.
Most STIs Are Treatable or Manageable
If you test positive for a bacterial STI like chlamydia, gonorrhea, or syphilis, the good news is that these infections are usually curable with a short course of antibiotics. Prompt treatment not only clears the infection but also reduces the chance of long-term health complications like pelvic inflammatory disease, infertility, or organ damage.
Viral STIs such as herpes or HIV aren’t curable, but they can be effectively managed with antiviral medications. These treatments help control symptoms, lower the risk of passing the virus to others, and support long-term health. Many people living with viral STIs lead full, healthy lives with the help of regular care and treatment.
What Happens Next?
After a positive result, your healthcare provider will likely walk you through immediate treatment options or refer you to a specialist if needed. Some infections require specific drug regimens or follow-up care to ensure the treatment is working.
In many cases, you’ll be asked to return for retesting—usually within a few months—to confirm that the infection has cleared. This is especially common for chlamydia and gonorrhea, where reinfection can happen if a partner hasn’t been treated as well.
You’ll also be encouraged to notify any current or recent sexual partners so they can get tested and treated if necessary. This might feel uncomfortable, but it’s an important step in stopping the spread of infection. Many health clinics offer confidential partner notification services to make this process easier and more private.
Compassion Matters—For Yourself and Others
Testing positive for an STI can be emotionally tough. Some people feel shame, guilt, or fear of being judged. But you are not alone, and you’re not to blame for having an infection. STIs are incredibly common, and getting tested is a responsible, caring act.
Being kind to yourself in this moment is just as important as taking care of your physical health. It’s okay to seek support—from a friend, counselor, or support group—if you’re feeling overwhelmed.
And when someone else shares their STI status with you, meet them with the same compassion you’d hope for. Understanding what STIs are means recognizing them as part of the broader human experience—not something that makes anyone less worthy of respect, intimacy, or care.
STI Prevention Is About Empowerment—Not Fear
Too often, conversations about sexually transmitted infections have been framed around fear and shame. But that approach doesn’t help people make healthy choices—in fact, it often does the opposite. When we talk about what are STIs, we also need to talk about how we can prevent them in a way that’s grounded in knowledge, self-respect, and care for others.
Informed Choices Over Shame
STI prevention isn’t about being perfect—it’s about being informed. That means understanding how infections are transmitted, knowing how to protect yourself, and feeling comfortable getting tested when needed. Fear-based messages may grab attention, but they often lead to silence, anxiety, and avoidance. What actually works is access to clear information, supportive services, and nonjudgmental care.
Public health guidance has evolved to reflect this. Today, there’s a stronger focus on using respectful, inclusive language that supports health autonomy and personal agency. The goal is to give people the tools they need to make confident, empowered decisions—not to scare or shame them into silence.
Normalize Sexual Health Conversations in Relationships
Talking about STIs with a partner doesn’t have to be awkward or confrontational. In fact, it can be a meaningful step toward building trust, setting shared expectations, and protecting each other’s health. Discussing things like testing history, condom use, and boundaries should be as normal as talking about contraception or any other aspect of a healthy sexual relationship.
When these conversations are part of a relationship from the start, they become easier and more routine. It creates space for honesty, care, and mutual decision-making—no judgment, just understanding.
The More We Talk, the Less Stigma Holds Power
Stigma thrives in silence. When people feel judged for having or even asking about STIs, they’re less likely to get tested, talk to their partners, or seek care. That’s why breaking the silence around sexual health is such a powerful act.
The more we talk openly—whether it’s in relationships, in public health campaigns, in classrooms, or online—the more we reduce the shame that still clings to this topic. And when stigma fades, people are more likely to access testing, treatment, and information without fear. That’s how we move from fear-based messaging to real, lasting prevention: by meeting people where they are, with compassion and clarity.
Understanding STIs Means Taking Care of Yourself and Others
Sexually transmitted infections are a normal part of human health. They’re common, often treatable, and nothing to be ashamed of. But because STIs are still surrounded by stigma and misinformation, many people are left confused or afraid to ask questions. That’s why understanding what STIs are—how they’re transmitted, how to prevent them, and what to do if you test positive—is such an important part of caring for yourself and the people around you.
Knowledge isn’t just power—it’s kindness. When we replace silence with honest conversation, judgment with support, and fear with information, we make it easier for everyone to stay healthy. STI prevention doesn’t require perfection. It starts with small steps: using protection, getting tested regularly, and talking openly with partners.
If you found this guide helpful and want to keep learning about sexual health in a thoughtful, stigma-free way, we invite you to join our mailing list. You’ll get updates, resources, and tools to help you stay informed and empowered—no pressure, no judgment, just real support.
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