Guide to Sexually Transmitted Diseases

Reported cases of sexually transmitted infections in the United States have been on the rise in the past two decades, and rates in the U.S. are among the highest in high-income countries globally. Approximately, 1 in 5 people in the U.S. had an STI at any given day in 2018, according to a 2021 report from the Centers for Disease Control and Prevention.

“One of the root causes for this extraordinarily high prevalence and very high morbidity related to these diseases is because of stigma,” says Dr. Edward W. Hook III, an emeritus professor of medicine of infectious diseases at the University of Alabama at Birmingham.

Getting comfortable talking about sex and all that comes with it — the good, bad and the ugly — is important to breaking down the stigma.

[SEE: 13 Tips for a Mammogram.]

What Are STDs?

Although the terms sexually transmitted diseases and STIs are often used interchangeably, they don’t exactly mean the same thing.

An STD refers to the actual disease state that develops due to infection — meaning the infection causes damage to the body and/or leads to illness, whereas an STI refers to a pathogen that enters the body and causes infection through sexual contact, such as genital sex, oral sex or anal sex.

STDs can be stigmatizing because they’re not necessarily always diseases and don’t always end in bad outcomes, says Dr. Patricia Kissinger, a professor of epidemiology at Tulane University School of Public Health and Tropical Medicine.

“It’s less stigmatizing to call it STI rather than STD,” Kissinger says.

Some STIs can be transmitted from mother to child, as well. When that happens, the pregnant person acquires the infection through sex, then they can also pass it on to their child.

“They can spread rarely through intimate physical contact and body fluid exchange,” says Dr. George Jour, a board-certified pathologist affiliated with NYU Langone Hospitals in New York and Cooper University Health Center in Camden, New Jersey, and advisory board member and clinical consultant at Innovative Health Diagnostics, a lab that offers at-home STD tests.

[SEE: Health Screenings You Need Now.]

Symptoms of STIs

Symptoms of STI vary. They can range from completely asymptomatic, meaning no visible symptoms, to genital skin manifestation.

Symptoms of the most common STIs may include:

— Rednesss, especially sudden redness of the vulva or vagina, and possibly new swelling or rash.

— Vesicles, papules or warty lesions that can be itchy, burning, red and oozing or can present as ulcerated and non-painful lesions.

— Secretion, or discharge, of fluid from the genitals.

Burning during urination.

— Fever, especially accompanied by pelvic pain.

— Sore throat, particularly after oral sex.

— Suddenly enlarged lymph nodes in the groin.

[SEE: Breast Cancer Symptoms.]

Types of STIs

There are more than 30 different bacteria, viruses and protozoans for which sexual transmission is the main mechanism of transmission.

Other infections that are sometimes transmitted through sex include the Zika virus, Ebola virus or mpox, but they are not considered STIs.

Common types of STIs include:

— Chlamydia.

— Gonorrhea.

— Syphilis.

— Herpes.

— HPV.

— HIV.

— Hepatitis A, B and C.


Chlamydia is the most common bacterial STI in the United States, Hook says. However, that’s not a new trend. According to the CDC, chlamydia has made up the largest reported number of STIs in the U.S. since 1994.

Chlamydia is largely asymptomatic in both sexes. Therefore, STI screening, which typically happens during either an annual reproductive health visit or primary care visit, is important for diagnosing this infection.

Untreated chlamydia can lead to both short- and long-term health complications. In women, untreated chlamydia can spread to the uterus and fallopian tubes, causing pelvic inflammatory disease. PID can lead to chronic pelvic pain, infertility and ectopic pregnancy, which is when the egg fertilizes outside of the uterus and can cause life-threatening internal bleeding, damage to surrounding organs and/or death to the fetus. Because of its prevalence and potential health complications, chlamydia is often routinely tested for in any sexually active adult.


In 2020, the most recent year for which there’s comprehensively reported surveillance data available, the CDC reported nearly 680,000 cases of gonorrhea in the U.S., making it the second most common STI in the U.S.

Similar to chlamydia, gonorrhea is a bacterial STI that often exhibits no signs or symptoms of infection but is easily treated. It’s also routinely tested for because of how common it is.

Untreated gonorrhea can cause serious health problems, according to the CDC. In women, untreated gonorrhea can cause PID, which may lead to complications like scar tissue that blocks the fallopian tubes, ectopic pregnancy or infertility. In men, gonorrhea can cause a painful condition in the tubes attached to your testicles or sterility in rare cases.


Syphilis is a genital ulcerative disease, meaning you’ll likely have visible sores on your body. Sores occur where the infection entered your body, which could be in, on or around your genital area, anus or rectum and the lips or mouth. It can also cause lesions on the palms and feet, even while patients do not “feel sick”. Unfortunately, this infection is on the rise again, and it can lie dormant for a while.

Without treatment, syphilis can progress to what’s called “tertiary syphilis” and affect different organs in your body, including the heart, blood vessels, the brain and nervous system, which can result in death. According to the CDC, most people with syphilis do not go on to develop tertiary-stage syphilis, and in cases where it does occur, it’s typically 10 to 30 years after your initial infection. Because of its increased prevalence, it is recommended that even basic STI testing includes an RPR, the screening test for syphilis.


Herpes is categorized into two types: genital herpes and oral herpes. Herpes affects the peripheral nervous system by injecting its genetic code directly into the nucleus of a neuron and instructing cells to produce more herpes viruses.

Herpes is often asymptomatic or mildly symptomatic. Herpes presents physically as sores, usually as one or more blisters in or around the mouth, genitals or rectum. You can treat symptoms of herpes with medicines that prevent or shorten outbreaks, but you can’t cure it. The infection remains in the neurons and will manifest when a person is stressed. Some people experience recurrent outbreaks and take suppressive antiviral medication.

STI blood testing is optional for herpes. Type 1 herpes simplex, which most often results in the cold sore symptoms, is very common. Type 2 herpes simplex is more often a genital infection and can be pretty severe. Many adults have positive antibodies for type 1 and many for type 2 herpes simplex, even without previous symptoms.

Human papillomavirus (HPV)

There are approximately 150 types of HPV identified, at least 40 of which can cause infections to the genital area, according to the CDC. A majority of HPV infections are asymptomatic, showing no signs of infection.

HPV is thought to be responsible for nearly all cases of cervical cancer, about 70% of vaginal and vulvar cancers and 60% of penile cancers, according to the CDC. HPV types 16 and 18 cause a majority of cervical, penile, vulvar, vaginal, anal and oropharyngeal cancers and precancers.

HPV was extraordinarily widespread until the development of a vaccine. Prior to the vaccine, an estimated 80% to 90% of the population would have one or more HPV infections during their lifetime, Hook says. Only a tiny percentage — less than 1% — would go on to develop cancer, he adds.

“The vaccine is highly protective for both the HPV types which cause most visible warts — and are not a meaningful risk factor for cancer — and those which cause the majority of genital cancers,” Hook says. “With increasing prevalence of vaccinations, the prevalence of these infections, as well as precancerous lesions has declined.”

Human immunodeficiency virus (HIV)

HIV is a virus that attacks the body’s immune system and can lead to AIDS, or acquired immunodeficiency syndrome, if left untreated.

“HIV is largely asymptomatic,” Kissinger says. “Only about 30% of people that have an acute HIV infection actually show symptoms.”

Many experience flu-like symptoms within the first two to four weeks of infection. Though recent headlines may show treatment promise, there is currently no cure for HIV.

If you feel like you are potentially at risk for HIV, or even if you don’t know, you should consult with your health provider because they can get you on something called pre-exposure prophylaxis, or PrEP, Kissinger says. PrEP would protect you from getting HIV, she says. “It’s sort of analogous to a vaccine for HIV, but you have to take it every day.”

Hepatitis A, B and C

Hepatitis is an inflammation in the liver, in this case, caused by a virus — hepatitis A, B or C. Many with hepatitis do not experience symptoms and are not aware they are infected. For those who do experience symptoms, it may include fever, fatigue, loss of appetite, nausea and/or vomiting, abdominal pain and joint pain.

Hepatitis B and C are leading causes of liver cancer, according to the CDC. Hepatitis C is also a leading cause of liver transplants.

Hepatitis A and B can’t be treated, but there’s a vaccine available to prevent yourself from getting them, Kissinger says. With hepatitis C, there’s no vaccine but there’s a treatment available, she says.

Risks of STIs

The importance of STIs lies largely in their long-term consequences, Hook says, particularly because many of these infections are asymptomatic.

“The tragedy of STIs is that people acquire these infections while they’re relatively young and don’t suffer the consequences until years and even decades later,” Hook says.

For example, chlamydia can cause ectopic pregnancy and infertility. In men, it can cause epididymitis (inflammation at the back of the testicle) and less motility of the sperm, meaning the ability to move sperm efficiently.

“It’s causing infertility, but you don’t really know it until you get tested,” Kissinger says.

Similarly, with HPV, people who haven’t received the vaccine acquire those infections at a rate of about 30% to 40% per year after the initiation of sexual intercourse, Hook says. But cervical cancer and genital tract malignancies don’t typically occur in people until they’re in their late 30s and, oftentimes, later than that.

The separation between when people acquire their infections and when people become aware of the long-term consequences has made it particularly challenging to prevent and treat STIs in the public health field.

“Public health agencies are funded in the here and now — about what’s happening now,” Hook says.

As a result, the “economic imperative” is a little harder to see and further over the horizon, which makes it challenging for these diseases to be priorities for health care systems.

STIs and Pregnancy

Health experts encourage people to get a full STI evaluation before they conceive.

Children born to infected mothers can have those infections and suffer long-term consequences, or the infections themselves can cause complications of pregnancy.

Some STIs can cause complications like pneumonia, blindness or deformities in the baby. STIs are less likely to cause death, but HIV and syphilis can cause death of the baby, Kissinger says.

“It’s best to get tested regularly, particularly if you’re having multiple partners or you’re engaging in condomless sex or you don’t know your sexual partner status,” Kissinger emphasizes.

STI Testing

Because most STIs are asymptomatic, it’s important to get tested.

“There’s nothing really to prompt a person to go get tested,” Kissinger says.

That’s why annual STI screening is so important if you’re sexually active.

“If you’re in a high-risk or high-prevalence group, you should get tested much more frequently. And particularly persons who engage in anal sex should be tested far more frequently,” Kissinger says.

Depending on your symptoms and physical exam, your doctor may take a blood or urine sample or swab the genital area, inside of the mouth or any visible sores. You can get tested in a doctor’s office or use an at-home STI testing kit in some cases.

“Since COVID, there’s been a proliferation of home tests,” Kissinger says.

Many home testing options use the same technology as testing at a physician’s office and are highly accurate, as long as there’s no user error, like taking the specimen incorrectly.

There’s nothing wrong with an at-home test, she adds, but people have to follow through if they test positive.

Kissinger emphasizes that it’s important for not only you to be seen by your doctor if you receive a positive STI test, but your sexual partners, as well, especially for treatable infections. If your sexual partners aren’t treated, they’re just going to reinfect you.

“Everybody in the sexual network has to get treated when there’s an infection introduced into the network,” Kissinger says.

STI Treatment Options

Bacterial STIs

Bacterial STIs including gonorrhea, chlamydia and syphilis are diseases where antibiotics are highly effective, Hook says. The treatment can eradicate the infection, and its potential to transmit it to other people.

“The only thing with gonorrhea is we’re seeing a lot of multi-drug resistant gonorrhea, particularly in Africa, and some of that’s coming here where they’re resistant to almost all the therapeutics we have,” Kissinger says. “Antimicrobial resistance is one of the biggest challenges in the field of STIs right now.”

Viral STIs

Viral infections like herpes and HPV are not readily cured with modern antimicrobial therapy, Hook says. They require different strategies with various medicines that effectively treat and help manage them, but viral STIs are much more of a long-term issue.

“Most of the viral infections cannot be cured,” Kissinger says.

The exception may be hepatitis C, which can be treated with an antiviral medication, which in some cases, can eradicate the infection.

Due to the lack of treatment options for some STIs, prevention becomes all the more important for those diseases.

Prevention of STIs

STI screening is an incredibly important measure to receive a diagnosis and proper treatment if you have a sexually transmitted infection and to prevent the further spread of infection to sexual partners.

“Prevention is better than dealing with the infections once you have them,” Hook emphasizes.

Luckily, there are ways you can protect yourself from sexually transmitted infections.

Sex is a usual part of life, and nearly everybody engages in it, Hook says. But STIs are the unfortunate downside of something that otherwise is a source of happiness, pleasure, a sign of intimacy and love, he says.

Condoms are one of the most effective prevention methods when used properly. Additionally, some vaccines are available that can help minimize the risk of infection, including:

Hepatitis A. There’s a hepatitis A vaccine, which is given to children, Kissinger says. Children need two doses of the vaccine, usually beginning at 12 months to 23 months of age, and receive the second dose at least six months later. Adults who weren’t previously vaccinated and want to be protected can get the vaccine.

Hepatitis B. A vaccine for hepatitis B is available, which is given to infants, Kissinger says. If an individual did not receive the vaccination as an infant, the vaccine is available for all age groups.

HPV. The HPV vaccine is recommended for adolescents at age 11 or 12, though it can be started at age 9. The vaccine was only initially recommended for people up to their mid 20s, but is now recommended for some people through age 45 or beyond in certain cases. The vaccine is given as a two- or three-dose series, depending on the individual’s age at initial vaccination. “80% to 90% of sexually active persons, if they’ve not received the vaccine, acquire HPV at some time in their life,” Hook says. Recent data shows less recurrence of cervical pre-cancer lesions in people who are vaccinated against HPV.

Any currently or previously sexually active adult should consider STI testing with their routine medical care, especially any adult with a new sexual partner or concerning symptoms.

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Guide to Sexually Transmitted Diseases originally appeared on

Update 10/10/23: This story was previously published at an earlier date and has been updated with new information.

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