Your Guide to 10 Sexually Transmitted Infections (STIs)

Sexually transmitted infections (STIs), or sexually transmitted diseases (STDs), are bacteria, viruses and parasites that can pass between people through vaginal, oral and anal sex.¹ Certain STIs may also transfer from mother to infant through pregnancy, birth or breastfeeding.²

STI cases have spiked dramatically in the United States in the last decade, and as of 2018, experts estimate that 1 in 5 Americans have an STI.³ Reported cases have only increased in recent years, partly due to the pandemic.⁴⁵ Implementing regular STI screenings and bringing more awareness to the fact that many STIs are asymptomatic are essential to mitigating these rising numbers.

Get tested in the comfort of your home with imaware's Complete STI Test. This easy and accessible at-home test screens for ten STI biomarkers: Chlamydia, Gonorrhea, Herpes Simplex Virus 1/2, Syphilis, HIV-1, HIV-2, Hepatitis B, Hepatitis C, Trichomoniasis and Mycoplasma genitalium (Mgen).

1. Chlamydia

Chlamydia is caused by an infection with Chlamydia trachomatis. It can spread through vaginal, anal and oral sex as well as from mother to child during birth. Like gonorrhea, it can infect the rectum, throat, cervix or urethra.⁶

Chlamydia is the most frequently reported bacterial STI in the United States.⁷

This "silent" infection rarely shows symptoms, with only 10% of men and 5-30% of women actually experiencing symptoms. When non-asymptomatic, symptoms of chlamydia include unusual discharge, painful or frequent urination and vaginal bleeding between periods.⁸

‍Treatment: Chlamydia is treatable with antibiotics prescribed by a healthcare professional.⁹

2. Gonorrhea

Gonorrhea is the bacterial infection of Neisseria gonorrhoeae. This STI can spread through sexual contact with the genitals, mouth or anus and from mother to infant during childbirth.¹⁰ It is one of the most commonly reported STIs in the United States — the Center for Disease Control (CDC) estimates approximately 700,000 new cases annually.¹¹

Typical areas of infection include the throat, urethra (the tube that empties urine from the bladder), rectum (end of the large intestine that leads to the anus) and, for individuals with a female reproductive system, the cervix (located at the narrow end of the uterus connecting to the vagina).^12131415

Gonorrhea can be asymptomatic and is more common in women.¹⁶ Symptoms of gonorrhea include unusual genital or anal discharge, sore throat, bleeding between periods and pain during urination, bowel movements or intercourse.¹⁷

Treatment: Gonorrhea is treatable with antibiotics prescribed by a healthcare professional.¹⁸

3. Herpes

There are two common forms of herpes: herpes simplex virus type 1 (HSV 1) and type 2 (HSV 2). 

• HSV 1 causes oral herpes, which presents as cold sores and blisters on or around the mouth. It is also possible to contract genital HSV 1 after receiving oral sex from someone with an oral HSV 1 infection.¹⁹

• HSV 2 is genital herpes, which leads to lesions or blisters in and around the genitals or anus. Typically, individuals only get HSV 2 infections through genital contact, which results in a genital HSV 2 infection.

Herpes can spread through contact with the skin in infected areas, herpes lesions, genital fluids or saliva.²⁰ It may also be passed from mother to infant during childbirth. Herpes is widespread in the United States, with an estimated 572,000 new infections annually.²¹

Other than the lesions or blisters that may appear, this STI is usually asymptomatic.

Treatment: Despite no cure for herpes, both forms are manageable with antiviral medications.²² Certain medications help reduce the frequency and severity of outbreaks and the risk of spreading to others.

4. Syphilis

Syphilis is an STI caused by the bacterium Treponema pallidum. This STI spreads through direct contact with a syphilitic sore, often during sexual intercourse.²³ The sores, or chancres, can form on the penis, vagina, anus, rectum, lips and mouth. Congenital syphilis is a form of syphilis that occurs when it is spread from mother to unborn child during pregnancy.²⁴

Rates of syphilis in the United States are rising — the CDC recorded 171,074 cases of syphilis in 2021, which is approximately 70,000 more annual cases than in 2017.²⁵

Symptoms of syphilis present in four different stages:²⁶

1. Primary stage: Single chancre appears, marking the onset of syphilis
2. Secondary stage: Skin rashes and additional lesions develop. This stage may also include fever, sore throat, swollen lymph nodes, fatigue, muscle aches and headaches.
3. Latent stage: No visible signs of syphilis
4. Tertiary syphilis: This stage can occur if syphilis is left untreated for many years and can damage multiple organ systems. In addition to tertiary syphilis, untreated syphilis can also invade the nervous system (neurosyphilis), visual system (ocular syphilis) or auditory system (otosyphilis) and have a wide range of symptoms.

Treatment: Syphilis is treatable with antibiotics prescribed by a healthcare professional.²⁷

5. HIV-1

Human immunodeficiency virus (HIV) is a serious virus that attacks the body's immune system.²⁸ The World Health Organization (WHO) estimated that 39 million people worldwide were living with HIV in 2022.²⁹ Human immunodeficiency virus type 1 (HIV-1) is the most common form of this virus, and from 2010 to 2017, approximately 99% of diagnosed HIV infections in the U.S. were HIV-1.³⁰

Transmissible through blood, semen, vaginal fluids and breast milk, HIV is typically spread through anal and vaginal sex or shared drug injection materials.³¹ It can also spread from mother to infant during pregnancy, birth or breastfeeding.

Testing for HIV is essential as some people have no symptoms and those who do typically get flu-like symptoms that are easily mistaken for other illnesses. There are three main stages of an HIV infection:³²

1. Acute infection: Within two to four weeks of infection, flu-like symptoms, such as a fever, sore throat, chills, rash, sore muscles, mouth ulcers and swollen lymph nodes, appear.
2. Chronic infection: HIV is active in the body, killing white blood cells needed to fight off infections. Individuals can use HIV treatments at this stage to help prevent progression to stage three.
3. Acquired Immunodeficiency Syndrome (AIDS): The immune system is now severely damaged, putting the body at high risk of infections and illnesses. Without treatment, individuals at this stage often only live around three years.

Treatment: There is no cure for HIV, but it is manageable with regular antiretroviral therapy (ART), a treatment that reduces the amount of HIV in the body, helping to prevent the development of AIDS.³³

6. HIV-2

Like HIV-1, human immunodeficiency virus type 2 (HIV-2) is a virus transmitted through bodily fluids that will gradually damage the body's immune system. Though similar, the genetic differences between HIV-1 and HIV-2 mean that not all tests and treatments work the same for both forms.³⁴

Compared with HIV-1, HIV-2 is classified as having a slower disease progression and less transmission efficiency.³⁵ HIV-2 is found predominantly in West Africa, and while cases of HIV-2 do exist worldwide, they are far less frequent than HIV-1.³⁶

Treatment: There is no cure for HIV, but it is manageable with regular antiretroviral therapy (ART), a treatment that reduces the amount of HIV in the body, helping to prevent the development of AIDS.³⁷

7. Hepatitis B

Hepatitis B is a liver infection caused by the hepatitis B virus (HBV), transmitted through contact with infected bodily fluids like blood, semen or vaginal fluid. According to WHO, the most common mode of HBV transmission is from mother to child during birth.³⁸ The best way to prevent HBV is to get the vaccine for it.³⁹

Hepatitis B can present as acute or chronic. Acute hepatitis B is a short-term infection — typically occurring within six months of infection — that can range from asymptomatic or mild symptoms to severe illness. Long-term infections are known as chronic hepatitis B, which can lead to severe liver damage, liver cancer and, over time, death.⁴⁰ In 2020, there were an estimated 14,000 acute cases of HBV in the U.S.,⁴¹ while the estimate for chronic HBV cases is around 880,000.⁴²

Treatment: Acute hepatitis B is often left to run its course untreated, though severe cases may require antivirals. Chronic hepatitis B infections can require life-long doses of antiviral medications or injections to reduce the risk of liver damage and passing it to others.⁴³

8. Hepatitis C

Hepatitis C is a different type of liver infection caused by the hepatitis C virus (HCV). HCV is spread through infected blood, most often through shared syringes, needles and similar equipment. However, it may be passed from mother to child during birth or through sexual activities that have blood exposure.⁴⁴ Unlike hepatitis A and B, there is no vaccine against HCV.

Like hepatitis B, HCV can have acute or chronic infections. According to WHO, around 30% of individuals with acute HCV will clear it, while 70% will develop a chronic condition.⁴⁵ Most HCV infections are initially asymptomatic, with possible symptoms appearing as a sign of advanced liver disease, including fever, nausea, exhaustion, dark urine, pale feces, and jaundice.⁴⁶

‍Treatment: Hepatitis C is typically treated with an extended course of antiviral medications prescribed by a healthcare professional and has around a 90% success rate in clearing the infection.⁴⁷

9. Trichomoniasis (trich)

Trichomoniasis, or trich, is an infection caused by the parasite Trichomonas vaginalis. This STI is much more common in women than men and is mainly found in the lower female genitalia or inside the penis. It rarely infects the mouth or anus.⁴⁸

Another commonly asymptomatic STI, only around 30% of people develop symptoms of trich.⁴⁹ Symptoms of trich that may manifest include itching or irritation of the genitals, painful urination or unusual genital discharge.⁵⁰

Treatment: Trichomoniasis is treatable with antibiotics prescribed by a healthcare professional.⁵¹

10. Mycoplasma genitalium (Mgen)

Mycoplasma genitalium, or Mgen, is a bacterium spread through vaginal or anal sex. It can infect the rectum, cervix or urethra. Research is ongoing as to whether Mgen spreads through oral sex.⁵²

Individuals with Mgen may experience unusual discharge or painful urination.⁵³ Approximately 40% of recurring cases of urethritis — inflammation of the urethra — in men are caused by MG.⁵⁴

Treatment: Mgen is treatable with antibiotics prescribed by a healthcare professional.⁵⁵

What happens if STIs are left untreated?

When STIs go untreated, they can have serious long-term health implications. STIs that cause genital inflammation or sores also increase the risk of developing other STIs like human immunodeficiency virus (HIV),⁵⁶⁵⁷ which, untreated, can lead to even more severe health complications like AIDS.⁵⁸ Here are some other possible complications of untreated STIs:

• Pelvic inflammatory disease (PID) affects those with a female reproductive system. PID can cause chronic pelvic and abdominal pain, scarred fallopian tubes, infertility and risk of pregnancy complications.⁵⁹

• Epididymitis is a complication in the sperm ducts that can cause testicular and scrotal pain, swelling, and infertility in individuals with male reproductive systems.⁶⁰

• Proctitis is the inflammation of the rectum that can cause pain, diarrhea, bleeding and discharge.⁶¹

• Urethritis is the inflammation of the urethra, with symptoms such as painful urination, genital soreness and unusual genital discharge.⁶²

• Cervicitis, which affects individuals with a female reproductive system, is the inflammation of the cervix. Though it can be asymptomatic, it may cause breakthrough bleeding, painful intercourse and abnormal genital discharge.⁶³

• Cirrhosis, caused by conditions like HBV and HCV, is severe liver scarring that prevents the liver from functioning correctly and can eventually lead to liver failure.⁶⁴

While this is not a comprehensive list of the risks of untreated STIs, it is crucial to remember the possible lasting effects and the risk of spreading to others. Regular testing helps protect you, your partners and any of their future partners.   

Pregnancy, birth and breastfeeding

There are additional risks associated with untreated STIs during pregnancy. Depending on the STI, expectant mothers may be at higher risk for miscarriage, preterm delivery, infections and stillbirths.⁶⁵ STIs passed from mother to child may put infants at a higher risk of health complications like low birth weight, life-threatening infections, developmental and physical delays, and even death.⁶⁶⁶⁷

Summary

Many STIs are asymptomatic; therefore, being symptom-free does not mean you are in the clear. It is important to remember that while most STIs are manageable with the help of antibiotics or antivirals, left untreated, they can cause lasting damage to your health and spread to others. To help prevent the spread of STIs, use protection, ensure you and your partners are getting tested and encourage others to do the same.