What are Sexually Transmitted Diseases (STDs?)

What are STDs?

Sexually transmitted diseases (STDs) are infections passed from person to person through sexual contact, including vaginal, oral, or anal sex. Sometimes known as sexually transmitted infections (STIs), some of these diseases can also rarely be passed on through intimate skin-to-skin contact.

STDs are very common, with millions of new cases occurring in the U.S. every year. STDs can affect anyone who is sexually active — both men and women of all ages can contract a sexually transmitted disease.

Types of STDs


There are many types of STDs caused by viruses, bacteria, and parasites. Every type of sexually transmitted disease presents with different symptoms (or none at all) and requires a different treatment.

Some common STDs include:

  • HIV/AIDS. Human immunodeficiency virus (HIV) is a sexually transmitted disease that can cause acquired immunodeficiency syndrome (AIDS). AIDS is a chronic condition that occurs when HIV significantly damages the immune system.
  • Genital herpes. This condition is caused by two types of viruses — herpes simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2). These viruses can cause outbreaks of blisters around the genitals and rectum.
  • Syphilis is a bacterial infection that often remains in the body without causing symptoms, but can eventually cause severe damage to the body’s organs if left untreated.
  • Chlamydia is a common STD that can remain in the body without causing symptoms and potentially permanently damage the female reproductive system if left untreated.
  • Gonorrhea is a bacterial STD that can cause no symptoms or, most commonly, symptoms occurring along the genital tract.
  • Trichomoniasis. This STD is caused by a parasite that can cause painful urination, foul-smelling vaginal discharge, and genital itching in women.
  • Hepatitis B is a liver infection caused by the hepatitis B virus, which can be transmitted through sexual contact. Hepatitis B may not cause symptoms but may cause stomach pain, fatigue, jaundice, and poor appetite.

Signs & Symptoms of STDs


Every STD can present with different symptoms, or in many cases, no symptoms. Since so many STDs can remain in the body for years without causing symptoms, regular STD testing is important for anyone who is sexually active. Some STDs can cause serious or permanent damage to the body if left untreated, even if they never cause symptoms.

When STDs do cause symptoms, common ones include:

  • Swelling, itching, or pain in the genitals
  • Unusual genital discharge
  • Bumps or sores on or around the genitals
  • Skin rash
  • Painful or frequent urination
  • Fever
  • Fatigue
  • Abdominal pain
  • Weight loss

Pregnancy and STDs

Pregnant women are at risk for contracting STDs the same way women who are not pregnant are. Women who are infected with an STD and become pregnant are also at risk for certain complications that can affect the pregnancy and birth of their baby. STD testing during pregnancy is essential, as the sooner you begin receiving treatment for an STD while pregnant, the better chance you have of avoiding serious complications. Some STDs, like chlamydia and syphilis, are treated with safe antibiotics during pregnancy.

Many STDs, including gonorrhea, hepatitis B, herpes and chlamydia, can pass from mother to baby as the child passes through the birth canal. Others, including HIV and syphilis, can cross through the placenta and infect the baby in the womb.

How are STDs Transmitted


STDs are mainly transmitted through sexual intercourse but can be passed from person to person in additional ways as well. Some STDs can spread by sharing needles or syringes while injecting intravenous drugs, through blood transfusions, or by skin-to-skin contact. Many STDs can pass from mother to baby during pregnancy.

The viruses, bacteria, and parasites that cause STDs can be transmitted through:

  • Semen and vaginal secretions
  • Saliva
  • Blood
  • Contact with open sores or warts on the mouth or genitals

A primary care physician, OB/GYN, or pediatrician can help you understand how and when individual STDs can be contracted. It’s important to schedule regular check-ups and STD testing to stay on top of your health.

Risk Factors for STDs

Risk Factors

Anyone who is sexually active is at risk of contracting an STD. Those practicing unprotected sex or having sex with multiple sexual partners further increase their risk of catching or spreading an STD. Those with a history of STDs are more likely to contract one in the future, and using intravenous drugs or sharing needles will also increase your chances of developing an STD.



Many STDs are easily treatable if caught early, and those without cures can be managed with various therapies and medications. However, if allowed to progress, STDs can cause significant health problems or complications ranging in severity from mild to life-threatening.

Complications that can arise following infection with an STD include:

How to Prevent STDs


The only way to completely avoid sexually transmitted diseases is to abstain from sexual activity and avoid using intravenous drugs. However, there are several ways to engage in sexual activity but limit your likelihood of contracting an STD.

These include:

  • Using condoms and dental dams
  • Sexual activity with one uninfected partner
  • Vaccination against human papillomavirus (HPV and hepatitis B)
  • STD testing prior to sexual activity with a new sexual partner
  • Avoiding excessive alcohol consumption and drug use, which can make risky sexual activity more likely

Regular testing and understanding the signs and symptoms of STDs can make it more likely you catch any potential infections early when they are more easily treated.

Get Care

Trust NewYork-Presbyterian for STD care

At NewYork-Presbyterian, our sexual health experts can help you understand the risk factors for STDs, get tested regularly, and promptly treat any conditions that may arise. Through an in-person or video* appointment at NewYork-Presbyterian or one of our medical group locations, our team can guide you through your treatment options and ensure you feel empowered to make decisions about your sexual health.

*Restrictions apply