Sexually transmitted infections (STIs) are infections caused by bacteria, viruses, yeasts, or parasites and are spread through intimate sexual contact involving the penis, vagina, mouth, or anus. STDs are also called venereal disease (VD) or sexually transmitted diseases (STDs).
The term "infection" is often used rather than "disease" because it is possible for a person to have no symptoms but still carry the infection and require treatment
Most STIs affect both men and women, but the medical problems are often more severe for women. An STI during pregnancy, it can cause serious problems for the baby.
Correct usage of latex condoms greatly reduces, but does not completely eliminate, the risk of catching or spreading sexually transmitted infections.
Different Types of STIs
There are more than 20 different kinds of sexually transmited infections, which can fall into two main groups:
Sexually transmitted diseases caused by bacteria
These diseases can be treated and often cured with antibiotics. Some bacterial infections include:
- Chlamydia is a common STI caused by the bacterium Chlamydia trachomatis. While many individuals will not experience symptoms, chlamydia can cause fever, abdominal pain, and unusual discharge of the penis or vagina. In women, whether or not they are having symptoms and know about their infection, chlamydia can cause pelvic inflammatory disease (PID) and lead to permanent damage to the woman's reproductive organs.
- Gonorrhea is caused by the bacterium Neisseria gonorrhoeae, which can grow rapidly and multiply easily in the warm, moist areas of the reproductive tract. The most common symptoms of gonorrheal infection are a discharge from the vagina or penis and painful or difficult urination. As with chlamydial infection, the most common and serious complications of gonorrhea occur in women and include pelvic inflammatory disease (PID), ectopic pregnancy, infertility, and the potential spread to the developing fetus if acquired during pregnancy.
- Syphillis infections, caused by the bacterium Treponema pallidum, are passed from person to person during vaginal, anal, or oral sex through direct contact with sores, called chancres. The first sign of syphilis is a chancre, a painless genital sore that most often appears on the penis or in and around the vagina. These sores typically resolve on their own, even without treatment. However, the body does not clear the infection on its own, and, over time, syphilis may spread to other organs.
- Trichomoniasis infection is caused by the single-celled protozoan parasite Trichomonas vaginalis and is common in young, sexually active women. The parasite also infects men, though less frequently. The parasite can be transmitted between men and women as well as between women whenever physical contact occurs between the genital areas. While Trichomonas infections do not always cause symptoms, they can cause frequent, painful, or burning urination in men and women as well as vaginal discharge, genital soreness, redness, or itching in women.
Sexually transmitted diseases caused by viruses
These diseases can be controlled, but not cured. If you get a viral STI, you will always have it. Some viral STIs include:
- HIV or the human immunodeficiency virus, is the virus that causes AIDS (acquired immunodeficiency syndrome). HIV destroys the body's immune system by killing the blood cells that fight infection. Once HIV destroys a substantial proportion of these cells, the body's ability to fight off and recover from infections is compromised. This advanced stage of HIV infection is known as AIDS. Transmission of the virus primarily occurs during unprotected sexual activity and by sharing needles used to inject intravenous drugs, although the virus also can spread from mother to infant during pregnancy, delivery, and breastfeeding.
- Genital herpes is a contagious infection caused by the herpes simplex virus (HSV). There are two different strains of HSV: herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2). Both can cause genital herpes, although most cases of genital herpes are caused by HSV-2. When symptomatic, HSV-1 usually appears as fever blisters or cold sores on the lips, but it can also infect the genital region through oral-genital or genital-genital contact. Symptomatic HSV-2 typically causes painful, watery skin blisters on or around the genitals or anus. However, substantial numbers of people who carry these viruses have no or only minimal signs or symptoms. Neither HSV-1 nor HSV-2 can be cured, and even during times when an infected person has no symptoms, the virus can be found in the body's nerve cells. Periodically, some people will experience outbreaks in which new blisters form on the skin in the genital area; at this time, the virus is more likely to be passed on to other people.
- Genital warts caused by human papilloma virus (HPV). Human papilloma virus7 (HPV) is the most common STI. More than 40 HPV types exist, and all of them can infect both men and women. The types of HPVs vary in their ability to cause genital warts; infect other regions of the body, including the mouth and throat; and cause cancers of the cervix, vulva, penis, and mouth. Although no cure exists for HPV infection once it occurs, regular screening with a Pap smear test can prevent or detect at an early stage most cases of HPV-caused cervical cancer. A newly available vaccine protects against most (but not all) HPV types that cause cervical cancer.
- Viral Hepatitis A (HAV) causes a short-term or self-limited liver infection that can be quite serious, although it does not result in chronic infection. While there are other ways the virus can be transmitted, HAV can be spread from person to person during sexual activity through oral-rectal contact. Vaccination can prevent HAV infection.
- Viral Hepatitis B (HBV) causes a serious liver disease that can result in both immediate illness and lifelong infection leading to permanent liver scarring (cirrhosis), cancer, liver failure, and death. HBV spreads through both heterosexual and homosexual contact as well as through contact with other bodily fluids, such as blood, through shared contaminated needles used for injecting intravenous (IV) drugs, tattooing, and piercing. Pregnant women with HBV can transmit the virus to their infants during delivery. HBV infection is preventable through vaccination.
- Viral Hepatitis C (HCV) can cause an immediate illness affecting the liver, but it more commonly becomes a silent, chronic infection that leads to liver scarring (cirrhosis), cancer, liver failure, and death. HCV is most commonly transmitted through sharing needles or exposure to infected blood. However, it can spread through sexual contact or from mother to fetus during pregnancy and delivery. There is no vaccine for hepatitis C, and treatments are not always effective.
Symptoms of Sexually Transmitted Infections
The symptoms vary among the different types of STIs. Some examples of common symptoms include:
- Unusual discharge from the penis or vagina
- Sores or warts on the genital area
- Painful or frequent urination
- Itching and redness in the genital area
- Blisters or sores in or around the mouth
- Abnormal vaginal odor
- Anal itching, soreness, or bleeding
- Abdominal pain
In some cases, people with STIs may not feel ill, and over time the symptoms can improve on their own. However, it is common for individuals to have an STI and pass it on to others without knowing it.
If you are concerned that you or your sexual partner may have an STI, talk to your health care provider. Even if you do not have symptoms, it is possible you may have an STI that needs to be treated to ensure your and your partner's sexual health.
Prevention of STIs
The most reliable ways to avoid STIs are to abstain from sexual contact or to be in a long-term monogamous relationship with a partner who has been tested and is uninfected.1 In addition, you can take the following measures to avoid STIs:
- Know your sexual partner's STI and health history.
- Talk to your health care provider about your risk, and get tested for STIs.
- Get vaccinated against hepatitis A virus (HAV), hepatitis B virus (HBV), and human papilloma virus (HPV).
Another important way to avoid getting an STI is to use latex condoms correctly for vaginal, oral, and anal intercourse EVERY TIME. Remember, however, that while condoms greatly reduce the chance of getting certain STIs, such as genital herpes, condoms cannot fully protect against infection because viruses and some bacteria can be passed from person to person by skin-to-skin contact in the genital area not covered by a condom.
Treatments for STIs
STIs caused by bacteria, yeast, or parasites can be treated with antibiotics. These antibiotics are most often given by mouth (orally). However, sometimes they are injected or applied directly to the affected area. Whatever the infection, and regardless of how quickly the symptoms resolve after beginning treatment, the infected person must take all of the medicine prescribed by the health care provider to ensure that the STI is completely treated.
Viruses such as HIV, genital herpes, HPV, hepatitis, and cytomegalovirus cause STIs that cannot be cured. People with an STI caused by a virus will be infected for life and will always be at risk of infecting their sexual partners, although for many viruses treatment significantly reduces this risk.
Although treatments, complications, and outcomes vary among viral STIs depending on the particular virus (HIV, genital herpes, HPV, hepatitis, or cytomegalovirus), health care providers can provide treatments to reduce the symptoms and the progression of most of these illnesses. For example, medications are available to limit the frequency and severity of genital herpes outbreaks while reducing the risk that the virus will be passed on to other people.
What to do if diagnosed with an STI
You should see your health care provider for treatment as soon as possible after receiving a diagnosis of an STI. You also should notify, either yourself or with the help of the local health department, all recent sex partners and advise them to see their health care providers and be treated. These steps will reduce your risk of becoming re-infected, help avoid spreading the STI to other people, and decrease the risk that your previous sexual partners will develop serious complications from the STI. You and all of your sex partners must avoid sex until treatment is complete and all symptoms have disappeared.
In the case of STIs caused by viruses with no cure (for example, HIV, genital herpes, or hepatitis), special care and preventive measures can help control the infection, limit symptoms, and help maximize health.
Reference: National Institutes of Child Health and Human Development