Sexually transmitted infections (STIs), also known as sexually transmitted diseases (STDs) or venereal diseases (VD) are diseases that are passed on from one person to another through sexual contact - the infection can be passed on through vaginal intercourse, oral sex, and anal sex.
Some sexually transmitted infections can spread through the use of unsterilized drug needles, from mother to baby during childbirth, or breast-feeding, and blood transfusions.
Sexually transmitted infections have been around for thousands of years. The genital areas are generally moist and warm environments - ideal for the growth of yeasts, viruses, and bacteria.
Microorganisms that exists on the skin or mucus membranes of the male or female genital area can be transmitted, as can organisms in semen, vaginal secretions, or blood during sexual intercourse.
Examples of sexually transmitted diseases include:
crabs (pubic lice)
human immunodeficiency virus and acquired immunodeficiency syndrome (HIV and AIDS)
human papillomavirus (HPV)
trichomoniasis (parasitic infection)
pelvic inflammatory disease (PID)
Sexually transmitted infections are more easily passed on during unprotected sex - without using safer sex options (i.e., condoms, dams, sanitizing sex toys).
Some infections can be passed on via sexual contact but are not classed as sexually transmitted infections; for instance, meningitis can be passed on via sexual contact, but usually, people become infected for other reasons, so it is not classed as an STD.
The WHO (World Health Organization) estimates that, worldwide, there are more than 1 million new STDs acquired each day. People aged 15-24 acquire half of all new STDs, and 1 in 4 sexually active adolescent females has an STD, such as human papillomavirus or chlamydia. Compared with older adults, individuals aged 15-24 have a higher risk of getting STDs.
However, STI rates among seniors are increasing.
Common sexually transmitted infections
We take a look at some of the most common sexually transmitted infections below.
Also known as chlamydial infection, chlamydia is an STI caused by Chlamydia trachomatis (C. trachomatis), a bacterium that infects humans exclusively. Chlamydia is the most common infectious cause of genital and eye diseases globally - it is also the leading bacterial STI.
According to the CDC (Centers for Disease Control and Prevention), in 2015, nearly 3 percent of girls aged 15-19 had chlamydia.
Women with chlamydia do not usually have signs or symptoms. If there are any, they are usually non-specific and may include:
a change in vaginal discharge
mild lower abdominal pain
If chlamydia is left untreated, it may lead to the following signs and symptoms:
painful sexual intercourse, either intermittently or all the time
bleeding between menstrual periods
You can learn more about chlamydia here.
Chancroid is also known as soft chancre and ulcus molle. It is a bacterial infection caused by fastidious gram-negative streptobacillus Haemophilus ducreyi and is characterized by painful sores on the genitals. It is only spread through sexual contact.
Infection rates are very low in rich countries; it is more common in developing nations, especially among commercial sex workers and some low socioeconomic groups. This is due to the lack of access to healthcare services, the stigma attached to seeking help, a lack of sexual health awareness, and other factors.
In 2015, just 11 cases of chancroid were reported in the United States. Chancroid increases the risk of contracting HIV, and HIV increases the risk of contracting chancroid.
Within 1 day to 2 weeks after becoming infected, the patient develops a bump that turns into an ulcer within a day. The ulcer can be from 1/8 of an inch to 2 inches across, it is very painful, may have well defined, undermined borders, and a yellowish-gray material at its base. If the base is grazed, it will typically bleed. In some cases, the lymph nodes swell and become painful (lymphadenopathy).
Women often have at least four ulcers, while men usually have just one. Males tend to have fewer and less severe symptoms. The ulcers typically appear at the groove at the back of the glans penis (coronal sulcus) in uncircumcised males, or, in females, the labia minora (small inner folds of the vulva) or fourchette (thin fold of skin at the back of the vulva).
Chancroid is treated with a 7-day course of erythromycin, a single oral dose of azithromycin, or a