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, and sometimes by genital contact - the infection can be passed on via vaginal intercourse, oral sex, and anal sex.
Some sexually transmitted infections can spread through the use of unsterilized IV drug needles, from mother to baby during childbirth or breastfeeding, and blood transfusions.
Sexually transmitted infections have been around for thousands of years.
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.
Common types of STI/STD
The term "venereal disease" is much less used today, while "sexually transmitted diseases" is slowly giving way to "sexually transmitted infections", because the last term has a broader range of meaning - a person can pass on the infection without having a disease (they do not have to be ill to infect other people).
The genital areas are generally moist and warm environments - ideal for the proliferation of yeasts, viruses and bacteria.
Examples of sexually transmitted infections (STIs) include:
- Crabs (Pubic Lice)
- Genital herpes
- Genital warts
- Hepatitis B
- Human Papillomavirus (HPV)
- Trichomoniasis (parasitic infection)
- Molluscum Contagiosum
- Pelvic Inflammatory Disease (PID)
- Syphilis, gonorrhea
- Trichomoniasis (Trich)
- Yeast infections
Sexually transmitted infections are more easily passed on during unprotected sex - without using a condom.
Some infections can be passed on via sexual contact, but are not classed as sexually transmitted infections, because sexual contact is not the primary vector for the pathogens that cause the infections - an example is meningitis, it can be passed on via sexual contact, but usually people become infected for other reasons.
The WHO (World Health Organization) estimated over ten years ago that over 1 million people each day became infected with a sexually transmitted infection - most experts believe the figure is considerably higher today. The majority of these new infections occur in young adults aged up to 25 years, while approximately one third occur among individuals younger than 20 years of age. Globally, girls aged 14 to 19 are almost twice as susceptible to STIs than boys of the same age.
Common sexually transmitted infections
We take a look at some of the most common sexually transmitted infections below.
There are nearly 3 million reported cases of Chlamydia in the US each year (American Sexual Health Association).
Also known as chamydial 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), 6.8% of girls aged 14 to 19 years have Chlamydia today.
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 the Chlamydia is left untreated, it may lead to the following signs and symptoms
- Pelvic pain
- Painful sexual intercourse, either intermittently or all the time
- Bleeding between menstrual periods
You can learn more about chlamydia here.
Also known as soft chancre and ulcus molle. A bacterial infection caused by fastidious Gram-negative streptobacillus Haemophilus ducreyi, and is characterized by painful sores on the genitalia. It is spread solely 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.
The average prevalence in the US, UK, Australia, France and Canada is approximately 1 case in every 2 million people. It is a risk factor for contracting HIV, due to their shared-risk exposure; also, one infection facilitates the transmission of the other
Within one day to two 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 in to 2 inches across, it is very painful, may have well defined, undermined borders, has a yellowish-gray material at its base. If the base is grazed it will typically bleed. In about 30% to 60% of 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 the labia minora or fourchette in females.
Chancroid is treated with a seven day course of Erythromycin, a single oral 1 gram dose of Azithromycin, or a single IM dose of Ceftriaxone.
3) Crabs (Pubic Lice)
Pthiriasis (pubic lice manifestations) are primarily spread through sexual contact. Pets do not play any part in the transmission of human lice. The lice attach to the pubic hair, and may also be sometimes found in the armpits, moustache, beard, eyelashes, and eyebrows. They feed on human blood.
The vernacular "crabs" comes from the appearance of the lice, with their crab-like claws and body shape.
4) Genital herpes
This STI is caused by the herpes simples virus (HSV). The virus affects the skin, cervix, genitals, and some other parts of the body. There are two types:
- HSVp1, also known as Herpes Type 1
- HSV-2, also known as Herpes Type 2.
Herpes is a long-term (chronic) condition. A significant number of infected individuals never show any symptoms and do not know about their herpes status.
HSV is easily transmissible from human-to-human - by direct contact. Most commonly, transmission occurs through vaginal, oral or anal sex. In most cases, the virus remains dormant after entering a human being.
The signs and symptoms associated with genital herpes, if they do appear, may include:
- Blisters and ulceration on the cervix
- Vaginal discharge
- Pain on urinating
- Generally feeling unwell (malaise)
- Cold sores around the mouth
- Red blisters - these can be painful, especially after they burst and leave ulcers on the external genital area, rectum, thighs and buttocks.
You can learn more about genital herpes here.
On the next page we look at other common sexually transmitted infections including Hepatitis B, HIV/AIDS, Human Papillomavirus, Trichomoniasis, Scabies, Syphilis, Gonorrhea and more. On the final page we look at the best ways to prevent getting a sexually transmitted infection.