Sexually transmitted infections (STIs) are common and highly contagious. They spread predominantly by unprotected sexual contact, including vaginal, anal and oral sex. Some STIs can also be transmitted from mother-to-child during pregnancy, childbirth and breastfeeding. There are several types of STIs, some have distinctive symptoms, but some are asymptomatic, meaning you may not know you have it unless you do a test.
How common are STIs?
STIs are very common, particularly among younger people, with over 1 million new cases daily worldwide.1 Most infections show no symptoms, meaning you can unknowingly have and transmit an STI if sexually active. According to the Centers for Disease Control (CDC), about 20 million new cases of STIs are reported each year in the United States, with approximately 10 million occurring in individuals aged 15 to 24.2 Globally, there are an estimated 374 million new infections annually with 1 of the 4 curable STIs: chlamydia, gonorrhoea, syphilis, and trichomoniasis.3
What causes STIs?
STIs develop when bacteria, viruses or parasites enter your body through sexual contact. These microorganisms are present in bodily fluids such as blood, urine, semen and saliva. STIs can be transmitted through various sexual activities, including vaginal, oral and anal sex. It's important to note that penetrative sex is not necessary to contract an STI. Certain STIs, such as herpes and human papillomavirus (HPV), can be spread through skin-to-skin contact, even without sexual penetration.
What are the symptoms?
When present, common symptoms of STIs include:
- an unusual discharge from the vagina, penis or anus
- pain when peeing
- lumps or skin growths around the genitals or bottom (anus)
- a rash
- unusual vaginal bleeding
- itchy genitals or anus