Sexually transmitted infections, or STIs, are infections that are transmitted through sexual contact and can be viral, bacterial, fungal, or parasitic in nature.
Occasionally you will hear the terms STI and STD (sexually transmitted disease) used interchangeably, but they aren’t exactly the same thing. The difference is small but mighty; infections and diseases are not the same. Infections are curable and go away, while diseases are usually considered to be chronic or ongoing over the course of one’s lifetime. Some (not all) infections that are not treated can evolve into diseases.[1]
Similar to the saying about rectangles and squares (“All squares are rectangles but all rectangles are not squares”), all STDs are STIs, but not all STIs are STDs. Continue reading for specific examples of different types of diagnosis.
Throughout this article, the term STI will include all STIs and STDs.
According to the Centers for Disease Control, sexually transmitted infections are preventable and very common — millions of new infections occur annually in the United States alone. [1]
The number of cases of the three most common sexually transmitted infections (STIs) in the U.S. — chlamydia, gonorrhea, and syphilis — has been rising over the past few decades.
Males account for the majority of cases of gonorrhea and syphilis, while women are more likely to be diagnosed with chlamydia – in fact, the prevalence of chlamydia is consistently higher in females than in males. [2]
The age group of 15 to 24-year-olds is disproportionately affected by STIs. They represent about 50% of all new STI cases annually, even though they make up about 25% of the sexually active population. [2]
The Southern region has the highest rates of reported cases of chlamydia, gonorrhea, and syphilis compared to the other areas. The Western region has also seen significant increases in STI rates, particularly syphilis, over recent years. [2]
In the Midwest, according to Planned Parenthood, cases of STIs increased in 2022 across Nebraska, syphilis cases rose in Native American populations of South Dakota, and STIs increased in some Iowan communities. [3]
Of the eight states with the highest rates of chlamydia per 100,000 population in 2022, seven were Southern states (Louisiana, Mississippi, South Carolina, Georgia, Alabama, North Carolina, and Arkansas). The state with the third highest rate of chlamydia cases was Alaska. [4]
Of the eight states with the highest rates of gonorrhea per 100,000 population in 2022, six were Southern states (Mississippi, Louisiana, Georgia, South Carolina, Alabama, and North Carolina). The states with the second and fourth highest rates of gonorrhea cases were South Dakota and Alaska, respectively. [4]
Trends for syphilis look a bit different — the states with the highest rates of syphilis per 100,000 population in 2022 span across the South, Midwest, Southwest, and West. [4]
How are these infections so common? They are easily transmitted via oral, vaginal, and/or anal sexual contact (depending on the infection).
Furthermore, drug resistance is an obstacle to reducing the prevalence of STIs worldwide – drug resistance occurs when bacterial infections evolve to survive our treatment for them (antibiotics) – it makes infections harder to treat and can lead to more serious health problems. Drug resistance can happen if antibiotics are used too often or incorrectly. [5]
Anyone can get an STI – it’s not, for example, a reflection of someone’s cleanliness – but some factors can increase a person’s risk of contracting an STI. Sometimes, even having one STI puts you at a higher risk of contracting another. [6]
It’s important to keep in mind that the prevalence of STIs in certain communities can indicate larger looming social, cultural, and/or economic factors that can make safer sex practices, STI testing, and treatment more difficult, and even nearly impossible. Any number of the following factors can contribute directly to the prevalence of STIs across many communities, in addition to others:
The social stigmas of certain contraceptive methods, safer sex practices, testing, and treatment can have a huge impact on the prevalence of STIs.
Note: This information is based on the data provided by multiple sources and it should be assumed that “women” refers to individuals assigned female at birth and those with vulvas. “Men” refers to those assigned male at birth and those with penises.
The U.S. Office on Women’s Health announced that north of nine million women in the U.S. receive an STI diagnosis every year and women often experience more serious adverse outcomes than men from STIs. Unfortunately, women also have a higher risk of contracting an STI during unprotected vaginal sex (there’s an even higher risk with unprotected anal sex). [7]
When untreated, chlamydia and gonorrhea increase the risk of chronic pelvic pain and potentially fatal ectopic pregnancies (pregnancies that are not in the uterus, often in the fallopian tubes).
Regarding pregnancy and fertility, STIs can have substantial impacts on a woman’s body and/or pregnancy.
When syphilis is left untreated in pregnant women, it results in the death of the infant up to forty percent of the time, and certain STIs can result in difficulty becoming pregnant and permanent infertility. Additional outcomes of STIs include health complications for fetuses/infants and the mother, further infection, organ damage, certain cancers (like cervical cancer), and even death. [7]
Research shows that women use more healthcare services and spend more on healthcare than men, with the largest spending disparity seen in those between ages 45 and 64. [8]
According to an article published by the World Economic Forum in 2023, an average working American woman spends 18% more on healthcare compared to a man, visits healthcare providers more frequently, and the services she receives are more likely to surpass deductibles. [9]
Frequently, STIs create no symptoms at all or mild symptoms that are easily confused for something else — for example, a urinary tract infection (UTI) or a yeast infection. Getting tested is the only way to be certain.
Read below to learn about the specific symptoms that can arise for some of the most common sexually transmitted infections.
Chlamydia is one of the most common sexually transmitted infections and is bacterial in nature — meaning, it is often easily cured with a course of antibiotics prescribed by a healthcare provider. Most common among people ages 14 to 24, about three million people in America contract chlamydia every year via vaginal, anal, and oral sex. Chlamydia is carried from one person to another via semen, pre-ejaculate (pre-cum), and vaginal fluids and can infect the penis, vagina, cervix, anus, urethra, eyes, and/or throat. However, many people don’t know they have chlamydia. [10]
More than 70% of women with chlamydia won’t present with any symptoms. Still, if or when they do, the most common symptoms are pain while peeing and unusual vaginal discharge. Other symptoms can include pelvic pain, pain during sex (particularly during intercourse), bleeding following sexual activity, and breakthrough bleeding (spotting between periods). [11]
Notably, chlamydia can be spread from a pregnant person to their infant during pregnancy and/or delivery. [12]
Similar to chlamydia, gonorrhea, a.k.a “the clap” or “the drip,” is very common, bacterial, and often easily cured with a course of antibiotics prescribed by a healthcare provider. It’s most common in teenagers and people in their twenties. [13]
Gonorrhea is also carried from one person to another via semen, pre-ejaculate (pre-cum), and vaginal fluids and can infect the penis, vagina, cervix, anus, urethra, throat, and eyes (though it’s rare for eyes). It can be spread from a pregnant person to their infant during pregnancy and/or delivery and can infect your eyes if they come into contact with infected fluids. [13]
Symptoms usually develop within two weeks of infection, but may not appear or be obvious – the NHS estimates that 10% of men and 50% of women will not exhibit symptoms. In women, symptoms may include unusual vaginal discharge, pain or burning while peeing, pelvic pain, breakthrough bleeding, heavier periods than normal, and bleeding after sex. [11]
Herpes, caused by HSV-1 or HSV-2, is viral and causes sores on the genitals or mouth, but doesn’t usually lead to serious health issues. About one in six Americans has herpes. [14]
HIV is a viral infection that attacks the immune system. It is estimated that over one million people in the US live with HIV. It can take a while to develop any signs that you have contracted HIV, but in the first month or so, you may develop flu-like symptoms. [15]
Testing regularly and between partners is an important part of maintaining one’s sexual health, and it can be as easy as at-home testing with Everlywell.
Our at-home lab test screens you from the comfort of your home, and if your results are abnormal or positive, you’ll be able to connect with our independent physician network at no additional cost and may be eligible to receive treatment through services like online STD consults.
Our tests include: