Sexually Transmitted Infections: Facts and Statistics You Need to Know

According to statistics from the Department of Health and Human Services (HHS), the rate of sexually transmitted infections (STIs) in the United States reached an all-time high among people of any sex and of all races or ethnicities in 2018.1

The common STIs—chlamydia, gonorrhea, and syphilis—accounted for more than 2.4 million of these new infections, a 34% increase from 2013, when 1.8 million cases were reported. Half of new infections are among youth.1

This article takes a closer look at the eight most common STIs in the United States, including the rate of infection and the groups at greatest risk of infection. It also explains how these STIs are spread and the current recommendations for testing and screening.

STI Overview

Sexually transmitted infections, formerly known as and sometimes still referred to as sexually transmitted diseases (STDs), are a group of bacterial, viral, and parasitic diseases spread primarily through sexual contact.

In the United States, the eight most common STIs (by order of annual new infections) are:

• Human papillomavirus (HPV)
• Trichomoniasis
• Chlamydia
• Gonorrhea
• Genital herpes
  
• Syphilis
• Human immunodeficiency virus (HIV)
  
• Hepatitis B

Of the eight, chlamydia, gonorrhea, syphilis, and trichomoniasis are curable. The others are not and either need to be managed with medications or, in the case of HPV, routinely monitored to avoid complications like cancer.

The risk of all STIs can be greatly reduced by practicing safer sex. This includes the consistent use of condoms and a reduction in the number of sex partners. Even so, condoms and other forms of barrier protection are not infallible and may be more effective with some STIs than with others.

How STIs Are Transmitted

STIs vary in how they are transmitted (passed) from one person to the next,

Some STIs are efficiently passed through all forms of sexual contact, including oral, vaginal, or anal sex. Others, like hepatitis B and HIV, are unlikely to be passed through oral sex. Others still can be passed through intimate skin-to-skin contact.

Some STIs can also be transmitted through nonsexual routes, such as from mother to child (MTCT) during pregnancy, childbirth, or breastfeeding. The shared use of needles, syringes, and other drug paraphernalia is another common transmission route for several viral STIs.

How Common Are STIs?

It may surprise you to know that in 2018 1 in 5 people in the United States—or roughly 68 million—was living with an STI. On top of that, there were over 26 million new infections, according to the Centers for Disease Control and Prevention (CDC),

Because some STIs can be cured and others can't, their prevalence (meaning the number of people currently living with a disease) and incidence (the number of people newly infected) can vary.

In short, curable STIs like chlamydia and gonorrhea generally have a higher incidence, while incurable ones like HIV and genital herpes have a higher prevalence as the number of cases accumulates year on year.

Here is the prevalence and incidence rates of the top eight STIs in the United States, as reported in 2018.

STIs by Race/Ethnicity

There are disparities in the rates of STIs among different populations in the United States. Black and Latinx people have higher rates of STI infections compared to White people and also tend to have lower rates of diagnosis and treatment.

There are numerous reasons for this, not least of which include higher rates of poverty, poorer access to quality sexual health services, and a general distrust of public health services. Adding to the burden, high rates of STIs in communities of color increase the odds of infection simply because more people are infected.

These dynamics translate to disproportionately higher rates of STIs among Black people in the United States, particularly when compared to White people. According to the CDC, the reported rates of cases of these conditions were:

• Chlamydia: Black females 5 times more than White females; Black males 6.8 times more than White males
• Gonorrhea: Black Americans 7.7 times more than White Americans; Black males 8.5 times more than White males; Black females 6.9 times more than White females
  
• Syphilis: Black Americans 4.7 times more than White Americans
  
• HIV: Black Americans 1.7 times more than White Americans
• HIV deaths from the disease: Black Americans with HIV 6.5 times more than White Americans with HIV

The picture is little improved among Latinx people. According to CDC statistics, the reported rates of cases of these conditions were:

• Chlamydia: Latinx Americans 1.9 times more than White Americans
• Gonorrhea: Latinx Americans 1.6 times more than White Americans; Latinx females 1.4 times more than White female; Latinx males 1.8 times more than White males
• Syphilis: Latinx Americans 2.2 times more than White Americans
• HIV: Latinx Americans 1.2 times more than White Americans

STIs by Age and Gender

Age, sex, and sexual orientation can all contribute to a person's chance of being exposed to and contracting STIs in different ways. Being younger, female, or a man who has sex with men increases the odds of getting one or more of these communicable infections.

Younger People

Younger age contributes to the risk of STIs simply because a person is more likely to be sexually active. As a result, almost half of the 26 million new STI cases reported in 2018 were among people age 15 to 24. The cost to the U.S. healthcare system is enormous, logging in annually at over $4 billion for this age group alone.

Female Sex

Females have a greater chance of getting STIs for several reasons, including that the vaginal lining is thinner, more porous, and more delicate than the skin on a penis. Symptoms of many STIs are also often missed because they can mimic other conditions, such as yeast infection or urinary tract infection.

When compared to heterosexual males:

• Females are 1.5 times more likely to get HPV.
• Females are 1.7 times more likely to get chlamydia.
• Females are 1.8 times more likely to get genital herpes.
• Females are 2.3 times more likely to get HIV.
• Females are 2.8 times more likely to get gonorrhea.
• Females are 4.6 times more likely to get trichomoniasis.

Only with syphilis are heterosexual males 4.1 times more likely to be infected than females. The rate of HBV between males and females is more or less equal.

Men Who Have Sex With Men (MSM)

STIs disproportionately affect men who have sex with men. As a group, MSM tend to have more sex partners than heterosexuals and engage in sexual practices (such as anal sex) that are highly efficient in passing HIV, syphilis, and other STIs.

Syphilis is also of particular concern, given that MSM are nearly 11 times more likely to be infected than heterosexual males. In turn, syphilis can increase the odds of getting HIV by compromising body tissues that allow the virus easier access into the body. The same is true with STIs such as gonorrhea and chlamydia.

Causes of STIs and Risk Factors

STIs are caused by bacteria, viruses, or parasites that thrive in body fluids such as semen, vaginal fluids, anal secretions, blood, and breast milk. Their presence in these fluids doesn't necessarily mean that they can establish an infection; the risk varies by the STI type, the route of transmission, the level of exposure, and other factors.

Even so, there are commonalities in how these STIs are passed and the risk factors that consistently increase the likelihood of infection. These include:

• Engaging in condomless sex
• Having multiple sex partners
• Having a history of STIs
• Having an untreated STI
• Engaging in "rough" sex (which can damage tissues)
• Using alcohol or recreational drugs (which can impair judgment)
• Sexual assault

What Are the Mortality Rates for STIs?

Death is rare with trichomoniasis, genital herpes, and bacterial STIs like chlamydia, gonorrhea, or syphilis. However, certain viral STIs like hepatitis B, HIV, and HPV can lead to death if left untreated or unmonitored.

Hepatitis B and HIV are both incurable, but there are medications that can slow the progression of the disease and reduce the risk of complications. While there are no treatments for HPV, regular Pap smears can check for any abnormal changes in cells that might lead to cervical cancer.

Of these three STIs, the risk of death varies by the disease type:

• Hepatitis B can cause liver complications like cirrhosis (liver scarring) and liver cancer in some people. Compared to the general population, people with chronic hepatitis B have a sixteenfold increased risk of liver-related death.
• HIV causes the progressive loss of immune function that can leave you vulnerable to a host of serious opportunistic infections. If left untreated, HIV is inevitably fatal with a median survival time of eight to 10 years from the time of infection.
• HPV can cause cervical cancer and other cancers if infected with certain high-risk strains. If cervical cancer does occur, the median five-year survival rate is roughly 67% and the median age of death is 59 years, according to the National Cancer Institute.

Screening and Early Detection

Generally speaking, the early detection of an STI ensures earlier treatment and affords better outcomes. It can also help prevent the spread of disease to others.

With that said, the recommended screening of common STIs can vary. Routine screening is not recommended for certain STIs, like genital herpes or HPV in men, either because it won't change outcomes or it won't prevent the spread of infection.

The CDC currently advises screening for the following groups.

Other groups (such as people with HIV, transgender men or women, pregnant people, or individuals at high risk of infection) may have different, specific, or more frequent screening recommendations not listed here.

Summary

The rate of sexually transmitted infections (STIs) is on the rise in the United States among people of any sex and of all races and ethnicities. Today, no fewer than 1 in 5 people are living with an STI, while more than 26 million are newly infected with either a curable or incurable STI.

Women, Black Americans, and men who have sex with men have a greater chance of getting STIs for different reasons. Younger age is also a factor, given that nearly half of all new infections occur in people between 15 and 24 years of age.

The CDC recommends routine screening for people at risk of chlamydia, gonorrhea, syphilis, and HIV. The consistent use of condoms and a reduction in the number of sex partners can help lower the risk of infection.