STIs are on the rise: What you need to know

By Naveed Saleh, MD, MS, for MDLinx
Published August 8, 2019

Key Takeaways

Once considered a death sentence, HIV was the most feared sexually transmitted infection (STI) at one point in time. With the advent of pre-exposure prophylaxis treatment and effective antiretroviral therapy, however, it appears that we now have a firm grip on the lethal virus.

Unfortunately, there’s still some bad news for sexually active Americans. Although HIV/AIDS-related deaths have been reduced by more than 50% since peak rates in 2004, STI rates are continuing to rapidly rise in the United States.

In fact, according to the CDC, about 2.3 million cases of chlamydia, gonorrhea, and syphilis were diagnosed among Americans in 2017. This number eclipsed the previous record set in 2016—by more 200,000 cases—and marks the fourth year in consecutive increases. These older diseases have long predated our battle with HIV—gonorrhea was even mentioned in the Bible—but still manage to scare the public and health community alike.

Let’s take a look at five scary STIs that are still prevalent or on the rise in the United States.

Genital herpes

  • Pathogen: Herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2).
  • Prevalence: 776,000 Americans have genital herpes.
  • Trends: While the rate of herpes infection has decreased in recent years, about 50% of teens and adults aged < 50 years are infected with the oral herpes virus, and approximately 1 in 8 Americans have an infection with the genital herpes virus.
  • Diagnostic tests: Detection of HSV on polymerase chain reaction (PCR) or isolation on viral culture.
  • Transmission: Contact with herpes virus lesion infections, mucosal surfaces, genital secretions, or oral secretions.
  • Treatment: No cure, but antivirals can prevent or shorten the length of outbreaks; daily treatment with antivirals can minimize the risk of transmission.
  • Prevention: Proper use of condoms.

What to know about genital herpes: Herpes is itchy, painful, and seemingly ubiquitous. Furthermore, there is a stigma associated with the disease that can make interaction with a sexual partner embarrassing or shameful.

Herpes lesions can spread to the buttocks, groin, thigh, finger, or eye, and HSV can increase the risk of being infected with HIV. In pregnant women, herpes infection can be spread to the baby at the time of delivery, as it passes through the birth canal, thus causing damage to the nervous system, mental retardation, or death.

The first herpes outbreak is typically of longer duration and exhibits increased viral shedding, which makes HSV transmission more likely. Furthermore, these initial lesions are accompanied by systemic symptoms, including fever, body aches, headache, and swollen lymph nodes. Subsequent outbreaks can present with prodromal symptoms—including genital pain and shooting pains in the legs, hips, or buttocks—but no systemic symptoms.

Fortunately, symptomatic recurrent outbreaks may decrease over time. Moreover, recurrences and subclinical shedding are much less common with genital HSV-1 vs genital HSV-2 infection.

Human papilloma virus

  • Pathogen: Human papilloma virus (HPV).
  • Prevalence: 79 million Americans have HPV.
  • Trends: A total of 43,371 new cases of HPV-associated cancers were documented in 2015. Between 1999 and 2015, cervical carcinoma rates dropped by 1.6% per year, and oropharyngeal squamous cell carcinoma (SCC) rates went up 2.7% per year among men and 0.8% per year among women. In 2015, there were 11,788 reported cases of cervical carcinoma and 18,917 cases of oropharyngeal SCC (men: 15,479, women: 3,438).
  • Diagnostic tests: HPV tests on cervical cancer screens (ie, Pap screens).
  • Transmission: Skin-to-skin contact, but not exchange of body fluids.
  • Treatment: Antivirals are not used to treat lesions.
  • Prevention: HPV vaccines are available; proper use of condoms.

What to know about HPV: Although most HPV infections are self-limited, asymptomatic or unrecognized severe presentations can occur—with cancer sequelae especially disquieting. Infections with oncogenic, high-risk strains, such as HPV 16 and 18, are the cause for most cervical, penile, vulvar, vaginal, anal, and oropharyngeal cancers and precancers. Furthermore, non-oncogenic, low-risk HPV strains, such as HPV 6 and 11, can lead to genital and anogenital warts and, more rarely, recurrent respiratory papillomatosis, which refers to the development of benign lesions in the respiratory tract.


  • Pathogen: Treponema pallidum bacterium.
  • Incidence: In 2017, there were 101,567 reported new diagnoses of syphilis (all stages).
  • Trends: In 2017, there were 30,644 cases of primary and secondary syphilis reported in the United States, equaling a rate of 9.5 cases per 100,000 population. This rate follows a 10.5% increase vs 2016 when there were 8.6 cases per 100,000 population, and a 72.7% increase vs 2013 when there were 5.5 cases per 100,000 population.
    Syphilis outbreaks among the general population are on the rise. For instance, through October 22, 2018, the Alaska Department of Health and Social Service reported the highest incidence of syphilis in the past 40 years, with 75 cases seen in adults aged 18-75 years (55 in men who have sex with men). Arizona has also been experiencing a syphilis outbreak. Since January 2015, the monthly average of female syphilis cases has increased 253%, from 19 to 67 cases per month. Unlike in Alaska, most new syphilis cases in Arizona occur among women and babies, per the Arizona Department of Health Services.
  • Diagnostic tests: Blood tests with both nontreponemal tests and treponemal tests are needed to confirm. Nontreponemal tests are nonspecific and used for screening, whereas treponemal tests can detect antibodies.
  • Transmission: Contact with a syphilitic sore (ie, chancre).
  • Treatment: Benzathine penicillin G administered intramuscularly.
  • Prevention: Proper use of condoms.

What to know about syphilis: If left untreated, syphilis can become progressively worse. The primary stage of syphilis is marked by chancres. The secondary stage is characterized by rashes, fever, swollen lymph glands, sore throat, patchy hair loss, headaches, weight loss, muscle aches, and fatigue. Tertiary syphilis impacts various organ systems, including the brain, nerves, eyes, heart, blood vessels, liver, bones, and joints. Moreover, neurosyphilis and ocular syphilis can occur at any stage, thus leading to serious damage of the central nervous system. Of note, syphilis can lie dormant for long periods of time during the latent stage.

Syphilis can be transferred from mother to baby, which can result in either stillbirth or developmental delay, seizures, and eventual death. Lastly, the presence of lesions can increase the risk of HIV infection.

Although long common in developing countries, syphilis has re-emerged in industrialized countries. Moreover, syphilis resistance to azithromycin—a macrolide recommended as second-line treatment—has been reported in a number of cases.


  • Pathogen: Neisseria gonorrhoeae bacterium.
  • Incidence: Approximately 820,000 new gonococcal infections occur each year in the United States.
  • Trends: Between 2016 and 2017, the rate of reported gonorrhea cases went up 18.6%, and increased 75.2% ever since a historic low in 2009.
    Gonorrhea outbreaks in the general population are on the rise, with increased incidence particularly in small communities. For instance, in Rock Island County, IL, which has 143,000 residents, there were 44 cases of gonorrhea in the first 3 months of 2019. During the same time period in 2018, there were 27 cases.
  • Transmission: Sexual contact with the penis, vagina, anus, or mouth; ejaculation not necessary to transmit infection.
  • Diagnostic tests: Testing urine, urethra (men), endocervical, or vaginal specimens with nucleic acid amplification testing (NAAT); gonorrhea culture can also be used to test endocervical or urethral swab specimens; and swabs can be taken from the pharynx, based on a history of oral sex, or from the anus, based on a history of anal intercourse.
  • Treatment: A single dose of 250 mg of intramuscular ceftriaxone in combination with 1 g of oral azithromycin; gonorrhea often co-occurs with chlamydia, which is why these infections are co-treated.
  • Prevention: Proper use of condoms.

What to know about gonorrhea: You may have heard of “super gonorrhea,” which was first described in the United Kingdom in March 2018, when a case of gonorrhea that was resistant to azithromycin and ceftriaxone was detected.

According to the CDC: “Gonorrhea has progressively developed resistance to the antibiotic drugs prescribed to treat it. Following the spread of gonococcal fluoroquinolone resistance, the cephalosporin antibiotics have been the foundation of recommended treatment for gonorrhea. The emergence of cephalosporin-resistant gonorrhea would significantly complicate the ability of providers to treat gonorrhea successfully, since we have few antibiotic options left that are simple, well-studied, well-tolerated and highly effective. It is critical to continuously monitor antibiotic resistance in Neisseria gonorrhoeae and encourage research and development of new treatment regimens.”

Most men and women with gonorrhea are asymptomatic. Signs and symptoms in men include dysuria and urethral discharge. Urethral infection can also be accompanied by epididymities, with testicular and scrotal pain. Although rare, epididymitis can lead to infertility in men.

In women, symptoms are usually mild and can be confused with a bladder or vaginal infection. They include dysuria, vaginal discharge, and bleeding between periods. More seriously, untreated gonorrhea can spread to the fallopian tubes and uterus resulting in pelvic inflammatory disease (PID)—which can result in abdominal pain, fever, internal abscesses, and chronic pelvic pain. It can also damage the fallopian tubes, leading to infertility or ectopic pregnancy.

Symptoms of rectal infection in men or women include discharge, itching, soreness, bleeding, or painful bowel movements. Although usually asymptomatic, pharyngeal infection results in sore throat. The presence of gonorrhea can increase risk for HIV infection.

Lastly, untreated cases of gonorrhea can spread to the blood and cause life-threatening disseminated gonococcal infection, which involves arthritis, tenosynovitis, and dermatitis.


  • Pathogen: Chlamydia trachomatis bacterium.
  • Incidence: 1,708,569 cases of chlamydia were reported in 2017.
  • Trends: In 2017, a rate of 528.8 cases per 100,000 population was reported. Between 2016 and 2017, the rate went up 6.9%, from 494.7 to 528.8 cases per 100,000 population. Being the most common STI, outbreaks of chlamydia among the general public have been on the rise. In Denver, CO, for example, there has been a 24% increase during the past 4 years, with 7,317 residents, or more than 1 in 100 people affected.
  • Transmission: Sexual contact with the penis, vagina, mouth, or anus of an infected partner, with or without ejaculation.
  • Diagnostic tests: NAATs are the most sensitive tests and the gold standard for diagnosis. Specimens can be obtained via vaginal swabs or urine. Cell cultures can also be used to diagnose.
  • Treatment: Dual therapy to cover for gonorrhea.
  • Prevention: Proper use of condoms.

What to know about chlamydia: Chlamydia is a really big problem among young women in the United States. The CDC recommends annual chlamydia screening for sexually active women younger than age 25, as well as women age 25 and older who may be at increased risk for infection (eg, new or multiple partners).

Although usually asymptomatic, untreated infection in women can lead to PID. Furthermore, infection with chlamydia can facilitate HIV infection. Pregnant women who are infected can pass the infection to their infants during delivery, thus resulting in ophthalmia neonatorum, which can cause infant blindness and pneumonia.

Mycoplasma genitalium

We’ve looked at five STIs of particular concern in the United States (and worldwide). Now, let’s look at an up-and-coming STI that is also worrying public health officials.

  • Pathogen: Mycoplasma genitalium bacterium.
  • Prevalence: Unknown. In one meta-analysis, researchers estimated that 1.3% of individuals in developed countries are affected and, in developing countries, 3.9%.
  • Transmission: Sexual contact.
  • Diagnostic tests: Multiplex NAAT (not FDA-approved for testing for M. genitalium); slow growth on culture makes it difficult to detect.
  • Treatment: Syndromic therapy.
  • Prevention: Proper use of condoms.

What to know about M. genitalium: We still don’t know a lot about this STI. But we do know that antibiotic resistance in M. genitalium is already an issue. M. genitalium was first discovered in the early 1980s in men with non-gonococcal urethritis, but epidemiologists didn’t begin analyzing it until the 1990s with the advent of PCR.

Researchers have shown that M. genitalium is present in a large proportion of men with urethritis and in women with cervicitis, thus routine testing has been suggested by some, even among the low-risk general population.

It’s unknown whether this infection can cause male infertility or male anogenital tract disease syndromes, but, in women, it can cause cervicitis and is linked to PID, infertility, and preterm birth. Symptoms of infection with M. genitalum appear to be similar to infection with chlamydia.

Because there is no recommended way to test for M. genitalium, the CDC recommends a generalized strategy of doxycycline and azithromycin. However, this is problematic because neither of those two antibiotics is very effective against M. genitalium. Doxycycline works only 30% to 40% of the time, and azithromycin works on average about 60% of the time. It's not clear why doxycycline doesn’t work well, but the mediocre efficacy of azithromycin is due to antibiotic resistance.

Importantly, M. genitalium lacks a cell wall, so beta-lactams—including penicillins and cephalosporins—won’t work against it. Moxifloxacin has appeared effective in treating patients with previous failures, but this approach needs to be proven in clinical trials.

Let’s talk about sex

Despite sex being prominent in the media, many physicians view sexual issues among patients as too personal and too difficult to discuss. Consequently, STI counseling in the primary care clinic is rarely performed, or deficient when it is done. Because many physicians may feel inadequately trained to take a sexual history, here are a few tips to approach this conversation with your patients without any awkwardness: How to talk to patients about their sexual history.

Share with emailShare to FacebookShare to LinkedInShare to Twitter