Sexually transmitted infections (STIs) reached record levels across Europe in 2024, according to data released in May 2026 by the European Centre for Disease Prevention and Control (ECDC). The increase was driven by sharp rises in gonorrhea and syphilis, alongside persistent gaps in testing, prevention, and access to care.

The agency warned that urgent, targeted action is needed to curb transmission and prevent long term consequences, including infertility.

Gonorrhea cases reached 106,331 in 2024, a 303% increase compared with that in 2015. Syphilis cases rose to 45,577, more than double the number reported a decade earlier. Chlamydia is the most commonly reported STI, with 213,443 cases. Lymphogranuloma venereum also continued to see ongoing transmission, with 3490 reported cases.

“Sexually transmitted infections have been on the rise for 10 years and reached record high levels in 2024. Untreated, these infections can cause severe complications, such as chronic pain and infertility and, in the case of syphilis, problems with the heart or nervous system. Most distressingly, between 2023 and 2024, we have seen a near doubling of congenital syphilis, where infections pass directly to newborns, leading to potentially lifelong complications,” said Bruno Ciancio, head of the ECDC Unit, Directly Transmitted and Vaccine-Preventable Diseases in a press release. “Protecting your sexual health remains straightforward. Use condoms with new or multiple partners, and get tested if you have symptoms, such as pain, discharge or an ulcer.”

Over the past decade, cases of congenital syphilis increased by 243%.

Transmission trends vary significantly across different population groups. Men who have sex with men remain the most disproportionately affected group, with the steepest long-term increases in gonorrhea and syphilis. Among heterosexual populations, syphilis is rising, particularly among women of reproductive age, the consequences of which are a near doubling of congenital syphilis cases.

Female Fertility

More than 1 million STIs are acquired worldwide each day, and many remain undiagnosed, according to Ángela Llaneza, MD, a gynecologist specializing in reproductive medicine, gynecologic endocrinology, and regenerative gynecology and scientific director of Tambre Fertility Clinics.

Speaking with El Médico Interactivo, part of the Medscape Professional Network, she said“Many go unnoticed, yet they are responsible for a substantial proportion of fertility problems diagnosed years later.”

A study published in Scientific Reports examined the global burden of female infertility attributable to chlamydia, gonorrhea, and maternal sepsis. Worldwide, infertility cases increased from 11.2 million in 1991 to 19.1 million in 2021. The researchers projected that infertility associated with STIs will continue to increase through 2025.

“Their impact stems from their ability to cause pelvic inflammatory disease (PID), damage to the fallopian tubes, and pregnancy complications when they are not detected and treated promptly,” Llaneza said.

Both Neisseria gonorrhoeae and Chlamydia trachomatis infections can ascend through the reproductive tract and cause PID. Available evidence suggests that approximately 25% of PID cases lead to infertility due to damage to the fallopian tubes (tubal infertility), according to scientific evidence.

One of the major challenges is that these infections are mostly asymptomatic or cause only mild, nonspecific symptoms.

“This lack of warning signs delays diagnosis and increases the risk of fertility complications,” Llaneza said.

Beyond chlamydia and gonorrhea, emerging evidence suggests that other disturbances of the genital microbiome may also affect female fertility.

A study conducted at Monash University reignited debate about bacterial vaginosis, which affects approximately one third of women and has traditionally been viewed as an imbalance of the vaginal microbiota rather than an STI.

The result of the study suggested that bacterial vaginosis may, in fact, be sexually transmitted and that treating only the female partner may be insufficient to prevent recurrence. Recurrence occurred in 35% of couples when both partners received treatment compared with 63% when only the woman was treated.

Male Fertility Effects

STIs can also affect fertility in men.

“Conditions such as gonorrhea and chlamydia can cause epididymitis or obstruction of the seminal ducts, leading to reduced sperm counts or even complete absence of sperm in the ejaculate,” Llaneza said.

Even in the absence of obstruction, some infections can affect critical semen parameters, including sperm motility, morphology, and DNA integrity.

“These abnormalities can impair fertilizing capacity and embryo quality, even when conventional semen analysis results fall within normal ranges,” she added.

A recent review of infertility and urologic disorders in men concluded that male infertility is a multifactorial condition in which urological causes play a major and often treatable role.

The review examined conditions including varicocele, obstructive azoospermia, erectile dysfunction, and Peyronie disease and emphasized the importance of systematic urologic evaluation in men presenting with fertility concerns.

The authors advocated for a multidisciplinary approach integrating urology, endocrinology, reproductive medicine, nutritional counseling, and psychological support to address both biologic and psychosocial aspects of male infertility.

Early Diagnosis and Treatment

International organizations, including the World Health Organization and the ECDC, have intensified warnings in recent years about the consequences of rising STI rates.

The sustained rise in infections, coupled with growing rates of maternal and congenital syphilis, has reinforced the need for earlier diagnosis, prompt treatment, and preventive strategies, particularly among women of reproductive age.

Most STIs can be treated successfully if identified early. Timely diagnosis, appropriate treatment, and follow-up testing to confirm eradication can prevent long-term damage to the reproductive system.

What Physicians See in Practice

“In clinical practice, one of the most common mistakes is underestimating mild infections or assuming that the absence of symptoms means there is no risk,” Llaneza said.

“A simple screening test performed during a gynecological examination can make the difference between preserving fertility and compromising it in the long term.”

For patients who have already experienced reproductive damage, assisted reproductive technologies may offer options.

In vitro fertilization can bypass irreversible tubal obstruction in women, whereas surgical sperm retrieval combined with intracytoplasmic sperm injection can achieve high rates of reproductive success in men with severe impairment of sperm production or transport.

A Preventable Cause of Infertility

“STIs pose a real but often underestimated threat to reproductive health,” Llaneza said.

“The difference today lies not only in treatment but also in diagnosing infections before the damage becomes irreversible. Prevention, screening, and early consultation remain the most effective tools for protecting fertility. In many cases, the key is not providing more treatment but intervening in time.”

In April 2026, the Spanish Society of Infectious Diseases and Clinical Microbiology updated its consensus document on the diagnosis and treatment of STIs in adults, children, and adolescents. The Spanish Ministry of Health adopted the document as a reference resource for clinicians.

The Spanish Ministry of Health also provides physicians with guidance through Sexually Transmitted Infections: Diagnosis, Treatment, Prevention, and Control, along with a position statement on the prophylactic use of doxycycline for STI prevention.

This article was translated from El Médico Interactivo on Univadis.