As a reproductive endocrinologist, I see countless patients who walk through my doors with quiet stories of loss—sometimes the loss of hope, sometimes the loss of time. But every year, there’s a particular group of gentlemen who share a strikingly similar history.

They come from different countries. Many grew up in regions where the measles-mumps-rubella (MMR) vaccine was unavailable or inconsistently administered. They had mumps as children, recovered, and thought nothing more of it.

Fast-forward 15 or 20 years, and they are now adults yearning for fatherhood. Only then do they discover that their childhood mumps infection left an indelible mark: azoospermia—the complete absence of sperm in their semen.

It’s for them, and for those who may be at risk, that I’m writing this piece. Because although we don’t talk about it much anymore in the era of vaccines, mumps orchitis remains a cause of acquired male infertility worldwide.

What is mumps orchitis?

Mumps orchitis is inflammation of one or both testicles caused by the mumps virus, a single-stranded RNA virus from the Paramyxoviridae family. It typically occurs 4–10 days after the classic parotid gland swelling, but in about 10 percent of cases, it appears in isolation without parotitis.

It primarily affects post-pubertal males, with the highest incidence between 15 and 29 years of age. Historically, before widespread vaccination, 15–30 percent of post-pubertal males with mumps developed orchitis, with 60–70 percent unilateral and up to 40 percent bilateral.

How does it damage fertility?

The virus spreads from the respiratory tract, enters the bloodstream, and localizes in the testicular tissue. Inside the testes, it infects the seminiferous tubules and interstitial cells, triggering:

• Immune-mediated inflammation and edema
• Increased intra-testicular pressure leading to ischemia and necrosis
• A cytokine surge that disrupts the blood–testis barrier
• In some bilateral cases, anti-sperm antibodies and autoimmune infertility

This inflammatory cascade permanently damages the germinal epithelium responsible for sperm production. Interestingly, Leydig cells (testosterone-producing cells) are relatively spared, so testosterone levels are often normal even when sperm production fails.

What are the long-term outcomes?

The severity of fertility damage depends on whether orchitis is unilateral or bilateral:

• Unilateral orchitis: Usually does not cause sterility but can temporarily or mildly reduce sperm quality.
• Bilateral orchitis: Carries a 30–87 percent risk of infertility, often due to severe oligozoospermia or azoospermia.

Testicular atrophy occurs in 30–50 percent of affected testes, contributing significantly to impaired spermatogenesis.

Treatment and prevention

There’s no antiviral treatment. Management is supportive—NSAIDs for pain, scrotal support, and rest. The true game-changer is vaccination. Two doses of the MMR vaccine confer 88–95 percent protection.

Unfortunately, in areas without robust vaccination programs, boys remain vulnerable. Many of the patients I see in my clinic come from regions where mumps was endemic during their childhood. They are often devastated to learn that the infection they had at age eight silently impacted their future family-building dreams.

Can assisted reproduction help?

Yes. For men with azoospermia from mumps orchitis, assisted reproductive technology offers hope.

Sperm retrieval rates with micro‑dissection testicular sperm extraction are remarkably high—75–85 percent, much better than idiopathic non-obstructive azoospermia.

Once sperm is retrieved, intracytoplasmic sperm injection yields fertilization rates of approximately 78 percent and pregnancy rates of approximately 85 percent, with live birth rates around 66 percent, comparable to other causes of infertility.

This means that even after bilateral orchitis, many men can still achieve biological fatherhood through advanced reproductive techniques.

Why am I sharing this?

Because these cases keep happening.

Each year, I meet a handful of men who never knew their childhood mumps infection could cost them their fertility. They often come to me only after years of unexplained infertility. By the time they arrive, they’re not just dealing with azoospermia—they’re grappling with guilt, confusion, and the feeling that no one warned them.

I want to shed light on this forgotten complication for two reasons:

• To alert physicians and patients in under-vaccinated populations that mumps orchitis is not just an old textbook diagnosis—it’s still very real.
• To offer hope to those already affected. Modern reproductive medicine can often retrieve sperm and help achieve pregnancy.

The bigger picture

In many ways, mumps orchitis is a public health success story—vaccination reduced its burden dramatically. But it’s also a reminder that vaccines prevent more than acute illness; they safeguard futures.

For clinicians, it’s important to recognize that in men with unexplained azoospermia, especially those from countries with limited vaccine access, mumps orchitis should remain on the differential. Early counseling and referral to a reproductive urologist can make all the difference.

For patients, the message is simple: protect your children. Vaccinate. And if you’ve had mumps in adolescence or adulthood and are planning a family, consider a fertility evaluation early.

Because no one should have to find out too late that a childhood infection closed the door to fatherhood.

Oluyemisi (Yemi) Famuyiwa is a renowned fertility specialist and founder, Montgomery Fertility Center, committed to guiding individuals and couples on their path to parenthood with personalized care. With a background in obstetrics and gynecology from Georgetown University Hospital and reproductive endocrinology and infertility from the National Institutes of Health, she offers cutting-edge treatments like IVF and genetic testing. She can be reached on Linktr.ee, LinkedIn, YouTube, Facebook, Instagram @montgomeryfertility, and X @MontgomeryF_C.