Written by Fergus Snell. Reviewed by Franseca Steyn, NMC-registered fertility practitioner.
Shaun Greenaway is co-founder of The Male Fertility Hub and is a male fertility coach offering guidance to men dealing with fertility issues.
Can mumps cause infertility? For most men the answer is no, but for a small number it can, and Shaun Greenaway is one of them. His story, recently covered by the BBC, is a clear example of how an illness years earlier can quietly shape a man's fertility long before he ever thinks to check. It is also a reminder that male fertility is rarely on anyone's radar until it suddenly is.
Shaun has since become a male fertility advocate and coach, and we were lucky enough to sit down with him for Men's Health Week. You can read that conversation in our interview on male fertility and mental health. Here, we want to look at the medical side of his journey, and what it tells the rest of us.
What happened to Shaun Greenaway
Shaun and his wife Jenna started trying for a family some years after marrying in 2013. When conceiving did not happen naturally, they sought help. Jenna's tests came back normal. Shaun's showed something he had never expected: there was no sperm in his semen at all, a condition called azoospermia.
The likely cause traced back to a severe bout of mumps in his twenties. Shaun also had a large varicocele, a cluster of enlarged veins in the scrotum that can interfere with sperm production. The couple first tried a procedure to treat the varicocele, then a surgical search for any viable sperm. Neither found what they were hoping for.
After weighing up their options, Shaun and Jenna went down the donor conception route, combining donor sperm with IVF. Their twins, Ray and Evelyn, were born in February 2021. Shaun now spends much of his time supporting other men through similar experiences.
Can mumps cause infertility?
In most cases, mumps does not cause lasting fertility problems. The complication to be aware of is mumps orchitis, painful swelling of one or both testicles that can follow a mumps infection after puberty. According to the NHS, around one in four men who catch mumps after puberty develop orchitis.
Even then, infertility is not the usual outcome. Most men who have orchitis in one testicle see little or no lasting effect on their fertility. The risk rises when both testicles are affected, where studies suggest a meaningful proportion of men can experience a significant drop in sperm production, sometimes severe enough to cause azoospermia.
So the honest answer is that mumps rarely causes infertility, but it can, and Shaun's experience shows what that looks like in practice. It is one of several reasons a past illness is worth mentioning when you think about your fertility, rather than assuming everything is fine.
Azoospermia: what it means when there is no sperm
Azoospermia is the medical term for having no measurable sperm in the ejaculate. It is more common than most people realise, affecting roughly 1 percent of all men and around 10 to 15 percent of men with fertility problems.
There are two broad types. Obstructive azoospermia means sperm are being produced but a blockage stops them reaching the semen. Non-obstructive azoospermia, the more common form, means the testicles are producing little or no sperm in the first place. Causes range from genetics and hormone problems to undescended testes, varicocele, and infections such as mumps orchitis.
Where varicocele fits in
A varicocele, like Shaun's, is one of the more common findings in male fertility assessments. These enlarged scrotal veins can raise the temperature around the testicles and affect sperm production. Many men with a varicocele are perfectly fertile, but in some cases treatment is considered as part of a wider fertility picture. The key point is that none of this is visible or obvious day to day. It only shows up when someone looks.
What this means in practice
The thread running through Shaun's story is timing. Like most men, he had no reason to question his fertility until he and Jenna were already trying for a baby. By then, the causes had been building quietly for years.
That is the norm rather than the exception. Male factors are involved in around half of all fertility difficulties, yet men are still usually tested last. A semen analysis is a simple, low-stress way to replace assumption with information, whether you are actively trying to conceive, planning ahead, or simply curious about your baseline. For more on why this deserves attention, our piece on why we still overlook the 50 percent is a good place to start, alongside our guide to how an at-home sperm test works.
Knowing your numbers does not change what they are. But it does mean that if there is something to understand, you find out on your own terms, with time and support, rather than as a shock midway through trying.
Frequently asked questions
Q: Can mumps cause infertility in men? A: It can, but it usually does not. The risk comes from mumps orchitis, swelling of the testicles after a mumps infection in adulthood. Most men recover fertility, especially if only one testicle is affected. Lasting infertility is more likely when both testicles are involved.
Q: What is azoospermia? A: Azoospermia means there is no measurable sperm in the ejaculate. It affects about 1 percent of men and 10 to 15 percent of men with fertility problems. It can be caused by a blockage, or by reduced sperm production linked to genetics, hormones, varicocele or infection.
Q: Does a varicocele always cause infertility? A: No. Varicoceles are common and many men with one are fully fertile. In some cases they can affect sperm production and may be treated as part of a fertility assessment. The only way to know its impact is through a semen analysis and clinical review.
Q: Should I get a sperm test if I had mumps as an adult? A: It is reasonable to consider. A single semen analysis can confirm whether your sperm health is within normal ranges. If you had mumps orchitis affecting both testicles, or you are planning to try for a baby, testing gives you a clear baseline rather than leaving it to assumption.
If Shaun's story shows anything, it is that fertility can be shaped by things we never connected to it, and that finding out is always better than wondering. If you want to understand your own sperm health, our at-home sperm test with consultation includes lab analysis against WHO reference ranges and results explained one-to-one by an NMC registered fertility nurse, so you are never left to interpret a report alone.
Fergus Snell is co-founder of Malebox Health, an at-home male fertility testing service. With thanks to Shaun Greenaway, male fertility advocate and coach, who shares his story through his peer support work. You can read our full interview with Shaun on male fertility and mental health.
Sources and further reading:
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BBC News, interview with Shaun Greenaway: https://www.bbc.co.uk/news/articles/cx2w4kz7z1ko
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NHS, Mumps: https://www.nhs.uk/conditions/mumps/
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Johns Hopkins Medicine, Azoospermia: https://www.hopkinsmedicine.org/health/conditions-and-diseases/azoospermia
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World Health Organisation, WHO Laboratory Manual for the Examination and Processing of Human Semen, 6th edition.
Malebox Health does not provide medical advice. This article is for informational purposes only. If you have questions about your fertility health, please speak with a qualified healthcare professional.
