Infections That Harm Sperm: Which Ones Actually Matter

Three matter most: mumps affecting the testicles after puberty, chlamydia or gonorrhoea that has reached the epididymis, and genital tuberculosis, which is under-discussed and may be commoner in India than elsewhere. All three can leave permanent damage. Most of the other infections named on fertility pages either do less than is claimed or have not been shown to do anything measurable.

The honest framing from the guidelines is more cautious than most of what is written about this. The EAU 2025 guideline lists male accessory gland infections — urethritis, prostatitis, orchitis, epididymitis — and records in its own summary of evidence that they are "not clearly associated with impaired natural conception". A systematic review it cites was "unable to draw a strong association between STIs and male infertility due to the limited quality of reported data".

The two things that separate a scare from real harm are whether the infection reached the testis or the ducts, and whether scarring followed. That is what the rest of this page is about.

Almost certainly not on that finding alone. White blood cells in semen mean inflammation, which is not the same thing as infection. The EAU guideline states that leucocytospermia "is not necessarily associated with bacterial or viral infections and therefore cannot be considered a reliable indicator".

It is also a lower bar than it sounds. The threshold is one million white cells per millilitre of semen, and it should be confirmed with a peroxidase stain rather than accepted from a routine count. Bacteria are a separate test: significant bacteriospermia needs more than a thousand colony-forming units per millilitre of a urinary tract pathogen grown from the ejaculate.

On treatment, the guideline is explicit: there is currently no evidence that treating leucocytospermia alone, without evidence of an infective organism, improves conception rates. A 2025 review of asymptomatic leucocytospermia goes further — routine treatment, and particularly empiric antibiotics, is not recommended, because it may disturb the immune balance, promote antibiotic resistance and add cost without demonstrable benefit.

What is worth doing is asking two questions: do I have any symptoms, and has a culture or PCR actually been done. If the answer to both is no, an antibiotic is being given to a number on a page rather than to an infection.

Mumps in a grown man is not the same illness as mumps in a child. Orchitis — inflammation of one or both testicles — is the commonest complication outside the salivary glands, and in young adult men it has been reported in as many as 40 of every 100 mumps cases. It usually appears about a week after the parotid swelling.

Most cases involve one testicle. Both are affected in 10 to 30 of every 100 men with mumps orchitis, and roughly 30 of every 100 post-pubertal men who get mumps orchitis are left subfertile or infertile. Those are the figures a review of the condition draws from the primary reports.

The Indian part of this is specific and checkable: the mumps vaccine is not in India's national immunisation programme, which covers measles and rubella. In a 2023-24 outbreak in Shivamogga, Karnataka, every laboratory-confirmed case among 318 children was unvaccinated for mumps, and the complication rate climbed with age — none of those under five years, 1.9% at five to nine years, and 19.2% at ten years and above (risk ratio 10.1, 95% CI 3.0 to 34.3). Of 508 children tested in Kerala, 78.5% carried mumps antibody against 99.4% for rubella.

What follows for an adult man is limited but real. If you had mumps with testicular pain and swelling after puberty, that belongs in your history, and a semen analysis is a reasonable thing to ask for rather than something to wait for. If you have never had mumps and are not immune, MMR vaccination is a conversation to have with a doctor before conception, not during a pregnancy.

Genitourinary tuberculosis is the second most common form of tuberculosis outside the lungs, and in 5 to 30 of every 100 such cases only the genital organs are involved. There is evidence that genital involvement is commoner in India than in other countries. The epididymis is the organ most often affected.

It is easy to miss because of how it presents. The commonest sign is a painless lump in the scrotum. It typically reactivates decades after the original lung infection — about 30 years on average, with a reported range of 1 to 46 — so there may be no history of tuberculosis to give, and infertility can be the first thing anyone notices. About 10 in every 100 men with genital tuberculosis present with infertility, and tuberculosis is the cause in 4 to 9 of every 100 infertile men diagnosed with obstructive azoospermia.

Treatment is standard anti-tubercular therapy — two months of four drugs, then four months of two. What matters for fertility is that curing the infection does not undo the scarring. Infertility from genital tuberculosis is described as multifactorial and may persist even after successful chemotherapy, obstruction at several points at once is characteristic, and most such cases cannot be reconstructed surgically, so assisted reproduction using surgically retrieved sperm is usually what is left.

One thing to be careful about, because it is widely sold in India. A study of 100 infertile men with unexplained obstructive azoospermia screened them all with a semen tuberculosis PCR. Seven tested positive; four had other clinical evidence of tuberculosis and were treated for six months; none of the four had any improvement in semen parameters. The authors concluded the test found nobody who would have been missed by examination and history, and is not indicated in that situation. Examination first, not the PCR.

This is the distinction that decides everything that follows, and it is not made by a semen culture. An active infection can be treated. Scarring that has already closed the epididymis or the vas cannot be treated with drugs at all.

The things that separate the two are ordinary: an examination of the scrotum for nodules or a thickened vas, testicular volume, FSH, and whether there is any sperm at all in the ejaculate. Azoospermia with normal testicular volume and normal FSH points towards a blockage; azoospermia with small testes and a high FSH points towards a production problem. Those two are managed completely differently.

This is also why the guideline language about antibiotics is worded the way it is. Antibiotics eradicate organisms. They have no effect on inflammatory changes that have already happened and cannot reverse anatomical damage. Clearing an infection is worth doing on its own terms; it is not a fertility treatment.

Pain and swelling in a testicle is the one that should not wait. Sudden severe testicular pain needs same-day assessment, because testicular torsion looks similar and is time-critical. Pain with fever, or pain with discharge or burning on passing urine, needs seeing promptly too.

Acute epididymitis in sexually active men is most often caused by Chlamydia trachomatis, Neisseria gonorrhoeae or Mycoplasma genitalium, and the accompanying urethritis is frequently asymptomatic — which is exactly how these infections reach the epididymis unnoticed. The CDC lists infertility and chronic pain among the complications that treatment aims to avoid, without giving a rate for either.

If a sexually transmitted infection is diagnosed or suspected, the EAU guideline's one Strong recommendation in this area is about your partner, not about you: sexual partners should be referred for evaluation and treatment. Untreated reinfection is how a single episode becomes repeated episodes.

Most of what gets written about infections and sperm sits in this section, including much of what this page used to say.

• It does not establish that infections substantially reduce the chance of a pregnancy. Pooling 35 control-comparator studies, most pregnancy and live birth outcomes did not differ significantly between infected men and non-infected controls.
• It does not establish that infection raises sperm DNA fragmentation. In that same pooled analysis, total motility, vitality and DNA fragmentation index were not significantly different between groups.
• It does not establish that treating leucocytospermia helps. The EAU states there is no evidence that treating it without evidence of an infective organism improves conception rates, and grades the data on antibiotics plus antioxidants for it as insufficient.
• It does not establish a strong link between sexually transmitted infections generally and male infertility. The systematic review the EAU cites was unable to draw one, because of the quality of the available data.
• It does not establish what antiviral or antiretroviral treatment does to sperm. The live version of this page claimed effects for HIV therapy, hepatitis B and Zika that no source retrieved here supports; they have been removed rather than left standing.
• It does not establish that hygiene, diet or sleep protect fertility from infection. Those claims were on this page and are gone.

There is one thing worth saying plainly to anyone reading this after an episode of testicular pain years ago. Whether damage was done is a question a semen analysis and an examination can answer in a fortnight, and not knowing is usually harder than knowing. Sometimes the answer turns out to be testing, timing or a simpler treatment rather than IVF.

• Male infertility after sexually transmitted infections
• Testicular pain and fertility: should you worry?
• How to read your semen analysis report, line by line
• The sperm DNA fragmentation test: is it worth paying for?
• Male reproductive anatomy: where fertility actually fails
• What causes a low sperm count