Is glandular fever (mononucleosis) an STI?

No. Glandular fever isn’t listed as a sexually transmitted infection by the NHS or the World Health Organization. In the US, it’s known as infectious mononucleosis, or mono.

But the virus that usually causes it can be passed on during sex. Glandular fever mainly spreads through spit, and US health experts say the Epstein-Barr virus (EBV) can also spread through blood and semen during sexual contact.

Glandular fever is a viral infection that mostly affects teenagers and young adults. It’s usually caused by EBV, one of the most common viruses in the world. Most people catch EBV at some point, often in childhood, without any symptoms.

Glandular fever gets better without treatment, but it can make you feel very ill for weeks.

Glandular fever spreads through contact with the spit of someone who has it, for example by:

• kissing
• sharing cups, cutlery or other utensils
• being around someone who’s coughing or sneezing
• touching your mouth, eyes or nose with hands or objects that have the virus on them

You can be infectious for up to 7 weeks before you get symptoms, and for several months after you’ve been unwell. EBV also stays in your body after you’ve had it, and it can become active again and be passed on to others, even years later.

The NHS lists these symptoms of glandular fever:

• a high temperature
• swollen glands, which may be in the neck, head, armpits, elbows or groin
• a sore throat
• a rash, which may be harder to see on black or brown skin
• a headache
• tiredness

Most people start to feel better within 2 to 4 weeks. For some people, tiredness can last for several months.

Some people get a short flu-like illness 2 to 6 weeks after catching HIV, with a sore throat, a high temperature, swollen glands, tiredness and a rash. That can look a lot like glandular fever.

UK HIV testing guidelines recommend an HIV test for anyone with a glandular fever-like illness. If you’ve had sex without a condom, it’s worth getting tested, even if you think your symptoms are glandular fever. Read more in “HIV testing urged in those with glandular fever symptoms”

If you think you’ve been exposed to HIV in the last 72 hours, get urgent medical advice about PEP, a medicine that can stop you getting infected.

A doctor can often tell from your symptoms, and may do a blood test to check for EBV. There’s no vaccine, and antibiotics won’t help, because glandular fever is caused by a virus. The NHS advises:

• resting
• drinking plenty of fluids
• taking painkillers such as paracetamol or ibuprofen
• avoiding strenuous activities, such as heavy lifting or sport

Glandular fever can make your spleen swell, and sometimes it can burst, which is why sport and heavy lifting are best avoided. To avoid passing glandular fever on, the NHS advises washing your hands regularly, not kissing others, not sharing cups or cutlery, and not giving blood.

Call 999 if you can’t swallow, including your own spit, have severe difficulty breathing, or have severe stomach pain.

Get urgent medical care if swallowing is difficult and painful, or you’re more short of breath than usual. See a doctor if you have a very high temperature, a severe sore throat, swollen glands, extreme tiredness or a sore throat that isn’t getting better.

Better2Know offers:

• HIV 4th Generation: a blood test for HIV from 28 days after sex, with results in 1 day.
• Full Screen: tests for 7 infections, including HIV, Hepatitis B, Syphilis, Chlamydia and Gonorrhoea, from 28 days after sex, with results in 3 days (5 days for the home test).
• Epstein-Barr Virus: a blood test for antibodies to EBV at one of our clinics, with results in 2 days.

If you test before 45 days, a negative HIV result needs a repeat test. A Syphilis test in the first 3 months after sex can miss the infection, so you may need a repeat test. Not sure which test you need? Our Patient Care Team is available 24/7 on 020 7099 0955.

Is glandular fever the same as EBV?

Not quite. EBV is the virus that usually causes glandular fever, but many people catch EBV without ever getting glandular fever. US health experts say at least 1 in 4 teenagers and young adults who catch EBV develop it.

Can I go to work or school with glandular fever?

Yes, as soon as you start to feel better. UK health protection guidance says people with glandular fever don’t need to stay away from school or other settings.

Can glandular fever cause long-term problems?

Most people get better with no problems. Sometimes it can lead to complications, such as long-term tiredness, liver problems or a burst spleen.

Glandular fever isn’t an STI. It mainly spreads through spit, although the virus that causes it can also be passed on during sex. Most people feel better within a few weeks. Because the symptoms can look like early HIV, it’s worth getting an HIV test if you’ve had sex without a condom.

Book an HIV test at a clinic near you or order a home test kit. Our Patient Care Team is available 24/7 on 020 7099 0955.

Not in the UK? Choose your country from the selector at the top of the page for local tests and prices.

This article was last updated on 1 October 2026.

Medical review. This article was medically reviewed by Dr Steve Chapman, Doctor with a wealth of clinical experience in the field of STIs, on 3 February 2026. It is general information and not a substitute for personal medical advice.

Sources

1. NHS, Glandular fever, reviewed 20 December 2023. https://www.nhs.uk/conditions/glandular-fever/
2. UK Health Security Agency, A to Z of infectious diseases in children and young people’s settings, updated 7 September 2026. https://www.gov.uk/government/publications/health-protection-in-schools-and-other-childcare-facilities/a-to-z-of-infectious-diseases-in-children-and-young-peoples-settings
3. UK Health Security Agency, Public health exclusion periods in children and young people’s settings, updated 7 September 2026. https://www.gov.uk/government/publications/health-protection-in-schools-and-other-childcare-facilities/public-health-exclusion-periods-in-children-and-young-peoples-settings
4. US Centers for Disease Control and Prevention, About Epstein-Barr virus (EBV), 9 May 2024. https://www.cdc.gov/epstein-barr/about/index.html
5. US Centers for Disease Control and Prevention, About infectious mononucleosis (mono), 9 May 2024. https://www.cdc.gov/epstein-barr/about/mononucleosis.html
6. NHS, HIV and AIDS, reviewed 9 July 2025. https://www.nhs.uk/conditions/hiv-and-aids/
7. NHS, Sexually transmitted infections (STIs), reviewed 13 May 2024. https://www.nhs.uk/conditions/sexually-transmitted-infections-stis/
8. World Health Organization, Sexually transmitted infections (STIs), 10 September 2025. https://www.who.int/news-room/fact-sheets/detail/sexually-transmitted-infections-(stis)
9. British HIV Association, British Association for Sexual Health and HIV and British Infection Association, Adult HIV testing guidelines, 2020. https://bhiva.org/wp-content/uploads/2024/10/HIV-testing-guidelines-2020.pdf
10. British Association for Sexual Health and HIV, UK guidelines for the management of syphilis, 2024. https://bashh.org/_userfiles/pages/files/syphilis_2024.pdf