References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Infectious mononucleosis — often called mono or glandular fever — is caused by the Epstein-Barr virus (EBV). It’s famously known as “the kissing disease” because it spreads through saliva. It’s not classified as a sexually transmitted infection (STI) because it’s transmitted through many routes besides sex, but it can be passed on during intimate contact including kissing.
Here’s what to know.
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How Mono Spreads
EBV is present in saliva and other body fluids. It spreads through:
- Kissing (the most famous route)
- Sharing drinks, utensils or toothbrushes
- Coughing and sneezing
- Sexual contact involving saliva or genital fluids
- Blood transfusions (rarely)
- Organ transplantation (rarely)
Is It an STI?
Mono is not classified as an STI for a few reasons:
- Most transmission is not sexual
- It spreads easily through non-sexual casual contact
- The majority of people catch it in childhood or adolescence from family members or friends
That said, it can be transmitted through sex, particularly activities involving saliva. If you develop mono after a new sexual partner, it’s reasonable to consider where it came from.
Symptoms
| Symptom | How Common |
|---|---|
| Severe fatigue | Very common |
| Sore throat (often severe) | Common |
| Swollen lymph nodes | Common, particularly in the neck |
| Fever | Common |
| Swollen spleen | Common |
| Swollen tonsils | Common |
| Body aches | Common |
| Rash | Occasional, especially if given amoxicillin |
Symptoms can last weeks to months. The fatigue is often the most frustrating part of recovery.
Mono vs HIV Seroconversion
Mono and HIV seroconversion can look similar — both can cause fever, sore throat, swollen lymph nodes and fatigue. This is why some cases of acute HIV are initially mistaken for glandular fever. If you have mono-like symptoms after a potential HIV exposure, get tested for both.
Diagnosis and Treatment
- Diagnosis — usually by blood test for EBV antibodies or monospot test
- Treatment — no specific antiviral; rest, fluids and paracetamol
- Avoid contact sports and heavy exercise — until your spleen has returned to normal size
- Antibiotics — don’t help mono and can cause a rash with amoxicillin
Recovery
Most people feel better within a few weeks, though some take months to fully recover. The fatigue can be particularly persistent. Once you’ve had mono, you develop long-term immunity and usually don’t get it again.
Read more: Seroconversion symptoms | Swollen lymph nodes and HIV | What is HIV?
Frequently Asked Questions
Is glandular fever the same as mono?
Yes. They’re two names for the same condition, caused by the Epstein-Barr virus.
Can I catch mono from casual kissing?
Yes, any exchange of saliva can transmit EBV if you haven’t already been exposed. Most adults are already immune from childhood or teenage exposure.
Does mono affect fertility?
No. Mono doesn’t affect fertility or reproductive health.
Related reading
- Blood Test for Syphilis, Hepatitis B and Hepatitis C
- Can You Get an STI From Being Fingered?
- Can You Catch an STI From a Toilet Seat?
- Can You Clear HPV Once You Have It?
- Can You Die From Hepatitis B?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
