Glandular fever is a viral infection caused by the Epstein-Barr virus (EBV), best known for producing a combination of fever, severe sore throat, and swollen lymph nodes that can leave you exhausted for weeks. It’s also called infectious mononucleosis, or simply “mono.” About 9 out of 10 adults carry antibodies to EBV, meaning most people encounter the virus at some point in their lives.
How You Catch It
EBV spreads primarily through saliva, which is why glandular fever is sometimes called “the kissing disease.” You can also pick it up by sharing drinks, utensils, or toothbrushes with someone who carries the virus. Once the virus enters your body, it targets a specific type of white blood cell called B lymphocytes, latching onto receptors on their surface and establishing a lifelong, usually dormant, infection inside them.
The incubation period is long compared to most infections. Symptoms typically appear four to six weeks after you’re exposed to the virus, which makes it difficult to pinpoint exactly where you caught it. People can also shed the virus in their saliva for months after recovering, and many carriers spread it without ever knowing they were infected.
The Classic Symptoms
The hallmark of glandular fever is a triad: fever, a painful sore throat (pharyngitis), and swollen lymph nodes, particularly in the neck and armpits. The sore throat is often severe enough that swallowing becomes genuinely difficult, and the tonsils can become visibly red and swollen, sometimes with white patches that look a lot like strep throat.
Beyond the classic three, you may also notice:
- Profound fatigue that feels far worse than ordinary tiredness
- Headache and body aches
- A swollen spleen or liver, which can cause discomfort under the left or right side of your ribs
- A faint rash, especially if you’re given certain antibiotics (like amoxicillin) while infected
- Tiny red or purple spots (petechiae) on the roof of your mouth
The acute phase usually resolves within about two weeks, and most people recover fully in two to four weeks. However, the fatigue can linger for months after other symptoms have cleared.
How It Differs From Strep Throat
Because both glandular fever and strep throat cause a sore throat, swollen tonsils, and even petechiae on the palate, they’re easy to confuse. A few features point more strongly toward glandular fever: lymph nodes swollen in the armpits (not just the front of the neck), noticeable fatigue and body aches, and a swollen spleen. Strep throat, on the other hand, tends to come on faster, may produce a rough, sandpaper-like rash on the body (scarlet fever), and gives the tongue a distinctive “strawberry” appearance. Symptoms like cough, runny nose, and hoarseness are uncommon with strep and suggest a viral cause instead.
How Glandular Fever Is Diagnosed
Doctors often suspect glandular fever based on your symptoms and a physical exam, but blood tests confirm it. The most common first step is a rapid test called the Monospot, which detects a type of antibody your immune system produces in response to the infection. It’s quick and inexpensive, with about 87% sensitivity and 91% specificity, meaning it catches most cases but can occasionally give a false negative, especially in the first week of illness or in young children.
If the Monospot comes back negative but glandular fever is still suspected, a more specific blood test can look for antibodies directed against EBV itself. These EBV-specific antibody tests are more accurate, with around 97% sensitivity and 94% specificity. A standard blood count will also typically show an elevated number of white blood cells with an unusual appearance, which further supports the diagnosis.
Treatment and Recovery
There is no antiviral medication that treats glandular fever. Because EBV is a virus, antibiotics won’t help, and taking certain antibiotics like amoxicillin during the infection frequently triggers a widespread rash. Treatment focuses entirely on managing symptoms: rest, fluids, over-the-counter pain relief for the sore throat and fever, and patience.
In rare cases where swollen tonsils or lymph nodes become severe enough to threaten the airway, or when the infection triggers complications like a dangerous drop in platelet count or destruction of red blood cells, doctors may prescribe a short course of corticosteroids to reduce swelling. This is uncommon and reserved for genuinely serious situations.
Most people feel significantly better within two to four weeks, but full recovery, especially the fatigue, follows its own timeline. Pushing yourself back to normal activity too quickly often backfires. Listening to your body during recovery matters more than hitting a specific date on the calendar.
The Spleen and Physical Activity
One of the most important practical concerns with glandular fever is the spleen. The infection commonly causes the spleen to enlarge, and an enlarged spleen is vulnerable to rupture, particularly from a direct blow to the abdomen or intense physical strain. A systematic review of reported cases found that splenic rupture occurred an average of 14 days after symptoms began, with cases documented up to 8 weeks later. Men under 30 within the first four weeks of illness appear to be at highest risk.
The majority of spleen injuries happen within the first 21 days and become exceedingly rare after 28 days. Most guidelines recommend resting for at least three weeks, then gradually returning to light activity once fever, fatigue, and sore throat have resolved. Avoidance of contact sports, heavy lifting, and vigorous exercise for a full eight weeks is a common and cautious recommendation. Your doctor may use imaging to confirm the spleen has returned to normal size before clearing you for full activity.
Long-Term Fatigue
For most people, glandular fever is a miserable few weeks followed by a slow but steady return to normal. For a smaller group, fatigue persists well beyond the acute illness. A prospective study tracking patients after viral infections found that 12% of participants still experienced disabling fatigue, muscle pain, cognitive difficulties, and mood disturbance six months after infection. About 11% of the total group met the diagnostic criteria for chronic fatigue syndrome at that point.
This post-viral fatigue doesn’t mean the virus is still actively replicating. Rather, it reflects an immune and nervous system response that takes longer to settle. There’s no reliable way to predict who will develop prolonged symptoms, though pushing too hard during the initial recovery phase is generally thought to increase the risk. If fatigue persists for more than a few months and is interfering with daily life, it’s worth discussing with a doctor, as targeted approaches to managing energy levels and sleep quality can help.
Who Gets Glandular Fever
Glandular fever is most common in teenagers and young adults, typically between the ages of 15 and 24. This isn’t because the virus only circulates in that age group. In many parts of the world, children are exposed to EBV early in life and experience either mild symptoms or none at all. When first exposure is delayed until adolescence or adulthood, the immune response tends to be more dramatic, producing the full-blown illness.
You can only get glandular fever once in the classic sense. After the initial infection, the virus remains dormant in your body for life, but your immune system keeps it in check. Reactivation can occur, particularly during periods of immune suppression, but it rarely produces the same illness again.