What Are the Symptoms of Mono?

Mononucleosis is caused by a virus

Patient Being Examined by Doctor
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Infectious mononucleosis, mono for short, is a condition usually caused by the Epstein-Barr virus (EBV) or, less commonly, cytomegalovirus (CMV). Mono is sometimes called "kissing disease" because it is spread through saliva and close contact. Symptoms usually develop four to six weeks after you are exposed to the virus.

About 95 percent of the adult population has been infected with EBV, but it doesn't always lead to symptoms, especially when people become infected as children.

It only causes mono 35 percent to 50 percent of the time, and these cases are usually in teenagers and young adults. One in four teens who are exposed to the virus will develop infectious mononucleosis. For this reason, age is an important factor in diagnosing mono.

Symptoms of Mono

Mono may include some or all of the following symptoms which may appear at different times during the course of the illness:

  • Fatigue (usually extreme)
  • Fever of 100 to 103 F (gets worse at night)
  • Sore throat
  • Swollen lymph glands in the neck and armpits
  • Swollen tonsils that may or may not have white patches on them
  • Swollen liver or spleen (rare)
  • Abdominal pain
  • Headache
  • Jaundice
  • Rash
  • Decreased appetite

The severity of symptoms varies greatly between individuals. When young children become infected with mononucleosis, (which is rare), their symptoms may be more subtle and may include poor feeding and irritability. In rare cases, symptoms may become severe enough to require hospitalization.

Because the symptoms of mono can closely resemble strep throat—which needs to be treated with antibiotics—it is important to see a doctor. You should go to the emergency room if you cannot swallow or have a high fever that you cannot control. In very rare cases, mono can cause heart problems, so get immediate medical attention if you have chest pain, difficulty breathing, or any other cardiovascular symptoms.

Contact your doctor with any other worrisome or unexplained symptoms of mono.

How is Mono Diagnosed?

Your doctor will usually perform a thorough exam before ordering blood work or prescribing treatment. He will be looking for swollen lymph nodes in the neck and swollen tonsils, which may be covered in white or yellow patches. In severe cases, the doctor may be able to feel an enlarged liver or spleen when pushing on your belly.

If the doctor suspects mono, he may order blood work which will usually reveal a higher than normal amount of white blood cells (cells that fight off infection). Mono is usually diagnosed by your symptoms or by testing your antibody levels to EBV or CMV. 

Treatment for Mono

The symptoms of mono can last quite a while, with an average being one to two months. You should start to feel better after about 10 days, though it can take as long as three months to fully recover. Since the illness is caused by a virus, treatment is aimed at managing the symptoms. There is no cure or vaccine for mono.

Supportive care for mono includes doing these things:

  • Get plenty of rest, at least eight hours per night.
  • Drink plenty of non-caffeinated fluids and avoid alcoholic beverages as your liver may be inflamed.
  • Over-the-counter medications such as acetaminophen and ibuprofen are useful in reducing a fever and treating sore throat pain. Consult your doctor or pharmacist before combining over-the-counter medications with prescription medications.
  • To manage sore throat pain, you may also try to gargle with warm salt water to ease the pain of a sore throat or suck on a cough drop or other throat lozenge. Cold fluids also help to reduce pain and swelling in the back of the throat.
  • Achy muscles can be treated using over-the-counter muscle ointments, such as Icy Hot, or by using hot pads. A warm bath may also be beneficial in easing aches and pains.
  • Avoid contact sports until you are fully recovered as you will have an enlarged spleen and it could rupture. Mild exercises such as walking or swimming are allowed as long as you are not fatigued.

Prognosis and Complications of Mono

The virus never goes away but becomes dormant. It may become active again, but people rarely experience mono twice. Once you're infected, this virus will stay in your blood for the rest of your life, although you won't always be contagious. The virus goes through periods where it is active and contagious, and long stretches of time where the virus remains dormant. Even if the virus is active, you usually won't feel sick, so it's impossible to know when you are contagious (making the potential of infecting others unavoidable).

Some people can develop chronic fatigue from the Epstein-Barr Virus. Your doctor may suspect chronic fatigue syndrome if your symptoms of mono go on longer than four months. Mono is practically never fatal. The virus has been implicated in nasopharyngeal cancer and Burkitt's lymphoma, but these cancers are rare.