What causes mononucleosis-like syndrome?

Mononucleosis-like syndrome is caused by viruses other than Epstein-Barr virus (EBV), with cytomegalovirus (CMV) being the most common culprit. While classic mononucleosis results from EBV infection, CMV and other viruses like toxoplasma and human herpesvirus-6 can produce identical symptoms. These viruses infect white blood cells and lymphatic tissue, triggering the characteristic fatigue, fever, sore throat, and swollen lymph nodes that define the syndrome.

What is the best test for mononucleosis-like syndrome?

The Cytomegalovirus (CMV) Antibodies, IgM, Quantitative test is the most important test for mononucleosis-like syndrome because it detects active CMV infection, the leading non-EBV cause of these symptoms. This blood test measures IgM antibodies that appear during recent or active CMV infection, helping differentiate CMV mononucleosis from EBV mononucleosis when standard mono tests are negative. Your healthcare provider may also order EBV antibody testing and a complete blood count (CBC) to rule out other causes and assess your immune response.

When should I get tested for mononucleosis-like syndrome?

You should get tested if you experience persistent fatigue, fever, sore throat, and swollen lymph nodes lasting more than a week, especially if a standard mononucleosis test comes back negative. Testing is particularly important if you have extreme exhaustion that interferes with daily activities, enlarged spleen causing abdominal discomfort, or if you are pregnant or immunocompromised, as CMV infection requires different monitoring. Early diagnosis helps your healthcare provider create an appropriate management plan and rule out other serious conditions.

What are the symptoms of mononucleosis-like syndrome?

Mononucleosis-like syndrome causes extreme fatigue, high fever, severe sore throat, and swollen lymph nodes in the neck and armpits. You might also experience headaches, muscle aches, loss of appetite, and an enlarged spleen that causes abdominal tenderness. Some people develop a skin rash or notice their symptoms lasting longer than typical viral infections, with fatigue persisting for weeks or months even after other symptoms resolve.

Who is at risk for mononucleosis-like syndrome?

Young adults and teenagers are most commonly affected by mononucleosis-like syndrome, though anyone can develop it at any age. People with weakened immune systems, including organ transplant recipients and those undergoing chemotherapy, face higher risk of severe CMV infection. Healthcare workers, daycare employees, and parents of young children also have increased exposure to CMV since the virus spreads through saliva, urine, and other body fluids.

What happens if mononucleosis-like syndrome is left untreated?

Untreated mononucleosis-like syndrome typically resolves on its own in healthy individuals, but complications can develop in some cases. The infection can cause spleen enlargement leading to rupture if you engage in contact sports or strenuous activity, which is a medical emergency. In immunocompromised individuals, untreated CMV infection can lead to serious complications affecting the eyes, lungs, liver, and digestive system, making proper diagnosis and monitoring essential for at-risk populations.

Can mononucleosis-like syndrome be diagnosed with a blood test?

Yes, mononucleosis-like syndrome is diagnosed with blood tests that detect specific viral antibodies and assess your immune response. The CMV IgM antibody test identifies recent or active cytomegalovirus infection, while a complete blood count (CBC) shows characteristic changes in white blood cells. Your doctor may also order liver function tests since CMV can affect the liver, and additional viral antibody panels help rule out other infections causing similar symptoms.

How is mononucleosis-like syndrome treated?

Mononucleosis-like syndrome is treated primarily with rest, hydration, and supportive care since antibiotics do not work against viral infections. You should avoid strenuous activities and contact sports for at least three to four weeks to prevent spleen rupture, and over-the-counter pain relievers help manage fever and throat pain. Immunocompromised patients may require antiviral medications like ganciclovir or valganciclovir to control CMV infection, and your healthcare provider will monitor liver function and blood counts throughout recovery.

How can I prevent mononucleosis-like syndrome?

You can prevent mononucleosis-like syndrome by practicing good hygiene, including frequent handwashing and avoiding sharing drinks, utensils, or personal items with others. Since CMV spreads through saliva and body fluids, avoid kissing or close contact with people who have active infections. Pregnant women and immunocompromised individuals should be especially careful around young children, who often carry CMV without symptoms, and healthcare workers should follow proper infection control protocols.

What can I do at home for mononucleosis-like syndrome?

At home, prioritize rest and sleep to help your immune system fight the infection, and drink plenty of water, herbal teas, and warm broths to stay hydrated. Gargle with warm salt water to soothe your sore throat, and use a humidifier to ease breathing and throat discomfort. Eat nutritious foods when you have an appetite, avoid alcohol to protect your liver, and refrain from heavy lifting or contact sports until your doctor confirms your spleen has returned to normal size.

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Mononucleosis-like Syndrome Test

Mononucleosis-like Syndrome Blood Test

What is Mononucleosis-like Syndrome?

Mononucleosis-like syndrome is a collection of symptoms including fatigue, fever, sore throat, and swollen lymph nodes that resemble classic infectious mononucleosis. It is caused by viruses other than Epstein-Barr virus (EBV), most commonly cytomegalovirus (CMV), which produces identical symptoms. The Cytomegalovirus (CMV) Antibodies, IgM, Quantitative test is the most important test for diagnosis when symptoms suggest mononucleosis but EBV testing is negative.

Written by Private MD Labs Medical Team

Last updated: December 30, 2025

Getting your blood test with us is easy, private & backed by the power of science.

Long story short:

In the test options, use the filters or search box to narrow your choices and find the test you want.
If you need a hand navigating through options, text our super friendly support team at 754-799-7833, and we'll provide tailored suggestions to help you find the ideal test.
Once your order is placed, we’ll create your doctor’s lab order remotely, without any need for you to make a trip to a doctor in person or to talk to the doctor. Expect to receive your doctor’s lab order right in your inbox. It will also be in your patient portal if you need to find it later. We’ll also include instructions regarding fasting and other requirements for your test. Your patient portal will be auto-created hassle-free during checkout.
If this is your first time ordering, you'll be prompted to create a password for instant login access to your patient portal. It's a quick way to conveniently access your orders and results whenever you want.
When you’re ready, visit one of our 4,000 locations. Just bring your ID – no printing or faxing of your lab order is needed, as your order and details will already be in the lab system.
Note that most lab locations don’t accept walk-ins, so it’s best to book an appointment in advance. Don’t worry – we’ll provide detailed instructions along the way.
You’ll get your results via email & SMS and dive into understanding your body better. Yup, that easy!

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