Epstein-Barr virus (EBV) is one of the most common viruses found in people. At some point in your life, you've probably been infected with EBV. There are several different tests your doctor may use to diagnose EBV and the diseases it causes. EBV testing can tell if you're susceptible to EBV or if you've had a past or recent infection.
When Do You Need to Have an Epstein-Barr Virus Test?
The Epstein-Barr virus causes infectious mononucleosis and other illnesses. It's spread primarily through saliva by kissing or sharing food and utensils. Many people are infected with EBV as children and don't have any symptoms. Mononucleosis occurs mostly in teens and adults.
You don't normally need to have an EBV antibody test to diagnose infectious mononucleosis. You may need a test if you don't have a typical case of mononucleosis or if your doctor thinks you may have another illness caused by EBV infection.
You may also need to get tested if you have the symptoms of mononucleosis but a negative test, or if you're pregnant and have flu-like symptoms. If you’ve been exposed to someone with mononucleosis but don't have any symptoms, you may need a test. It's possible your doctor may need to do a test to check your immune system function.
What Is Being Tested?
The Epstein-Barr virus test checks your blood for antibodies. After you are first exposed to EBV, there is an incubation period of several weeks before you start to have symptoms. After the incubation period, the virus multiplies, and you may have symptoms. After this period, which is called the acute primary infection, the virus will decrease in number. If you had symptoms, they'll go away.
EBV never completely goes away. It's always in your body and may reactivate. It doesn't usually cause any problems, but it may if your immune system is weak.
What Are the Epstein-Barr Virus Tests?
An antigen is a substance that your immune system doesn't recognize. Your immune system makes antibodies in response to antigens to fight them. Your doctor can check for antibodies to the following EBV antigens in your blood:
Viral Capsid Antigen (VCA). There are two antibodies that your body makes in response to VCA. These are anti-VCA IgM and anti-VCA IgG. Anti-VCA IgM appears when you're first infected with EBV and usually disappears in 4 to 6 weeks. Anti-VCA IgG first appears in the acute infection phase, peaks 2 to 4 weeks after infection, and then declines but stays with you for the rest of your life.
Early antigen (EA). Anti-EA IgG first shows up in the acute phase of your infection. After 3 to 6 months, anti-EA levels may become undetectable. But up to 20% of people have antibodies to EA for years.
EBV nuclear antigen (EBNA). You develop antibodies to EBNA 2 to 4 months after infection, and they last for the rest of your life. They are not present during the acute phase of infection.
Monospot test. This is also called the heterophile antibody test. The CDC does not recommend this test for diagnosing mononucleosis. It isn't reliable in children under 5 because they may not produce the antibody. It can produce false positives and false negatives. There are also other conditions that produce heterophile antibodies besides EBV.
But this test is often used because it's quick and inexpensive. The Infectious Diseases Society of America still recommends using it. Positive and negative Monospot tests should be followed up with other antibody tests.
What Do the Results Mean?
The antibody tests show one of three results:
Susceptible to infection. If you don't have antibodies to the VCA you're considered susceptible to infection.
Primary infection. You have a new or recent EBV infection if you have anti-VCA IgM but you don't have antibodies to EBNA. You may also have a primary infection if you have a high or rising level of anti-VCA IgG but no antibody to EBNA after 4 weeks of infection. In some rare cases, people with an active EBV infection don't make antibodies to EBV antigens.
Past infection. If you have antibodies to both VCA and EBNA, it means you've had an infection in the past. It could have been months or years ago. Most adults have these antibodies, because over 90% of adults have been infected with EBV at some point. You may have high levels of antibodies for years, so this doesn't mean you have an active infection.