Epstein-Barr virus (EBV) is a virus that typically causes a mild to moderate illness. Blood tests for Epstein-Barr virus detect antibodies to EBV in the blood and help establish a diagnosis of EBV infection.
Epstein-Barr virus causes an infection that is very common. According to the Centers for Disease Control and Prevention (CDC), most people in the United States are infected by EBV at some point in their lives. The virus is very contagious and easily passed from person to person. It is present in the saliva of infected individuals and can be spread through close contact such as kissing and through sharing utensils or cups.
After initial exposure to EBV, there is a period of several weeks before associated symptoms may appear, called the incubation period. During the acute primary infection, the virus multiplies in number. This is followed by a decrease in viral numbers and resolution of symptoms, but the virus never completely goes away. Latent EBV remains in the person's body for the rest of that person's life and may reactivate but usually causes few problems unless the person's immune system is significantly weakened.
Most people are infected by EBV in childhood and experience few or no symptoms. However, when the initial infection occurs in adolescence, it can cause infectious mononucleosis, commonly called mono, a condition associated with fatigue, fever, sore throat, swollen lymph nodes, an enlarged spleen, and sometimes an enlarged liver. These symptoms occur in about 25% of infected teens and young adults and usually resolve within a month or two.
People with mono are typically diagnosed by their symptoms and the findings from a complete blood count (CBC) and a mono test (which tests for a heterophile antibody). About 25% of those with mono do not produce heterophile antibodies and will have a negative mono test; this is especially true with children. Tests for EBV antibodies can be used to determine whether or not the symptoms these people are experiencing are due to a current infection with the EBV virus.
EBV is the most common cause of mono. According to the CDC, examples of other causes of mono include cytomegalovirus (CMV), hepatitis A, hepatitis B or hepatitis C, rubella, and toxoplasmosis. Sometimes, it can be important to distinguish EBV from these other illnesses. For instance, it may be important to diagnose the cause of symptoms of a viral illness in a pregnant woman. Testing can help to distinguish a primary EBV infection, which has not been shown to affect a developing baby, from a CMV, herpes simplex virus, or toxoplasmosis infection, as these illnesses can cause complications during the pregnancy and may harm the fetus.
It can also be important to rule out EBV infection and to look for other causes of the symptoms. Those with strep throat, an infection caused by group A streptococcus, for instance, need to be identified and treated with antibiotics. A person may have strep throat instead of mono or may have both conditions at the same time.
Several tests for different types and classes of EBV antibodies are available. The antibodies are proteins produced by the body in an immune response to several different Epstein-Barr virus antigens. During a primary EBV infection, the level of each of these EBV antibodies rises and falls at various times as the infection progresses. Measurement of these antibodies in the blood can aid in diagnosis and typically provides the healthcare practitioner with information about the stage of infection and whether it is a current, recent, or past infection.