Epstein-Barr virus (EBV) is a virus that typically causes a mild to moderate illness. These tests detect antibodies to EBV in the blood and help establish a diagnosis of an EBV infection. Epstein-Barr virus causes an infection that is very common. 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 his life and may reactivate but usually causes few problems unless the person’s immune system is significantly weakened. Sample: Blood (serum) Reference: Negative Frequency: Once a week