 Therefore, these tests are useful for diagnosing infectious mononucleosis in people with highly suggestive symptoms and a negative heterophile antibody test.About 10% of people who present a clinical picture of infectious mononucleosis do not have an acute Epstein–Barr-virus infection.A differential diagnosis of acute infectious mononucleosis needs to take into consideration acute cytomegalovirus infection and "Toxoplasma gondii" infections.