Epstein-Barr virus protein and DNA. Molecular model of the DNA-binding domain of a viral protein (green) bound to a lytic gene promoter element (viral strand of DNA, right). The viral protein is the Epstein-Barr virus (EBV) transcription factor ZEBRA (Zta, Z, EB1), also known as BZLF1 trans-activator protein. EBV is a herpesvirus (it is also called human herpesvirus 4 or HHV-4). It is the cause of glandular fever (also called infectious mononucleosis). The DNA strand is viral DNA that forms during the lytic phase of the virus life cycle, where the viral DNA exists within the host cell separately from the host cell's DNA (deoxyribonucleic acid).