Based on the analysis of foreign and domestic literature, the article presents the features of infectious mononucleosis caused by the main pathogens from the Herpesviridae family, course of the disease at various phases of the infectious process. The article identifies clinical and laboratory manifestations characteristic of each pathogen. The authors discuss the issues related to the lack of the unified terminology for describing chronic herpes virus infection. The article discusses the causes of persistent herpes virus infections, risk factors for the adverse course and outcome of herpes virus infections.

Objective. To assess the association between clinical and laboratory characteristics of infectious mononucleosis (IM) and disease etiology and phase of infection. Patients and methods. This prospective observational study was conducted at Z.A.Bashlyaeva Children's City Clinical Hospital, Moscow Healthcare Department and included 107 children with IM. Laboratory testing was performed at the Department of Virological Diagnostics, National Medical Research Center for Hematology, Ministry of Health of the Russian Federation. Results. IM is a polyetiologic disease. So far, researchers have failed to find a significant correlation between clinical manifestations of IM and its etiology and phase of infection. Patients with IM caused by primary monoinfection with Epstein–Barr virus (EBV) are at high risk of developing chronic EBV infection. Neutrophilia is a typical laboratory sign of IM during the acute phase of it. Conclusion. The improvement of IM diagnosis with a detailed evaluation of clinical and laboratory criteria, as well as risk assessment of unfavorable outcome are currently impossible without the identification of both disease etiology and phase of infection. Key words: human herpes virus VI, Epstein–Barr virus, children, infectious mononucleosis, cytomegalovirus

Plasmocytoid dendritic cells (pDCs) play a key role in immunity against most viruses, given their unparalleled ability to produce large amounts of IFN I type. Studies aimed at studying pDCs in Epstein-Barr virus infection (EBV) are still few. The outcome of EBV largely depends on the ability of the patient’s immune system to form an adequate immune defense, that provides not only a rapid recovery, but also prevents the prolonged course of the disease, leading to the development of immune deficiency and other complications. The development of effective immunorehabilitation of EBV, able to prevent the chronization of this disease, remains one of the most important areas of scientific and practical activities.