Infectious mononucleosis (LM) is an acute proliferative infectious disease of the monocyte-macrophage system that is common in the pediatric period. It is mainly caused by EBV. It is characterized by irregular fever, pharyngitis, enlarged lymph nodes and liver and spleen, large numbers of abnormal lymphocytes in the blood, and the presence of heterophilic agglutinins and EBV-specific antibodies in the serum.
The cause of this disease is EBV, which was first identified in 1964 by E and B from cell cultures of African children with malignant lymphoma and was named EBV. EBV belongs to the herpesvirus group and is a virus that infects humans universally and has latent and transforming properties. The virus was first identified as the cause of LM in 1968. The basis for EBV being the cause of the disease is that ① the virus can only grow and proliferate in the cells of the lymphocyte system, ② the virus can stimulate the proliferation of lymphocytes during culture, ③ EBV can be cultured in the peripheral blood lymphocytes of children in the acute phase, ④ the patient has high titers of EBV-specific antibodies in the serum, and the well can exist for a long time, ⑤ those without such specific antibodies are susceptible to the disease, and those with positive antibodies are not. (5) those without such specific antibodies are susceptible to the disease, while those with positive antibodies do not develop it.
More than 90% of LM cases with similar clinical symptoms are caused by EBV, while the other 5-10% of cases called infectious mononucleosis are caused by cytomegalovirus (CMV), Toxoplasma gondii, adenovirus, hepatitis virus, HIV, and herpesvirus type 6 (HHV-6).
Epidemiology The disease is widespread, mostly disseminated, and can also be small epidemic, transmitted by close contact with oral saliva of patients. Droplet transmission is not important, and blood and stool transfusions are also a source of infection. The disease is usually seen in older children and adolescents, but it can be non-disclosed in children under 6 years of age. Infection in early childhood is more common in areas with poor sanitation; conversely, it is more common in adolescence in areas with better conditions. In adulthood, serum antibodies are mostly positive, and EBV can be found not only in the saliva of children, but also in the saliva of 20% of children recovering from the disease and 50% of those receiving immunotherapy because of positive antibodies, so it is thought that the virus can multiply in the oral cavity. The pathogen can be transmitted from the incubation period to 6 months or more after the disease; even 15% of recovered patients with only serologically confirmed disease can still intermittently excrete the virus.
Another possible route of transmission has been suggested as vertical transmission, as EBV was found in the lymph nodes of a two-week-old neonate who died from the disease.
Since most transmission is by direct contact, there is no need to be overly concerned about droplet transmission in schools, but transmission in the home is more likely. There is no practical way to prevent this disease.
Pathological changes After entering the oral cavity, the virus multiplies and replicates in the lymphoid tissues of the pharynx and then enters the bloodstream to produce viremia, which mainly affects the lymphoid tissues and tissues with lymphocytes and internal organs. (Pharyngeal epithelial cells, B cells, T cells and NK cells all have receptors for EBV). However, IM primarily infects B cells (T cells are difficult sites for long-term latent EBV presence) and subsequently causes a strong T cell response, resulting in the formation of abnormal lymphocytes, or activated suppressor T cells, that can be seen in the peripheral blood. The main pathological histological change in this disease is benign proliferation of lymphoid tissue, which does not septicize. The liver, spleen, myocardium, kidneys, adrenal glands, lungs, and central nervous system can be involved, manifesting as abnormal lymphocyte infiltration.