**7. Pathogenesis**

The WHO have reported that data on the incidence and ramp prevalence of adenoviral infections are not exact, since in many cases, adenoviruses cause mild forms and therefore remain unregistered, according to general practitioners [16]. However, in recent years, adenoviruses caused widespread outbreaks in Asia [17–19] in which adenoviral infection was accompanied by the development of acute respiratory distress syndrome (ARDS) in Malaysia [18], China

**Clinical manifestations Serotype Ref.** Acute respiratory diseases 1, 7, 14, 21 [10] Viral pneumonia 1, 3, 4, 7, 55 [10–12] Conjunctivitis 3, 7, 8, 10, 14, 19, 37 [13] Gastroenteritis 9, 11, 31, 40, 41 [9, 14] Meningoencephalitis 2, 6, 7, 12, 32 [15]

The source of infection is a sick person in the acute stage of the disease, convalescent, or a virus carrier. Pathogens are secreted with nasopharyngeal secretions, sputum, conjunctival discharge, feces, and urine (mainly in individuals with immunosuppression). The timing of isolation of pathogens from the upper respiratory tract reaches the 25th day of illness onset and more than 1.5 months with feces. Adenoviral infections are transmitted by airborne, introducing the virus to the conjunctiva and possibly by the fecal-oral route, thus affecting not only the respiratory tract but also other organs. The widespread disease is 5–10% of all viral diseases. Incidence is recorded throughout the year with a rise in the cold season. Both sporadic cases and epidemic outbreaks are observed. The most susceptible to infection are children from 6 months to 5 years, as well as military personnel. Particularly it has a high incidence in the newly formed groups of children and adults (in the first 2–3 months). In 95% of the adult population, antibodies to the most common serotypes of the virus can be detected

The deproteinization of viruses entered the cell starts in the cytoplasm and ends in the nucleus, where DNA is released with a terminal protein attached to it. Transcription of the genome and replication of viral DNA occur in the nucleus with the help of cellular enzymes [21]. First, mRNAs are synthesized, which code for the synthesis of virus-specific enzymes and then also RNAs that carry information on the synthesis of capsid proteins and strands. The assembly

[16, 19], and South Korea [19].

**Table 1.** Clinical forms of adenovirus infection.

**5. Transmission**

4 Adenoviruses

in the serum [20].

**6. Reproduction**

From the pathogenetic point of view, adenoviruses damage the respiratory tract and belong to the "respiratory" viruses. However, adenoviruses also can cause lesions of the intestine and conjunctiva, as well as the central nervous system, bladder, and genitals. Adenoviruses multiply in the mucous membrane with a gradual, consistent involvement in the pathological process of the descending parts of the respiratory tract. Reproduction of adenoviruses also can occur in the intestinal tissue or lymph nodes which is accompanied by a multiple increase in lymph nodes. In addition to local changes, adenoviruses have a general toxic effect which appears as a fever and symptoms of general intoxication (weakness, lethargy, loss of appetite, headache, and nausea). The ability of adenoviruses to reproduce in the epithelial cells of the respiratory tract, conjunctiva, and intestine with the occurrence in some cases of hematogenous dissemination creates a wide range of clinical manifestations of this infection, including the appearance of generalized lymphadenopathy and widespread exanthema. In addition to adenoviruses in the genesis of acute pneumonia, the attachment of a secondary bacterial flora is important, which is facilitated by the suppression of the immune system [23–24].
