COVID-19 - multisystem disease.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for coronavirus disease 2019 (COVID-19), caused a global public health crisis, with a significant impact on multiple body systems. This virus, a member of the Coronaviridae family, shows ~80% genomic similarity to SARS-CoV and ~50% genomic similarity to Middle East respiratory syndrome coronavirus (MERS-CoV). The spike (S) protein plays an essential role in the pathogenesis of the virus, as it facilitates its entry into host cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor. In addition to the respiratory system damage, SARS-CoV-2 infection causes a variety of gastrointestinal (GI), neurological, cardiovascular (CV), ocular, renal, etc. clinical manifestations. Neurological complications, such as anosmia, ague, headache, encephalitis and cerebrovascular events, were frequently observed, being attributed to both direct viral invasion and a very strong systemic inflammatory response. GI symptoms such as diarrhea, nausea and vomiting are common and may occur independently of respiratory symptoms, and the presence of viral ribonucleic acid (RNA) detected in fecal samples suggests possible fecal-oral transmission. The CV system is affected by myocardial damage, inflammation and coagulation disorders, with an increased risk of thromboembolic events. At the ocular level, the virus was identified in ocular secretions, and conjunctivitis, uveitis and episcleritis were observed in about 11% of patients. Renal involvement, manifested by acute kidney injury, was detected in 0.5-7% of cases. In conclusion, SARS-CoV-2 infection is not limited to respiratory tract involvement but also has significant systemic implications.