COVID-19: laboratory diagnosis for clinicians. An updating article.

COVID-19 (coronavirus disease 2019) is an infectious disease caused by the new coronavirus associated with severe acute respiratory syndrome 2 (SARS-CoV-2). Coronaviridae comprises a large family, of which at least seven members are known to cause respiratory diseases in humans. Coronaviruses have the ability to infect virtually all major groups of animals and, eventually, can infect humans. SARS-CoV-2 is the third coronavirus to cross the species barrier and infect humans. This virus was identified in an outbreak of pneumonia cases in Wuhan city, Hubei province, China, in December 2019. Its entire genome is inscribed on a single strand of ribonucleic acid. Some proteins present on the surface of the virus act as facilitators for its entry into host cells, while others, apparently, are related to its pathogenesis. Coronaviruses are responsible for respiratory infections in humans and some animals. The infection is often mild to moderate in intensity, but some coronaviruses may cause serious illnesses, such as severe acute respiratory syndrome (SARS), which occurred in 2002, and the Middle East respiratory syndrome (MERS). Coronaviruses can activate an excessive and unregulated immune response, which may promote SARS development. Although the lungs are one of the target organs, the hypoxia mechanism is systemic and other organs begin to suffer both through lack of oxygen and through deregulation of inflammation control mechanisms.