COVID-19 in children: current data and future perspectives

Coronaviruses (CoVs) are a large family of enveloped, single-stranded, zoonotic RNA viruses that represent one of the major pathogens that primarily targets the respiratory system. CoVs are divided into 4 genera: alpha, beta, delta, and gamma; alpha and beta CoVs are known to infect humans (human coronaviruses HCoVs). They resulted previously in the severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERSCoV). Since December 2019, a novel CoV (SARSCoV-2) started to cause infections in humans, first reported in Wuhan, Hubei province, China, with a cluster of patients presenting with pneumonia. Afterwards, the novel CoV has quickly spread throughout the world. Genomic analyses suggest that the 2019-nCoV sequencing is closely related to the bat SARSrelated CoV, but the pathogen was probably transmitted to humans by other animals which may have served as intermediate hosts facilitating the virus recombination and mutation, further adding to its genetic diversity.Two different types of 2019nCoV were identified, designated type L (accounting for 70 % of the strains) and type S (accounting for 30 %) but the difference between the two strains and clinical implications remain to be determined. The L type predominated during the early days of the epidemic in China but accounted for a lower proportion of strains outside of Wuhan.