This retrospective-prospective longitudinal observational study was designed to evaluate the role of bedside lung ultrasound per se and in association with hemogasanalysis parameters in predicting the severity of COVID-19 patients in the Emergency Departement (ED).

Retrospective data regarding patients who presented at the ED of IRCCS San Raffaele Hospital from 10/11/2020, together with those acquired by the observation of patients who will access to the ED until 10/05/2021 will be collected, configuring a total enrollment period of 6 months.

Clinical informations about patients' medical history will be recorded, with particular focus on the type and date of onset of the symptoms. The diagnostic and therapeutic strategy will be chosen according to the current standard of care. Results of bedside lung ultrasound, together with vital parameters, blood gas analysis, laboratory and other findings will be recorded.

The primary outcome will be defined as patients' outcome at time of discharge from the ED, in terms of intensity of required care (home discharge, low or high-intensity care hospitalization, death). Secondary outcomes will be patients' prognosis 30 days after access to ED and the required intensity of care (eg need for non-invasive ventilation, oro-tracheal intubation).The follow-up 30 days after access to the ED will be evaluated by telephone survey or by consulting medical records.

Inclusion Criteria:

• SARS - CoV 2 infection confirmed by positive RT-PCR on nasopharyngeal swab

Exclusion Criteria:

• impossibility to perform lung ultrasound due to technical limitations.

Adult patients admitted to IRCCS San Raffaele Hospital Emergency Departement with SARS CoV-2 documented infection from 10/11/2020 to 10/05/2021.