Novel coronavirus (SARS-CoV-2) infections
In December 2019, a novel coronavirus (SARS-CoV-2) was first isolated from three patients with pneumonia, connected to the cluster of acute respiratory illness cases from Wuhan, China. Genetic analysis revealed that it is closely related to SARS-CoV and genetically clusters within the genus Betacoronavirus, forming a distinct clade in lineage B of the subgenus Sarbecovirus together with two bat-derived SARS-like strains. The origin of the virus is not clear yet. Similar to SARS-CoV, a recent study confirmed that Angiotensin Converting Enzyme 2 (ACE 2), a membrane exopeptidase, is the receptor used by SARS-CoV-2 for entry into the human cells.
The virus was initially isolated in bronchoalveolar lavage fluid samples . RNA of the virus has also been detected in blood samples. So far, it is still unknown whether the virus is excreted in faeces or urine. In a report of a family cluster including six cases, RT-PCR was negative in urine and stool samples.
Information on the epidemiological and clinical characteristics of the infection caused by SARS-CoV-2 is accumulating. The Chinese Center for Disease Control and Prevention estimates the incubation period to be between three and seven days, with a range of up to 14 days. Their current estimate is that R0 is between 2 and 3. However, these estimates are still uncertain and are expected to be updated as more information becomes available.
In a first study of the clinical features of the infection (published 24 January 2020), most of the 41 hospitalised patients presented with fever, cough, and myalgia or fatigue. Diarrhoea was uncommon. More than half of the patients developed dyspnoea after a median of eight days from the onset of symptoms and 13 (32%) were admitted to an intensive care unit (ICU). Invasive mechanical ventilation was required in four (10%) patients and extracorporeal membrane oxygenation (ECMO) in two (5%). Computed tomography imaging of the chest identified in almost all cases bilateral abnormalities, such as ground-glass opacities and sub segmental areas of consolidation in the milder cases, and lobular and sub segmental consolidation in cases admitted to ICU.
So far, according to the WHO situation report of 27 January 2020, among the laboratory-confirmed cases, 17% are classified as severe. In the same report China accounts for 80 fatalities.
Reported case fatality rates range from 4% in the Statement of the WHO Emergency Committee, to 14% when only recovered cases and deaths are included in the denominator, and 15% in the publication of a small case series of hospitalised patients. A more recent study of 99 cases hospitalised between 1 January and 20 January, reported that as of 25 January 31% had been discharged, 11% had died, and 58% were still admitted with final outcomes unknown at this time.