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  • Asymptomatic in approximately 20–35% of adults and most children.

  • When symptomatic, adults often have upper respiratory tract illness with fever and cough.

  • Advanced pulmonary complications (pneumonia, acute respiratory distress syndrome [ARDS]) occur with fulminant disease.

  • Mortality of 1–21% (varied by geographic area and strain).

  • High predilection for the elderly, the immunocompromised, those with chronic diseases, those living in crowded conditions.

General Considerations

In late 2019, a novel coronavirus emerged, spreading quickly from China across the globe. The virus was initially named “novel coronavirus 2019” (2019-nCoV), accounting for the year of discovery, its status as a “novel” virus, and its family name (coronavirus, CoV). The CDC-recommended terminology for the virus is SARS-CoV-2, and the illness caused by this virus is called “Coronavirus Disease 2019” or COVID-19.

Coronaviruses are a large family of viruses commonly found in humans as well as many other species of animals, including bats, camels, cattle, and cats. There are four genera of coronaviruses, of which only the alphacoronaviruses (coronavirus NL63 and 229E) and the betacoronaviruses affect humans. Like SARS-CoV-1, MERS-CoV, and the human common cold coronaviruses HC43 and HKU1, the SARS-CoV-2 virus is a betacoronavirus. SARS-CoV-1 and MERS-CoV were identified 7 and 17 years, respectively, before SARS-CoV-2 was identified. All coronaviruses likely originated in bats. The spread of SARS-CoV-2 from bats was perhaps amplified by pangolins, an Asian anteater whose scales are traded on black markets for circulatory problems, although this theory remains under investigation. Antibodies to SARS-CoV-2 have been identified in bats over a 4800 km range in Asia as well as in pangolins at a wildlife checkpoint station in southern Thailand. A WHO investigative team was unable to implicate a specific area of Wuhan as the origin of the outbreak and further geo-epidemiologic studies are needed.

A potential role of mink is under study, with mink farms being a secondary and transmitting source of SARS-CoV-2 infections in the Netherlands; mink farms are recognized as potential sources of human infection in seven other European countries and the United States. Transmission to humans does not appear to regularly occur with cats and dogs, who are also secondarily infected by humans although a new coronavirus canine-feline recombinant is reported from a Malaysian patient with pneumonia.

A. Epidemiology

Early in the outbreak, most fatalities were from Wuhan and other parts of the Hubei province. As cases were reported from other countries, COVID-19 was declared a pandemic by the WHO on March 11, 2020. By early March 2020, case numbers outside of China were growing faster than inside China (see the Johns Hopkins Coronavirus Resource Center website for specifics at a given time,

While SARS-CoV-2 antibodies have been identified in retrospective ...

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