INTRODUCTION

• Coronaviruses are important human and animal pathogens. At the end of 2019, a novel coronavirus was identified as the cause of a cluster of pneumonia cases in Wuhan, a city in the Hubei Province of China. It rapidly spread, resulting in an epidemic throughout China, followed by an increasing number of cases in other countries throughout the world.

•  In February 2020, the World Health Organization designated the disease COVID-19, which stands for coronavirus disease 2019. The virus that causes COVID-19 is designated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); previously, it was referred to as 2019-nCoV.

• VIROLOGY: Full-genome sequencing and phylogenic analysis indicated that the coronavirus that causes COVID-19 is a betacoronavirus in the same subgenus as the severe acute respiratory syndrome (SARS) virus (as well as several bat coronaviruses), but in a different clade.

•  The structure of the receptor-binding gene region is very similar to that of the SARS coronavirus, and the virus has been shown to use the same receptor, the angiotensin-converting enzyme 2 (ACE2), for cell entry. The Coronavirus Study Group of the International Committee on Taxonomy of Viruses has proposed that this virus be designated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

EPIDEMIOLOGY

• Geographic distribution — Globally, more than five million confirmed cases of COVID-19 have been reported.

• Since the first reports of cases from Wuhan, a city in the Hubei Province of China, at the end of 2019, cases have been reported in all continents, except for Antarctica.

• In the United States, COVID-19 has been reported in all 50 states, Washington DC, and at least four territories. The cumulative incidence varies by state and likely depends on a number of factors, including population density and demographics, extent of testing and reporting, and timing of mitigation strategies. In the United States, outbreaks in long-term care facilities and homeless shelters have emphasized the risk of exposure and infection in congregate settings.

PATHOPHYSIOLOGY

•  Incubation period — The incubation period for COVID-19 is thought to be within 14 days following exposure, with most cases occurring approximately four to five days after exposure.

• The median incubation period in this study was 5.1 days.

• Spectrum of illness severity and case fatality rates — The spectrum of symptomatic infection ranges from mild to critical; most infections are not severe. Specifically, in a report from the Chinese Center for Disease Control and Prevention that included approximately 44,500 confirmed infections with an estimation of disease severity.

• Mild (no or mild pneumonia) was reported in 81 percent.

• Severe disease (eg, with dyspnea, hypoxia, or >50 percent lung involvement on imaging within 24 to 48 hours) was reported in 14 percent.

• Critical disease (eg, with respiratory failure, shock, or multiorgan dysfunction) was reported in 5 percent.

• The overall case fatality rate was 2.3 percent; no deaths were reported among noncritical cases.

In late 2019, a novel coronavirus, now designated SARS-CoV-2, was identified as the cause of an outbreak of acute respiratory illness in Wuhan, a city in China. In February 2020, the World Health Organization (WHO) designated the disease COVID-19, which stands for coronavirus disease 2019.

DISCUSSION

●Since the first reports of COVID-19, infection has spread to include more than five million confirmed cases worldwide, prompting the WHO to declare a public health emergency in late January 2020 and characterize it as a pandemic in March.

●The possibility of COVID-19 should be considered primarily in patients with fever and/or respiratory tract symptoms who reside in or have traveled to areas with community transmission or who have had recent close contact with a confirmed or suspected case of COVID-19

●The microbiologic diagnosis is made by a positive nucleic acid amplification test (eg, reverse transcription polymerase chain reaction [RT-PCR]) for SARS-CoV-2. An upper respiratory tract specimen is the preferred initial test specimen. If possible, all symptomatic patients with suspected infection should undergo testing. However, because of limited testing capacity and concern for false-negative testing, the diagnosis is often presumptively made based on consistent clinical and epidemiologic features. Serologic tests can help identify individuals with prior infection but have less utility in the first weeks of infection.

●Upon suspicion of COVID-19, infection control measures should be implemented. Infection control in the home and in health care settings is discussed in detail elsewhere.

CONCLUSION

●Home management is appropriate for patients with mild illness who can adequately self-isolate in the outpatient setting. A minority of patients need critical care. Home, hospital, and intensive care unit management of patients with COVID-19 is discussed in detail elsewhere.

●To reduce the risk of transmission in the community, individuals should be advised to wash hands diligently, practice respiratory hygiene (eg, cover their cough), and avoid crowds and close contact with ill individuals, if possible. Social distancing is recommended in locations that have community transmission. In some locations, face coverings are advised in public settings.

Limitations in testing capacity may preclude testing all patients with suspected infection; suggested priorities include hospitalized patients and symptomatic individuals who are health care workers or first responders, work or reside in congregate living settings, or have risk factors for severe disease.