Clinical Presentation
Similar to SARS‐CoV, SARS‐CoV‐2 binds to angiotensin‐converting enzyme 2 (ACE2) receptors for entry via endocytosis into alveolar epithelial cells, as well as other cells with ACE2 receptors in the heart, gastrointestinal tract, and kidneys. 2 ,  4  COVID‐19 results from SARS‐CoV‐2 replication, causing early cell death (i.e., apoptosis) and provoking a storm of proinflammatory cytokines (e.g., interleukin‐6 [IL‐6]) disrupting alveolar walls with resulting fluid accumulation in alveoli. 4
The incubation period from infection to onset of COVID‐19 disease is typically 5 to 7 days (range 1‐14 days). 1 ,  2 ,  7  The most common symptoms of COVID‐19 are fever and nonproductive cough (Table 1). 1 ,  4 ,  7 ,  9  The Centers for Disease Control and Prevention (CDC) recently added anosmia and ageusia, the loss of smell and taste, as COVID‐19 symptoms. 7  Laboratory findings are remarkable for a normal leukocyte count, lymphopenia, and elevated C‐reactive protein. 1 ,  6 ,  8  Most hospitalized patients with COVID‐19 have a bilateral ground‐glass appearance on chest computed tomography (CT) scan consistent with viral pneumonia.
Table 1  Clinical Features of COVID‐19 in Wuhan and Multiple Other Locations in China
Clinical Features  Wuhan, China  Multiple Locations, China
Number of patients  10,999  3,062
Symptoms
Fever  89%  80%
Cough  68%  63%
Expectoration  34%  42%
Dyspnea  19%  34%
Fatigue/Myalgia  38%  46%
Headache  14%  15%
Nausea/Vomiting  5%  10%
Diarrhea  4%  13%
Laboratory results
Leukocytes in normal range  94%  70%
Lymphopenia  83%  57%
Increased C‐reactive protein  61%  74%
Alanine aminotransferase above upper limit of normal  21%  29%
Imaging
Abnormal chest CT  86%  89%
Bilateral infiltrates (ground glass)  56%  76%
Acute respiratory distress syndrome  6%  20%
Mortality  1.4%  6%
Data are from Guna et al. 1  and Centers for Disease Control and Prevention. 7
John Wiley & Sons, Ltd This article is being made freely available through PubMed Central as part of the COVID-19 public health emergency response. It can be used for unrestricted research re-use and analysis in any form or by any means with acknowledgement of the original source, for the duration of the public health emergency. Today, reverse transcription polymerase chain reaction (RT‐PCR) is the COVID‐19 diagnostic test. 2 ,  7  RT‐PCR sensitivity is highest for testing bronchial alveolar lavage fluid (93%) and declines for sputum (72%) and nasal swab (63%) specimens. 10  COVID‐19 diagnosis might require repeat testing. 2 ,  7  Serological tests to detect SARS‐CoV‐2 IgM and IgG antibodies are available. However, because of test sensitivity and other quality concerns, the US Food and Drug Administration (FDA; https://www.fda.gov) advises current serological tests are best used for surveillance and research, and not as the sole basis for COVID‐19 diagnosis.
COVID‐19 is commonly a mild disease. Of the first 72,314 COVID‐19 disease reported in China, 81% had no or mild pneumonia, 21% had severe dyspnea and radiological evidence of pulmonary disease, and 5% progressed to SARS. 1  Individuals can be ill for a week or longer before experiencing severe symptoms.
The risk for severe COVID‐19 disease is highest for men, older adults, and patients with certain comorbidities. In the United States, 80% of reported COVID‐19–related deaths are among people aged ≥65 years. 7 ,  9 ,  11  Deaths are rare among persons <24 years of age. 1 ,  7 ,  11  In the United States, most hospitalized patients with COVID‐19 have comorbid conditions, including obesity, hypertension, diabetes, and cardiovascular disease 7 ,  11  (Table 2). Although listed by the CDC as a comorbid condition associated with severe COVID‐19, chronic liver disease, including cirrhosis, has not been a common comorbidity associated with hospitalization in the United States (Table 2). The high prevalence of comorbid conditions can explain, in part, African Americans’ increased risk for hospitalization with COVID‐19 disease. 5  Variable comorbidity prevalence contributes to differences in national COVID mortality. Globally, crude fatality rates for COVID‐19 range from 0.2% in Singapore, to 2.0% to 3.0% in South Korea and Germany, to 4.3% for the United States, and to 10% to 13% in Spain, Italy, and the United Kingdom. 2 ,  5
Table 2  Comorbidities Among Persons With COVID‐19 Disease, United States
Condition  United States*  New York City
Not Hospitalized  Hospitalized  Intensive Care  Hospitalized
Patients  5143  1037  457  5700
One or more condition  27%  71%  78%  88%
Obesity     42%
Hypertension     57%
Diabetes mellitus  6%  24%  32%  34%
Cardiovascular disease  5%  23%  29%  18%
Chronic renal disease  1%  9%  12%  0.6%
Chronic liver disease  1%  1%  2%  9%
Immunocompromised  3%  6%  9%  2%
Mortality     21%
Total     21%
1 Comorbidity     88%
*  Based on data from the CDC for all 50 states and territories. Otherwise, data are Richardson et al. 11
John Wiley & Sons, Ltd This article is being made freely available through PubMed Central as part of the COVID-19 public health emergency response. It can be used for unrestricted research re-use and analysis in any form or by any means with acknowledgement of the original source, for the duration of the public health emergency. The search for effective therapies and a vaccine is occurring at a remarkable pace, with at least 29 studies of therapeutic agents and 5 studies of candidate vaccines registered on ClinicalTrials.org (https://www.clinicaltrials.gov). On May 1, 2020, the FDA granted Emergency Use Authorization of remdesivir, a broad‐spectrum antiviral nucleotide prodrug for treatment of severe COVID‐19. Studies of monoclonal antibodies against IL‐6 and hyperimmune immunoglobulin are in progress. Following reports of serious cardiac arrythmias, the FDA cautioned clinicians of prescribing hydroxychloroquine or chloroquine for treatment of COVID‐19. A safe and effective vaccine, if successfully developed, probably will not be available for 12 to 18 months.