Clinical Course

Illness Severity

The largest cohort of >44,000 persons with COVID-19 from China showed that illness severity can range from mild to critical:³⁸

• Mild to moderate (mild symptoms up to mild pneumonia): 81%
• Severe (dyspnea, hypoxia, or >50% lung involvement on imaging): 14%
• Critical (respiratory failure, shock, or multiorgan system dysfunction): 5%

In this study, all deaths occurred among patients with critical illness and the overall case fatality rate was 2.3%.³⁸ The case fatality rate among patients with critical disease was 49%.³⁸ Among children in China, illness severity was lower with 94% having asymptomatic, mild or moderate disease, 5% having severe disease, and <1% having critical disease.¹⁴ Among U.S. COVID-19 cases with known disposition, the proportion of persons who were hospitalized was 19%.³⁹ The proportion of persons with COVID-19 admitted to the intensive care unit (ICU) was 6%.³⁹

Clinical Progression

Among patients who developed severe disease, the medium time to dyspnea ranged from 5 to 8 days, the median time to acute respiratory distress syndrome (ARDS) ranged from 8 to 12 days, and the median time to ICU admission ranged from 10 to 12 days.^5,6,10,11 Clinicians should be aware of the potential for some patients to rapidly deteriorate one week after illness onset. Among all hospitalized patients, a range of 26% to 32% of patients were admitted to the ICU.^6,8,11 Among all patients, a range of 3% to 17% developed ARDS compared to a range of 20% to 42% for hospitalized patients and 67% to 85% for patients admitted to the ICU.^1,4-6,8,11 Mortality among patients admitted to the ICU ranges from 39% to 72% depending on the study.^5,8,10,11 The median length of hospitalization among survivors was 10 to 13 days.^1,6,8

Risk Factors for Severe Illness

Age is a strong risk factor for severe illness, complications, and death.^{1,6,8,10,11,38-41} Among more than 44,000 confirmed cases of COVID-19 in China, the case fatality rate was highest among older persons: ≥80 years: 14.8%, 70–79 years: 8.0%, 60–69 years: 3.6%, 50–59 years: 1.3%, 40–49 years: 0.4%, <40 years: 0.2%.^38,42 Early U.S. epidemiologic data suggests that the case fatality was highest in persons aged ≥85 years (range 10%–27%), followed by 3%–11% for ages 65–84 years, 1%–3% for ages 55–64 years, and <1% for ages 0–54 years.³⁹

Patients in China with no reported underlying medical conditions had an overall case fatality of 0.9%, but case fatality was higher for patients with comorbidities: 10.5% for those with cardiovascular disease, 7.3% for diabetes, and approximately 6% each for chronic respiratory disease, hypertension, and cancer.⁴² Heart disease, hypertension, prior stroke, diabetes, chronic lung disease, and chronic kidney disease have all been associated with increased illness severity and adverse outcomes.^{1,6,10,11,38,42,43} Accounting for differences in age and prevalence of underlying condition, mortality associated with COVID-19 in the United States was similar to China.^24,39,40

Reinfection

There are no data concerning the possibility of re-infection with SARS-CoV-2 after recovery from COVID-19. Viral RNA shedding declines with resolution of symptoms, and may continue for days to weeks.^10,33,34 However, the detection of RNA during convalescence does not necessarily indicate the presence of viable infectious virus. Clinical recovery has been correlated with the detection of IgM and IgG antibodies which signal the development of immunity.^36,44-46

Source: https://tools.cdc.gov/api/embed/downloader/download.asp?m=404952&c=407492