Table 1. Parameter Values that vary among the five COVID-19 Pandemic Planning Scenarios. The scenarios are intended to advance public health preparedness and planning. They are not predictions or estimates of the expected impact of COVID-19. The parameter values in each scenario will be updated and augmented over time, as we learn more about the epidemiology of COVID-19. Additional parameter values might be added in the future (e.g., population density, household transmission, and/or race and ethnicity).
Parameter values are based on data received by CDC prior to 4/29/2020
| Parameter | Scenario 1 | Scenario 2 | Scenario 3 | Scenario 4 | Scenario 5:
Current Best Estimate |
|---|---|---|---|---|---|
| R0
Source: Preliminary COVID-19 estimates, ASPR and CDC |
2 | 2 | 3 | 3 | 2.5 |
| Symptomatic Case Fatality Ratio, stratified by age in years
Source: Preliminary COVID-19 estimates, CDC |
0-49: 0.0002 |
0-49: 0.0002 |
0-49: 0.001 |
0-49: 0.001 |
0-49: 0.0005 |
|
50-64: 0.001 |
50-64: 0.001 |
50-64: 0.006 |
50-64: 0.006 |
50-64: 0.002 |
|
|
65+: 0.006 |
65+: 0.006 |
65+: 0.032 |
65+: 0.032 |
65+: 0.013 |
|
|
Overall: 0.002 |
Overall: 0.002 |
Overall: 0.010 |
Overall: 0.010 |
Overall: 0.004 |
|
| Symptomatic Case Hospitalization Ratio, stratified by age in years
Source: Preliminary COVID-19 estimates, CDC |
0–49: 0.013 |
0–49: 0.013 |
0–49: 0.026 |
0–49: 0.026 |
0–49: 0.017 |
|
50–64: 0.036 |
50–64: 0.036 |
50–64: 0.057 |
50–64: 0.057 |
50–64: 0.045 |
|
|
65+: 0.052 |
65+: 0.052 |
65+: 0.10 |
65+: 0.10 |
65+: 0.074 |
|
|
Overall: 0.028 |
Overall: 0.028 |
Overall: 0.041 |
Overall: 0.041 |
Overall: 0.034 |
|
| Percent of infections that are asymptomatic
Source: Preliminary COVID-19 estimates, ASPR and CDC |
20% | 50% | 20% | 50% | 35% |
| Infectiousness of asymptomatic individuals relative to symptomatic individuals
Source: Assumption, ASPR and CDC |
50% | 100% | 50% | 100% | 100% |
Table 2. Parameter Values Common to the Five COVID-19 Pandemic Planning Scenarios. The parameter values are likely to change as we obtain additional data about disease severity and viral transmissibility of COVID-19.
Parameter values are based on data received by CDC prior to 4/29/2020
| Pre-existing immunity
Source: Assumption, ASPR and CDC |
No pre-existing immunity before the pandemic began in 2019. It is assumed that all members of the U.S. population were susceptible to infection prior to the pandemic. |
|---|---|
| Percentage of transmission occurring prior to symptom onset:
Source: Preliminary COVID-19 estimates, ASPR and CDC |
40% |
| Time from exposure to symptom onset
Source: Pre-publication COVID-19 estimates* |
~6 days (mean) |
| Time between symptom onset in an individual and symptom onset of a second person infected by that individual
Source: Pre-publication COVID-19 estimates |
~6 days (mean) |
| Parameter Values Related to Healthcare Usage | |
| Time to seek care (outpatient)
Source: Survey of persons with Influenza like illness (ILI), CDC† |
≤2 days: 35% 3–7 days: 50% ≥8 days: 25% |
| Mean number of days from symptom onset to hospitalization (standard deviation)
Source: Preliminary COVID-19 estimates, CDC§ |
0-49 years: 6.9 (5.0) days 50-64 years: 7.2 (5.3) days ≥65 years: 6.2 (5.7) days |
| Mean number of days of hospitalization among those not admitted to ICU (standard deviation) ¶
Source: Preliminary COVID-19 estimates, CDC |
0-49 years: 3.9 (3.7) days 50-64 years: 4.9 (4.3) days ≥65 years: 6.3 (5.1) days |
| Mean number of days of hospitalization among those admitted to ICU (standard deviation) ¶
Source: Preliminary COVID-19 estimates, CDC |
0-49 years: 9.5 (7.2) days 50-64 years: 10.5 (7.0) days ≥65 years: 10.0 (6.8) days |
| Percent admitted to ICU among those hospitalized
Source: Preliminary COVID-19 estimates, CDC |
0-49 years: 21.9% 50-64 years: 29.2% ≥65 years: 26.8% |
| Percent on mechanical ventilation among those in ICU
Source: Preliminary COVID-19 estimates, CDC |
0-49 years: 72.1% 50-64 years: 77.6% ≥65 years: 75.5% |
| Mean number of days of mechanical ventilation (standard deviation)
Source: Preliminary COVID-19 estimates, CDC |
Overall: 5.5 (5.3) days |
| Mean number of days from symptom onset to death (standard deviation)
Source: Preliminary COVID-19 estimates, CDC§ |
0-49 years: 14.9 (7.7) days 50-64 years: 15.3 (8.1) days ≥65 years: 12.9 (7.6) days |
| Mean number of days from death to reporting (standard deviation)
Source: Preliminary COVID-19 estimates, CDC** |
0-49 years: 7.1 (7.7) days 50-64 years: 7.2 (7.7) days ≥65 years: 6.6 (7.3) days |
*Khalili, M., Karamouzian, M., Nasiri, N., Javadi, S., Mirzazadeh, A., & Sharifi, H. (2020). Epidemiological Characteristics of COVID-19: A Systemic Review and Meta-Analysis. medRxiv.
† Biggerstaff, M., Jhung, M. A., Reed, C., Fry, A. M., Balluz, L., & Finelli, L. (2014). Influenza-like illness, the time to seek healthcare, and influenza antiviral receipt during the 2010–2011 influenza season—United States. The Journal of infectious diseases, 210(4), 535-544.
§ Estimates only include onset dates between March 1, 2020 – March 31, 2020 to ensure cases have had sufficient time to observe the outcome (hospital admission or death).
¶ Estimates only include hospital admission dates between March 1, 2020 – March 31, 2020 to ensure cases have had sufficient time to observe the outcome (hospital discharge or death).
** Estimates only include death dates between March 1, 2020 – March 31, 2020 to ensure sufficient time for reporting.