CDC's "best estimate" "based on data received by CDC prior to 4/29/2020"

https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scenarios.html
R0: 2.5

Percent of infections that are asymptomatic: 35%

Infectiousness of asymptomatic individuals relative to symptomatic individuals: Same

**Symptomatic** Case Fatality Ratio: 0.4%

**Symptomatic** Case Hospitalization Ratio: 3.4%

Percent admitted to ICU among those hospitalized: 0-49 years: 21.9%,

**50-64 years: 29.2%**, ≥65 years: 26.8%

Percent on mechanical ventilation among those in ICU: 0-49 years: 72.1%,

**50-64 years: 77.6%**, ≥65 years: 75.5%

Percentage of transmission occurring prior to symptom onset: 40%

Time from exposure to symptom onset: ~6 days (mean)

Time between symptom onset in an individual and symptom onset of a second person infected by that individual: ~6 days (mean)

Time to seek care (outpatient): 3–7 days: 50%

Mean number of days from symptom onset to hospitalization: 6-7 days

Mean number of days of hospitalization among those not admitted to ICU: 4-6 days

Mean number of days of hospitalization among those admitted to ICU: ~10 days

Mean number of days of mechanical ventilation: 5.5 days

Mean number of days from symptom onset to death: ~14 days

Mean number of days from death to reporting:

**~7 days**
I highlighted some interesting things, like the fact that hospitalized 50-64-year-olds are more likely to be admitted to ICU than those over 65, and deaths are reported after a delay of about a week.

The symptomatic Case Fatality Ratio of 0.4% appears to account for undiagnosed cases, so it's more like an Infection Fatality Rate. Otherwise, if you divide the ~2000 daily deaths by ~30,000 daily reported cases in April, you get a 6.7% CFR.

If the symptomatic IFR is 0.4%, and 35% of infections are asymptomatic and presumably not fatal, then the overall IFR is 0.26%, which would mean that 99K deaths resulted from 38 million infections, which would be 23 times greater than the 1.67 million reported cases. It would mean that 11.5% of the U.S. population has already been infected despite lockdowns, which is a higher percentage than the ~4% I've seen in various serology studies and

projections, except in hot spots like NYC, where

27% may have been infected.