13.1% have severe disease [...] and 6.1% are critical. [...]
Severe cases are defined as tachypnoea (≧30 breaths/ min) or oxygen saturation ≤93% at rest, or PaO2/FIO2 <300 mmHg. Critical cases are defined as respiratory failure requiring mechanical ventilation, shock or other organ failure that requires intensive care. About a quarter of severe and critical cases [i.e. about the number of critical cases] require mechanical ventilation while the remaining 75% require only oxygen supplementation.
As far as we can tell, these proportions for severe and critical symptoms are at hospital admission. Mark I first made this estimate here; we have updated downwards since then on estimates of untreated mortality on weak evidence that the current international strain is less severe than Hubei’s, and slightly upwards as testing in China and other East Asian countries becomes more thorough with fewer additional mild cases than we thought.
Also note that the 70% mortality without a ventilator/o2 for critical cases was assuming the basic medical care of an overcrowded hospital, even if equipment is not available. Medical care for pneumonia is primarily supportive, but doctors I’ve talked to say there is significant risk of developing complications like sepsis that require admission. This introduces more uncertainty into our estimates due to the number of moving parts.
Here’s the quotes we used; from pages 12 and 32.
As far as we can tell, these proportions for severe and critical symptoms are at hospital admission. Mark I first made this estimate here; we have updated downwards since then on estimates of untreated mortality on weak evidence that the current international strain is less severe than Hubei’s, and slightly upwards as testing in China and other East Asian countries becomes more thorough with fewer additional mild cases than we thought.
Also note that the 70% mortality without a ventilator/o2 for critical cases was assuming the basic medical care of an overcrowded hospital, even if equipment is not available. Medical care for pneumonia is primarily supportive, but doctors I’ve talked to say there is significant risk of developing complications like sepsis that require admission. This introduces more uncertainty into our estimates due to the number of moving parts.