05-19-2020, 12:19 PM
Funny enough, I just found an old hard drive with a presentation I gave to the pulmonary fellows at UCSF back in 2007 about the SARS epidemic. From my basic epidemiology class:
θ is proportion of transmissions that occur prior to the onset of symptoms
Isolation of symptomatic patients is successful if proportion of patients isolated (ε):ε > (1–1 /R[0])/(1–θ)
Can never be reached if R[0]θ > 1
I think there is evidence that θ is on the order of 50% for COVID-19 (might be as low as 25%, or as high and possibly even higher than 75%). R[0] is estimated at 2-3, so plugging in 2.5, you get 1.2. Thus, isolation only of symptomatic patients wouldn't be expected to work, and you are going to have to find and isolate some asymptomatic patients. Fortunately, you don't have to isolate all asymptomatic patients, just enough to break enough transmission chains to bring R below 1.
BC
θ is proportion of transmissions that occur prior to the onset of symptoms
Isolation of symptomatic patients is successful if proportion of patients isolated (ε):ε > (1–1 /R[0])/(1–θ)
Can never be reached if R[0]θ > 1
I think there is evidence that θ is on the order of 50% for COVID-19 (might be as low as 25%, or as high and possibly even higher than 75%). R[0] is estimated at 2-3, so plugging in 2.5, you get 1.2. Thus, isolation only of symptomatic patients wouldn't be expected to work, and you are going to have to find and isolate some asymptomatic patients. Fortunately, you don't have to isolate all asymptomatic patients, just enough to break enough transmission chains to bring R below 1.
BC