It’s based on a few facts and swirling them around in my intuition to choose a single simple number.
Long invisible contagious incubation period (seems somewhat indicated but maybe is wrong) and high degree of contagiousness (the Ro factor) implies it is hard to contain and should spread in the network (and look something like probability spreading in a Markov chain with transition probabilities roughly following transportation probabilities).
The exponential growth implies that we are only a few doublings away from world scale pandemic (also note we’re probably better at stopping things when their at small scale). In the exponential sense, 4,000 is half way between 1 and 8 million and about a third of the way to world population.
The exponential growth curve and incubation period also have implications about “bugging out” strategies where you get food and water, isolate, and wait for it to be over. Let’s estimate again:
Assuming as in the above comment we are 1⁄3 of the exponential climb (in reported numbers) towards the total world population and it took a month, in two more months (the end of March) we would expect it to reach saturation. If the infectious incubation period is 2 weeks (and people are essentially uniformly infectious during that time) then you’d move the two month date forward by two weeks (the middle of March). Assuming you don’t want to take many risks here you might have a week buffer in front (the end of the first week of March). Finally, after symptoms arise people may be infectious for a couple weeks (I believe this is correct, anyone have better data?). So the sum total amount of time for the isolation strategy is about 5 weeks (and may start as early as the end of the first week of March or earlier depending on transportation and supply disruptions).
Governments by detecting cases early or restricting travel, and citizens by isolating and using better hygiene, could change these numbers and dates.
(note: for future biorisks that may be more severe this reasoning is also useful)
It’s based on a few facts and swirling them around in my intuition to choose a single simple number.
Long invisible contagious incubation period (seems somewhat indicated but maybe is wrong) and high degree of contagiousness (the Ro factor) implies it is hard to contain and should spread in the network (and look something like probability spreading in a Markov chain with transition probabilities roughly following transportation probabilities).
The exponential growth implies that we are only a few doublings away from world scale pandemic (also note we’re probably better at stopping things when their at small scale). In the exponential sense, 4,000 is half way between 1 and 8 million and about a third of the way to world population.
The exponential growth curve and incubation period also have implications about “bugging out” strategies where you get food and water, isolate, and wait for it to be over. Let’s estimate again:
Assuming as in the above comment we are 1⁄3 of the exponential climb (in reported numbers) towards the total world population and it took a month, in two more months (the end of March) we would expect it to reach saturation. If the infectious incubation period is 2 weeks (and people are essentially uniformly infectious during that time) then you’d move the two month date forward by two weeks (the middle of March). Assuming you don’t want to take many risks here you might have a week buffer in front (the end of the first week of March). Finally, after symptoms arise people may be infectious for a couple weeks (I believe this is correct, anyone have better data?). So the sum total amount of time for the isolation strategy is about 5 weeks (and may start as early as the end of the first week of March or earlier depending on transportation and supply disruptions).
Governments by detecting cases early or restricting travel, and citizens by isolating and using better hygiene, could change these numbers and dates.
(note: for future biorisks that may be more severe this reasoning is also useful)
Have you looked at how long pandemics have lasted in the past? I think it’s a lot longer than five weeks.
It could have longer tail, but given high R0 large part of human population could be simultaneously ill (or self isolated) in March-April 2020.
What is you opinion, Dave, could this could put food production at risk?
Thanks. I’ve updated towards your estimate but 1⁄3 still seems high by my (all too human) intuitions.