The 90% might be conservative. If the rate of spread can be reduced by 50%, it will reduce the number of cases after 30 days by 96%.

And if it can be reduced by 60%, we will see exponential decay instead of exponential growth. (assuming R=2.4 is the average number of people each victim infects, which is a number I've seen used a lot).

It seems plausible that social distancing can reduce human contact for the average person by 50%, and for people with some flu symptoms by 80%. All this is to agree, the growth rate is by far the biggest factor in getting an estimate of peak impact.

Does anyone have insight into how moderate/voluntary vs. strict social distancing impacts the rate of spread? Anecdotally, the streets in the SF Richmond District feel a lot emptier than usual when I go out for walks/runs (pretty much the only reason I'm going out anymore). Seems like it could be up to a 50% reduction.

That should already be helping, but I wonder if spreading might follow a power law pattern where "super-spreaders" account for a vastly disproportionate share of transmissions. If that's the case, it might require a strict lockdown to meaningfully reduce the exponent?

All the bars and restaurants are still open, and people are still allowed to visit friends and family. Most nCoV transmission is in small groups with close contact, not stadiums. Closing offices and schools is a good first step, but as long as bars and restaurants are still open and food delivery services are carrying it all over town, it’s a drop in a bucket.

California just announced all bars are to close, and restaurants limited to half normal capacity.

> "Or, multiply it by less if you want to take into account various amounts of social distancing we're all doing. I'll cut that number above down by a huge amount – 90% – on the assumption that we all learn to stay home and self-isolate immediately, just to be super aggressive on my assumptions about how humanity will rise to the occasion"

Dropping 90% is not a great way to calculate this. Look at the math for 61 days out (from March 8): https://youtu.be/Kas0tIxDvrg?t=465

I don't think our social distancing and hand washing will be near enough to prevent millions of deaths, but it's important to recognize that a small change in the growth rate does make a huge difference.

Estimating how much we can affect the growth rate is hard, but I think models should be based on a iffy guess on that value rather than an iffy guess on the resulting count. (Expert models certainly are.)

Yep - the Bay Area actually has a great chance at curbing this because a larger fraction of workers than anywhere else can effectively work from home.