Why "Social Distancing" can help mitigate spread.

This was provided by a friend of mine. I have friends and family in the medical community, and they are providing very helpful information.

Hi everyone. As an epidemiologist, I know I've been running around saying every case prevented now is multiple cases prevented down the road, but I worry that there is a gulf of difference in understanding between those of us who understand exponential growth and those who don't. This isn't a linear function, meaning it doesn't increase at a steady speed.

Let me explain. We have 16 days to the end of the month. If the doubling rate is 3 days (one estimate), then preventing a case today is preventing 32 cases by the end of this month (2^5). When we extend time outward to the end of April, so 46 days from now (15 doubling periods), the exponent growth shows how much more stark the situation is. One case prevented today prevents 32,768 new cases by the end of April (2^15)! (Or, we can flip that and say a new case caused today would lead to an average of 32,768 new cases by the end of April!)

The other important factor is the doubling time. This is what we are trying to lengthen when we talk about "flattening the curve" or "reducing the R0, the basic reproduction number". If the doubling time is extended to say 9 days instead of 3, then we only have 5 doublings until the end of April. So each infection now results in an average of 32 infections by the end of April rather than 32,768. Still horrible, but so so so much better.

This is why the situation is so critical here, now that we know we haven't identified every case, traced all contacts, and isolated. Things are going to go really fast really quickly now, and every action right now makes an unbelievable huge difference. We need to flatten that curve and we do so by preventing every possible chance of infection.

Please act like lives depend on your actions, because they literally do. If you prevent one case now, and this prevents 32 cases in the next 16 days, one of which would have died, you have saved a life right there. It's the type of invisible heroism we need in public health. There will be no medal of honour, but you will have saved that life just the same and I for one offer you the Public Health Invisible Medal of Honour for each and every action you take!

I will add here that even if we lockdown now, we will still see an exponential increase for awhile (in addition to any increase in diagnosed cases corresponding to an increase in testing). The average time before symptoms appear is about 5 days, but it can range from a couple of days at the short end to about 14 at the long end. At that point, it is believed 99% of symptomatic cases will have shown symptoms. So, even if we could fully stop spread right now (which we can't), we will still see all those earlier infections developing into illness. So, don't think that the huge increases we will see this week mean our actions aren't helping, okay?!