Wednesday, March 11, 2020

Exponential growth

Every health care provider that I know is receiving the same instructions:

Since test kits are in short supply, no one will be tested for coronavirus unless they have traveled out of the country in the past 14 days, or have been exposed to someone who has tested positive in the past 14 days.

What this means is that there are likely many people who have the virus that are not being tested because they have not traveled out of the country in the past two weeks. The big hole here is exposure.

Let's say that you just tested positive for COVID 19. Quick, name every person that has been within 6 feet of you in the past two weeks. How many people do you think you forgot, or don't know their identity?

I think there are far more cases than are being reported, simply because no one knows who they are.

Even so, the known cases are doubling every 2 to 3 days, and have been for the past 3 weeks. As I type this, there are 1,300 cases in the US. So, there were 328 more cases today, and 294 yesterday. That means the number of cases has doubled in the past 48 hours. At this rate, there will be 1800 cases by Thursday (tomorrow night) and 2500 by Friday. Another week, and there will be 12,000 cases by the following Friday. How long the cases can keep doubling is anyone's guess.

I am not an epidemiologist, but I do teach biology. When an organism is not being limited by availability of resources, we see exponential growth. Look at this chart, and it is a textbook case of an organism unlimited by access to resources:

Until COVID is cut off from the resources it needs, the growth pattern will continue.  Shutting down mass gatherings isn't going to do much. Most transmission is happening in small groups, not at sporting events. The way to curb this level of growth is to quarantine everyone. In a country like ours, I don't think that is possible.

Instead, this virus will continue, and with an R0 of more than two, it will continue to grow.

Trump cutting off trade with Europe won't accomplish much. The virus is already here.

Instead, we will ride this out as a nation, and we will see where it takes us. A vaccine is likely a year away.

1 comment:

Differ said...

UK BBC Today program had French govt minister responding to Trumps travel ban. Essentially said us public must do something to curb this mad president. BBC interviewer said perhaps the us govt should use 25th amendment to depose Trump. I didn't hear the same approbation about Italy closing its borders.