Coronavirus #2 of 5: How widely will this spread?

Updated: May 26

This is the second in a series of blog posts about the coronavirus.

There is no "spin" in science. So welcome to the no politician zone. My promise to you is that I will quote and cite the best medical journals in the world (Lancet, JAMA and the New England Journal of Medicine) and the World Health Organization. If I have to quote the media, it will be clearly stated.

Disease Spread

When you talk about infectious disease spread you typically consider three factors:

1. The government’s ability to isolate symptomatic individuals,

2. The government’s ability to trace and quarantine others that have had contact with infected individuals, and

3. How transmissible/contagious the disease is.

Note: these are just contributing factors to how widely the disease spreads. I’ll address the disease’s severity in a later post.

Thoughts on factor #1:

This virus came from China; 63% of confirmed cases are still Chinese so the public health authorities are making assumptions based on their data which may or may not be accurate. (That stat is from the Johns Hopkins Covid-19 Tracker on 3/12/20).

It’s easy to isolate people in China where freedoms are legally and culturally limited ... you do what you're told to do over there. Go to Tibet for a couple of weeks as I did and you’ll see what I mean. (This assumption was recently confirmed by a WHO official who was on the ground in China).

We likely haven’t done a good job isolating people here in the United States because authorities rely on people to self-police. Those with symptoms after getting off of a flight from China were generally told to go home and not contact any one for 14 days. I can’t imagine that has happened here because we value individual liberty. If you’re a busy professional and you don’t have any symptoms but some health official told you to stay home, are you going to? Probably not. If you live paycheck to paycheck and need to get to your job to feed your family and you don’t have any symptoms but some health official told you to stay home, are you going to? Probably not.

It's tempting to think that our health system is better prepared than China for this. I’m sure that we have better technology. I’m sure that our doctors and nurses are better educated than theirs are. But the benefits may stop there. In order to isolate someone, you have to know that they are sick in the first place. We didn’t have our ducks in a row when this outbreak began. According to Reuters, the initial batch of CDC testing kits weren’t functional and we didn’t buy the German’s version. We elected instead to wait until we produced functional ones of our own. That decision delayed mass testing, so we still may have tens of thousands of cases that haven’t been diagnosed yet. South Korea’s seemingly excellent response required testing 10,000 people or more per day.

Thoughts on #2:

There are two big issues that affect our ability to trace people who have had contact.

First is the incubation period. That's the amount of time between getting the virus and showing signs and symptoms, which, in this case, is between 1 and 14 days, according to WHO. It averages five days.

For comparison’s sake, the seasonal flu incubation ranges between 1 and 4 days but averages only 2. So with the seasonal flu, you know pretty quickly when you are sick and can therefore stay away from people. That’s not the case with coronavirus. For this virus, the government has to trace and quarantine everyone that the affected patient has been close to in the preceding TWO WEEKS.

It’s impossible to do that for a lot of people. Scientists do not yet know when the infectious period begins. In other words, if a patient acquired the virus on February 9th and didn’t show symptoms until February 14th, was he contagious on February 10th or Feburary 13th? We don’t know yet. Regardless, because the incubation period is two weeks long, they would try to go back and test every person that the patient had been around between February 1st and February 14th. You can imagine how hard this, especially for particularly social people or those who travel for work.

Second, we have to consider how long the person is sick. It seems that the patient is most contagious when the disease is most severe. In China, hospitalized patients did not go to the hospital until between the 9th and 12th day after symptoms arrived. So, they were sick for a considerable time before needing urgent medical care. Contrast that with the flu. Typically, you’re sick (and mostly contagious) for two or three days and that’s it. Here, with the coronavirus, it seems to move slowly, again giving patients more opportunity to spread the virus.

Thoughts on #3:

So how contagious and spreadable is it? I’ll go straight to one of the pre-eminent infectious disease experts for an answer:

“Given the efficiency of transmission as indicated in the current report, we should be prepared for Covid-19 to gain a foothold throughout the world, including in the United States.”

--Anthony Fauci, MD, Director of the National Institute of Allergy and Infectious Diseases

Without saying it, Dr. Fauci is heavily implying that this epidemic will become a pandemic. (Epidemics are typically limited to certain geographies, while pandemics spare no regions of the globe). That might be satisfying enough for you … but if you’d like some more detail on how quickly it spreads, read on.

R-Naught: A Simple Lesson For A Simple Statistic

Please excuse the simplicity of the rest of this post; I'm still a science teacher at heart!

Let's say you're the coolest kid in school. You have a dollar bill in your pocket and there are two really rich kids who are competing for your friendship—Florence and Corey.

Florence says, "I'll multiply your dollar bill by 1.2 today and the new total by 1.2 (once per day) for the next 30 days. You keep every penny." You take her up on it ...

On day 1 you gain $1.20 ($1 x 1.2) more and now have $2.20 total. On day 2 you gain $1.44 ($1.20 x 1.2) more and now have $3.64 total.

On day 3 you gain $1.73 ($1.44 x 1.2) more and now have $5.37 total.

And this goes on for 30 days.

Then this other much richer kid, Corey, comes around says, "Pssssh. ONE POINT TWO?! That's weak. I'll make the multiplier TWO POINT TWO! Same game."

On day 1 you gain $2.20 ($1 x 2.2) more and now have $3.20 total. On day 2 you gain $4.84 ($2.20 x 2.2) more and now have $7.04 total.

On day 3 you gain $10.65 ($4.84 x 2.2) more and now have $15.49 total. You notice that this is, of course, growing much faster than Florence’s offer.

After 30 days, with Florence (who multiplied by 1.2), you amass $1,181.88. Amazing!

After 30 days, with Corey (who multiplied by 2.2), you amass 12.39 BILLION DOLLARS. Jackpot!

This math seems unreal. But try doing day 4, 5 and 6 on your own and you’ll see what happens. Or get your accountant to put it all into excel, and you’ll see.

So what the heck does this have to do with the coronavirus spread???

Florence is the Flu.

Corey is the Coronavirus.

The multiples of 1.2 and 2.2 represent the basic reproduction factor, also known as R-naught.

R-naught is the average number of people that the average infected patient will transmit his/her virus to.

The Flu has an R-naught of 1.2. The average flu patient gives the virus to 1.2 people. After 30 cycles of this process, the flu infects 1,181 people.

The New England Journal of Medicine just published on March 4th that they've honed in on 2.2 for the Coronavirus R-naught. (The Lancet says it's 2.5 which would be worse). That is, the average coronavirus patient gives the virus to 2.2 people. After 30 cycles the Coronavirus gets to 12.39 billion people—far more than there are people on earth.

I’ll provide you with some good news on these stats in the next post.


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