Pandemic Basics

[Dr. Borracho]

A differential calculus equation can be used to calculate the characteristics of a pandemic -- the speed with which it spreads, the number of people it will infect, its severity, etc. Without going into the complex equation, the key to understanding it is the R value. R can be thought of as the average number of people each infected person passes the disease on to. If a hundred carriers pass the disease to 200 people total, then R=2.0. If a hundred carriers only infect fifty other people, then R=0.5. If R is greater than 1.0, the disease will spread exponentially and become a full blown pandemic. If R is less than 1.0, the disease will reduce and, if you can reduce R to zero, the pandemic goes away completely. Consider polio and smallpox for which widespread vaccination reduced R to zero. Most diseases can be controlled, like the flu, but not eliminated. The way to halt a pandemic is to analyze all the factors affecting R and determine how to reduce them. Then you must act on those factors.

Imagine a man with a shotgun. R is the number of people he will be able to shoot. If he takes his shotgun to the Superbowl and fires randomly into the crowded stadium, he can hit a large number of people. Imagine that each person who gets hit by a pellet pulls out his shotgun and starts shooting. The chain of shooters expands and very quickly everybody is shooting and everybody is getting shot.

Now imagine a million anonymous shotgun wielding madmen wandering around America shooting people in public places and everybody who gets hit starts shooting at others. How do you protect yourself? Avoid public places, stay out of shotgun range from people you see, wear a bullet-proof vest, and call the police when you see a guy with a shotgun so they can arrest him. How do you avoid the pandemic? Avoid public places, stay out of range, wear a mask, and test people so you can identify carriers and isolate them.

With shotguns, there are dozens of factors that can affect the number of victims and severity of the wounds – the gauge of the shotgun, the choke, the pellet size, the number of pellets, the amount of gunpowder in the shell, etc. Likewise, with any pandemic, there are a plethora of factors affecting the spread of the disease. We still don’t even know the values of all of the factors influencing the nuevo corona virus, which causes Covid-19. But until the R value falls well below 1.0, to go unprotected to places where there are crowds of unmasked people is begging to catch the disease and take it home with you. Restrictions around the country are being lifted before the R value has been brought down to 1.0, which makes it inevitable that R will shoot right back up. That is compounded by the fact that a large percentage of the population refuses to avoid crowds or wear masks in the first place.

A great book for understanding pandemics is “Spillover” by David Quammen. It is comprehensive enough to cover most of the details of pandemics, but is not too technical for a layperson to understand. It is also informative in explaining how pandemics are investigated to determine disease factors and allow us to contain pandemics. It was published in 2013, before the nuevo corona virus outbreak began, but it warns throughout the book of TBO – The Big One that is coming, or I should say, was coming when the book was written. It also makes it clear that pandemics will always be with us. We have to be alert and prepared to minimize the effects without knowing ahead when to expect the next big one and we have to act immediately. For this pandemic, we were not prepared and we have not fully embraced the steps needed to control the disease.

New Zealand, population 4.8 million, is already Covid-19 free. They have defeated it. They stopped it with only 1,154 diagnosed cases and 22 deaths. They did that by having planned ahead, then immediately activating the plan. They banned crowds, required masks, and aggressively tested people to identify and quarantine carriers before they could spread the disease. Entry into New Zealand is extremely restricted from anywhere in the world until this is under control and a vaccine is available. Unfortunately, in the US we are not doing very well at any of those things.

If you would like to learn more about pandemics, "Spillover" is highly enlightening. Otherwise, avoid crowds and wear a mask when you're away from home. And avoid madmen with shotguns!

[orrb]

This is probably the best post I have ever read on this board. Thank you for the great analogy.

[Dr. Borracho]

Much appreciated, B. Orr. Much appreciated.