Tag Archives: Disease

Covid-19: Exponential Growth & Epidemics

Covid-19 virus image
A Covid-19, SARS-CoV2 CoronaVirus


Immunologically naive populations

“Viruses have been circulating around the globe for millennia. One family of viruses that have been circulating are referred to as Coronaviruses. About a quarter of common colds are caused by Coronaviruses. Our bodies form antibodies to foreign invaders such as bacteria or viruses. If we have antibodies from a previous exposure then we can rapidly ramp up the production of those antibodies if we are infected by that same virus at a later date. This is why you only get Chicken Pox and the Measles once. The first episode generates protective antibodies so you can’t get infected a second time. For other infections, previous exposures do not make you immune to future infections but it does make subsequent exposures milder.

COVID-19 is a severe respiratory illness caused by the virus named SARS-CoV2. It is a novel virus, which means that no one in the world has antibodies to it because no one has ever been infected by it before. As such, when the COVID-19 virus invades our body we do not have pre-existing antibodies. We do not have a template to utilize from a previous exposure to rapidly create a defense against the virus.

Exponential Spread

Exponential math is very hard to grasp. Every person with the COVID-19 virus infects approximately 2 people. Some less, some more. The doubling time that is widely quoted is 6 days. Some scientists are saying it may be as short as 2–3 days (unpublished first-hand information)! Let’s say the infection rate doubles every 6 days. That means that if 50,000 people have the virus today, then in 6 days 100,000 people will have it. In another 12 days it’s 400,000 and less than two weeks later it’s over a million people. We have 330 million people in the US. The experts expect that 40–70% of people will be infected. Exponential growth does not take that long to get to those scary high numbers. Every 6 days we delay the number of infections double. ” – Howard Luks, MD

Here’s a YouTube Video that does a great job of explaining Exponential Growth. It comes from the Animated Math folks at 3blue1brown