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Contemplating Curves – Understand Virus Spread

understand virus spread

Without a vaccine, about two-thirds of us must catch COVID-19 before the pandemic ends. I wish the politicians and scientists would state facts like this. You need to understand virus spread.

Recently, I realized I had a lot of questions about virus spread, flattening curves, and infection dynamics. I dug into this, and concluded that our leaders and commentators were doing a poor job of explanation. Perhaps they did not understand it. Perhaps they were withholding information. Thinking you might be in the same boat of uncertainty as me, I am posting my best effort to understand virus spread. Here goes.

By definition, a virus is a parasite that needs a host to reproduce. We are these hosts for COVID-19. A virus will keep on infecting and reproducing (spreading) until there are no new hosts left. Basically, if I am a virus I will only stop spreading if everyone is protected by effective antibodies or vaccine.

All of our draconian isolation and hygiene measures are not stopping spread. Pardon the pun, but we are just spreading out the spread curve. So when the experts tell us we will be living with COVID-19 for two years, they are simply saying that we will take that long to reach say 70% of our population protected by antibodies or vaccine. We call this herd immunity, which means that enough of us have immunity to continuously lower the rate of transmission towards zero.

Without a vaccine, most parts of Canada and United States are maybe 10% towards herd immunity. New York City is a third of the way towards herd immunity. And Sweden, as of today, is around half-way to herd immunity.

If you study the chart above and do some mental calculus, you will see that the area under both red and blue curves is about the same.  This means that our “flattening the curve” (Blue) does not result in less COVID-19 cases. It simply means that these cases happen with a lower spike and over longer time. Either way, without vaccine, perhaps 60-70% of all Canadians and Americans will need to catch COVID-19 before our pandemic ends.

Understand Virus Spread – Curve Flattening Results

There’s an area under the Red Curve above that I marked with a star and labelled “without protective measures.” When we talk about “flattening the curve”, we are talking about ensuring that our hospitals always have room to treat another infected patient walking in the door during the peak.

Our math is fairly simple. Hospitalization rates for COVID-19 infected are about 5% for younger and 15-20% for older folks. These are the ratios driving those infected towards hospital. Once we admit people to hospital, we find mortality rates of around 5-10% of cases for younger and 40%+ of cases for older folks. These ratios drive death rates.

Would more lives have been lost without our lock-down? Hard to actually say. Please consider some facts and policy alternatives.

  • Many jurisdictions (provinces, states, hospital regions) saw no benefit from lock-down because their peak hospitalizations could have been met by existing capacity. In these jurisdictions, lock-down did not save lives.
  • Other jurisdictions were able to quickly boost their ICU capacity, and many could have done more if ventilators were more available. Sweden temporarily boosted ICU beds by 300%. New York temporarily added thousands of hospital beds, showing it could be done. Jurisdictions that temporarily increased capacity may not have needed to lock down. (New York City needed the lock-down, but likely not all other cities.)
  • Some countries, like Korea, were able to ramp up testing. If you can identify and isolate mild cases of COVID-19 within 24 hours, there is no need to lock-down. Recent modeling shows that even if only 25-30% of mild cases voluntarily self isolate quickly, we would not have needed lock-down to save lives. But that requires a commitment to testing.

So, in Canada and United States, it’s hard to evaluate the benefit of the lock-downs, other than at the extremes. Fact is, we just were not prepared and we panicked. While you contemplate this, you might watch this commentary Working Smarter, Not Harder.

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