Three months ago the disease reached Kern County. At the time it looked like Kern County, and by extension California, had Covid-19 under control: 200 cases and only two deaths.
In contrast Madison County, Indiana, where I was raised, had 100 cases with nine deaths with only one-eight the population of Kern County.
Three months of a disease with an exponential growth rate is a lifetime. My oh my how things have changed. Today the front-page news in the Bakersfield Californian is that one of the three hospital systems here has again stopped elective surgeries. The others will likely do the same shortly.
Note: This is the second in a series on Covid-19.
Obviously, this isn’t a good sign. Elective surgeries are where hospitals in the USA make their money. The hospitals here quickly resumed elective surgeries as soon as the Governor permitted it. They don’t want to keep beds open for pandemic victims if they don’t have to. As of 6 July Covid-19 patients needed nearly 50% of the beds available in ICU here. The hospitals must fear that with rising infections they will need more beds–and staff.
Bending the Curve
While Kern County hasn’t “bent the curve” of rising infections, Madison County, Indiana has.
Let’s take look at Indiana first. In the chart below the number of total cases in Madison County has nearly leveled off. This is good.
Now, let’s take a look at Kern County. The number of cumulative cases here continues to rise. Not so good. The 7-day average of new cases here was hovering around 150 per day. With a total of more than 5,000 cases that’s a growth rate of 2%. What that means is that the total number of cases will double every month. By this time in August we’ll have 10,000 cases. If everything else stays the same, ICU beds in Bakersfield will be full by August. Public Health officials, of course, want to change the disease’s trajectory.
The infection rate in Kern County per 100,000 residents now exceeds that in Madison County, a one-time infection hotspot in central Indiana. Nevertheless, the death rate here is almost one-tenth that of Madison County. That could change. The pandemic is fluid.
Covid-19 hit Madison County’s care homes early–and hard. The disease has hit three care homes in Kern County too but the state quickly stepped in, keeping the death rate low. Subsequently, care homes here are tightly locked down and we haven’t seen any new outbreaks.
Kern County is also testing a lot of people, as is the state.
Why Covid-19 Growth Rates Matter
An infectious disease, such as Covid-19, grows exponentially. We have a difficult time visualizing this. For those of us who’ve studied biology or environmental science, we’re familiar with the story of the lily pond and the effects of doubling each generation and how quickly the doublings overtake the pond.
It’s the same with an infectious disease. A few cases may look harmless, but after a few doublings, the number of cases overwhelms our ability to care for the sick. This is the rationale behind the lockdowns and quarantines.
Everyone who’s invested in real estate or the stock market understands the “rule of 70” and doubling times. When you divide 70 by the interest rate or the growth rate of a stock, you will find the number of years it will take for your investment to double. Bankers, stockbrokers, engineers, and epidemiologists can do this calculation in their heads–they don’t even need a napkin.
For example, if Covid-19 is growing at 7% per day, it will double about every 10 days. Similarly, if the disease is growing at 15% per day, the number of cases will double about every 5 days. While this is bad, it can be a lot worse.
If you look at the charts plotting the progress of the disease you’ll often see a hypothetical curve labeled 1.35 for the daily growth rate of new cases. This means that the daily case number increases by 35%. The number may seem innocuous, but the effect is not.
This curve on the chart is a warning: Don’t go here, for here be demons. Growth at 35% per day produces a doubling almost every two days! And therein lays the power of exponential growth. Within 30 days of the onset of the first case, there will be 8,000 cases to care for.
USA Covid-19 Case Doubling
By now everyone has seen the chart of new cases per day in the USA. The chart has two humps or rising slopes. This isn’t what you want and it’s certainly not what we’ve seen in Europe or New Zealand where new cases are declining.
The 7-day average of new cases over the past ten days is growing at 5% per day across the country. At this rate, new cases will double every two weeks. We currently see about 50,000 new cases per day. If we don’t get a handle on the rate of infection, we’ll see 100,000 new cases by the end of the month. And remember, if we don’t lower the infection rate, we will double that by mid-August and by September we’ll be seeing infection rates of 200,000 per day.
This is what the steep trajectory of the curve means and why we have to “bend the curve.”
The good news is that we’ve dropped the mortality rate from a high of 8% to about 1% nationwide. Why isn’t clear, but we are getting better at treating those with the disease.
Without a change of course, the USA could be seeing 1,000 deaths per day by mid August and 2,000 by September. That’s 30,000 to 60,000 more deaths per month by this fall.
The mortality rate is widely divergent across the country. Indiana has twice the mortality rate of California and Pennsylvania’s mortality rate is three times that of the Golden State.
Infection Hot Spots
Southern and western states are seeing a growing outbreak of new infections. On 5 July Arizona’s rate of 495 new cases per million people rivaled that of New York State at its peak of 509 new cases per million people (7-day average).
Florida is not far behind Arizona and South Carolina’s case load is ramping up as well. Texas leads California’s growing number of cases per million people but not by much. California has been forced to closed bars and indoor dining again and has ordered masks when in public where social distancing isn’t possible.
In contrast, the Indiana and Pennsylvania infection rate has fallen substantially from the early days of the pandemic and are now a fraction of that of California.
Arizona’s infection rate is almost ten times greater than that in Pennsylvania.
Where are we headed? No one knows. Today’s news accounts included reports of dwindling supplies of PPE (Personal Protective Equipment). Not again, one may reasonably ask.
At least the exponential growth of the disease appears to have finally got the attention of those politicians who buried their heads in the sand for far too long. Wishful thinking is no treatment for a deadly virus.
With collective action on a national scale, effective treatment, and a bit of luck we might keep the total number of deaths below a quarter million Americans by the end of the year.
It’s Here: Covid-19 Reaches Kern County