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What is the positivity rate in south carolina - what is the positivity rate in south carolina- What is the positivity rate in south carolina - what is the positivity rate in south carolina
As states have reopened, the media has watched carefully for evidence of a "surge". If an area increases testing two-fold, even if the daily cases are stable, one might expect a doubling in daily case counts. This is the argument used by the president and governors in Texas, Florida and other places in trying to downplay upticks in cases.
They are correct that we must look not only at cases but also the testing rate to accurately assess whether a case increase is actually evidence of a viral surge, but are extremely misguided in downplaying the current undeniable surge happening in Arizona, Texas, Florida, and South Carolina.
The growth in cases is far far beyond the increase in testing, and this can be seen by the testing positivity rate. The testing positivity rate is simply the proportion of SARS-CoV-2 viral tests that come up positive in a given place for a given time period.
We include this in our web app developed by my PhD student Emma Zohner that allows the user to simultaneously look at testing, cases, deaths for different states and counties, but when it comes to following the test positivity rate plotted along with cases, I like the interface on the Johns Hopkins site even better. So why is this value important, and what does it tell us?
There are two key valuable insights we can gain from looking at the testing positivity rate for a country, state, or county:. Assess testing adequacy: When tests are scarce they are typically reserved for those with more severe symptoms, and leading to high testing positivity rates. Conversely, in regions where community testing is broadly practiced or ample supply is available for all who want to be tested, the testing positivity rate is lower.
Consistently high testing positivity over time potentially indicates that locale is under testing. Note that it is likely that actual new daily infections are about 10x the official case counts , so cases are just the tip of the infection iceberg , and undertesting suggests an even smaller part of the iceberg is showing. Assessing potential surges: If test positivity increases over time, this potentially indicates an uptick of infections in that location, and if it sharply increases, it may indicate a major surge.
If an increase of cases is simply due to increased testing, we would expect the testing positivity rate to remain stable or even decrease -- a sharp increase in testing positivity is one of the best indicators of an emerging surge.
Let's look at the 4 states that are undeniably surging right now:. These are staggeringly high positivity rates. With Texas, we also see a clear increase from test positivity from 4. If the governor made that point at the end of May, I would have agreed with him. However, the surge in testing positivity rate from 2. And these rates may be even higher in some of the most affected cities. South Carolina:. This is the quietest surging state because it has much smaller populations, but its per capita growth is on par or higher than the other three.
Other States:. Looking carefully at these plots, you can see that the increase in testing positivity is a potentially useful harbinger of an uptick or surge of cases. Indeed, it may be one of the key influential measures in the PolicyLab projection model that successfully predicted the Texas and Florida surges. So are there other states primed to surge like these 4? Let's look at some of the states that show evidence of increasing test positivity rate:.
The two states that jump out when you look at test positivity rate are Nevada and Utah:. Nevada, Utah and Idaho and Oregon :. Nevada seems prone to be the next surging location. Here I show neighboring Idaho, with low counts but test positivity rate increasing from 2. Hurricane Alley:. Bears close watching.
Other Southern States. Georgia, Alabama, and North Carolina are some other southern states worth watching. Northeast and Midwest :. What about California? I'll finish by saying some words about California. I've seen some commentators lump California in with Texas, Arizona and Florida as states with increasing covid numbers. I've considered it more in the "stable" category, as their testing rates have increased proportionally to their new daily case counts.
This is evident in the stable test positivity rate since April. There may be evidence of a slight uptick in the past couple weeks from 4. How durable is immune protection vs. Jeffrey Morris. What is Test Positivity Rate, why is it important, and what can we learn from it? Recent Posts See All. Post not marked as liked 3. Post not marked as liked Post not marked as liked 7.
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