COVID19 Testing Explained, COVID19 Risk in Rural America, US Numbers Continue to Rise

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[dropcap]“T[/dropcap]he US hit 4 million cases this week and 143K deaths. Every day, we’re adding 66K new covid patients – more than triple the number in early June. It’s a lot of new cases a day, but the possibly good news: the number of new positive tests a day stayed flat – the first time since June. I say possibly because this week the big labs reported long delays in tests results. Did new cases flatten – or are we just waiting for results? Or has the virus moved to rural places where people live too far from test sites.  

US hospitalizations have doubled from 28K in late June to 60K this week – the same number as the April peak. US daily deaths have risen 65% since early June, from 500/day to 834 deaths a day this week. Over the next weeks, we’ll see if deaths follow the spike in hospitalizations and continue to rise. 

Or if we’ve gotten better at treating patients. Florida, California, and Texas are all averaging over 10K new cases a day – and have about 10K patients in their hospitals. Arizona saw a modest slow down in rising cases, though their hospitals are still full with current patients.  The big states of course mask the per capita numbers.

Louisiana and Mississippi are in pain – seeing over 500 new cases per million people. Oklahoma, South Carolina, Tennessee, Georgia, Nevada, and Idaho are seeing the virus spread at the same rate as California.And within the states the virus is spread out from cities to rural areas with limited resources. In Texas, Hidalgo County saw so many deaths, the crematorium has a wait list and bodies are stored in refrigerated trucks.

Globally, the world hit 15 million cases and 620K deaths.

The US, Brazil, India, Russia, and South Africa continue to see spikes as the virus spreads quickly through South America, Eastern Europe, and South Asia.

Testing

Let’s compare the types of coronavirus tests available.

Right now there are three types of tests

1. PCR
2. Antigen
3. Antibody

The PCR test is the big one you need to know – it is the test that official case counts are based on, and the gold standard for diagnosing coronavirus.

The PCR test works by detecting viral genes. It is incredibly specific, meaning a positive result is almost always a true positive. However, it may miss some cases, depending on when and how the specimen is collected and transported.Even on the best day, the test will miss about one in every 5 cases.

Some employers require patients to have a negative test to return to work, but patients can have a positive PCR test long after their symptoms have resolved. Doctors agree that repeated PCR testing for a negative result should not be a requirement for returning to work.  A study from Korea found that COVID patients could test positive by PCR months after their diagnosis, but they found no evidence of live virus or viral transmission from these patients. This means that patients are shedding viral fragments that aren’t contagious.

Next, what about antigen tests?

Antigen tests detect viral proteins. The big advantage to these is the quick turnaround – these are “point of care” tests, meaning they can be performed in just a few minutes in a doctor’s office while you wait. So why aren’t we using these everywhere? The problem with antigen tests is that they are not very sensitive – they require 1000 times more virus than a PCR test.

In fact, one study found they were only 30% sensitive – meaning 70% of people with COVID had a false negative test. Because of these, the WHO does not recommend using antigen tests. If used, a PCR test should be performed any time an antigen test is performed to confirm the result.(2) Lastly, antibody testing (3). This is a blood test, and won’t be positive until 1-2 weeks after symptoms begin, so it is better for detecting whether a person has had the virus in the past. 

Now, the antibody test is the opposite of the PCR and antigen tests, in that it is sensitive, but not specific. This means that you can believe a negative result, but a positive result may be a false positive. 

So what should we expect going forward on testing? The recent case increases have caused delays in the reporting PCR tests, and some patients are waiting a week or longer for results. Scientists are working on finding a more sensitive rapid antigen test that can be used to quickly determine whether a patient has the virus. 

Antibody testing will continue to be used by epidemiologists and in some patients, but expect PCR to continue to be the gold standard for diagnostic testing until a better antigen test is developed. Antibody testing will continue to be used by epidemiologists and in some patients, but expect PCR to continue to be the gold standard for diagnostic testing until a better antigen test is developed.

NYC vs. RURAL

Although initially hit hard, NYC Covid cases are down, but as you can see in this graph cases have increased 2.5 x in the last month in the nonmetro US.

Why?  And what’s coming for the American countryside? 

I’ve worked in both NY during the surge, and rural California ERs diagnosing COVID19–let’s talk about it. As you can see in this graph, when Covid hit big cities like New York in April, viral spread was enhanced by population density–that’s this black box on the left–many people living in small area.  Now that population density benefits rural America because people live more spread out, you can see that black box on the right here, showing lowering risk. 

But look at what raises risk for small towns under 2500, and I mean raises the roof–age.  An older population.  (insert age stat). Remember most Covid deaths occur in people over 65, and rural America has more elderly than big cities, putting these small towns at risk. For places slightly less rural 2500-10,000, there is risk from age, but also poor health, things like heart and lung disease, cancer–but also, institutions, ie prisons. Nursing homes is the main risk for 10,000 to cities of 1,000,000–not as many in the smallest of towns.

Another study shows essentially the same thing–that the COVID19 risk of age and general health–is worse in rural America. Additionally, rural poverty leads to increased Diabetes, high blood pressure and obesity–all connected to worse Covid outcomes.  Decreased willingness to follow public health recommendations to social distance and wear masks makes rural prevention, and viral spread, an even greater challenge.

Outbreaks

Look at the non big city red hot spots on this map. 

What do we learn when we look at outbreaks?  Where do they come from?

Similar to the above data, we see 3 things:

1. Prison outbreaks
2. Meatpacking plants–both make sense, right?  People in close contact inside for long periods of time, limited ability to socially distance.
3. Number 3 is something we’ve talked about before on this show–race.  Note how many communities of the top 10 include high numbers of Latin American, African American and Native American populations.  Again, Covid affects us disproportionately by race in America.

In addition to the above, churches and grocery markets, places where people gather, appear to increase risk of spread.  You can imagine the public health challenge with 1 grocery store in 50 miles.  Additional causes for concern–rural hospitals are closing, and have fewer hospital beds and ICU beds, fewer specialty services, and lower testing and tracing capacity–all impacting their ability to prevent and treat this disease.

While NYC’s population density put it at risk–so many people living in one place–rural America is spread out comparatively, reducing the risk of viral spread. However, there are clusters of outbreak related to density just the same–in meat packing plants and prisons, churches and grocery markets–places where people come together still brings risk of infection.  Over 65, and medical conditions 80% of deaths–more of this rural USA.

Rural invisible, false sense of rural immunity.  

In big cities, Covid risk includes population density, generations of families living together, essential workers using public transportation, and of course increased risk with race, diabetes, obesity, high blood pressure, age and obesity. Rurally, density a factor, from work–think prisons and meat packing–although people live farther apart. 

We’ve talked before about race and Covid–those disparities still hold true in Rural America, even though 80% white vs 56% of cities. Most of the counties with the highest levels of Covid have large populations of African, Latin and Native American populations–these disparities still exist in rural america. But there’s also an income story that affects all groups.

Greater levels of poverty in rural America, which leads to higher levels of DM and HTN, which we know is a risk factor for bad outcomes with COVID. 

References:

1. https://ourworldindata.org/covid-cases
2. https://covidtracking.com/data
3. https://abcnews.go.com/Health/quest-labcorp-warn-coronavirus-testing-delays-demand-surges/story?id=71555595
4. https://apnews.com/2c48b10419a28caec8012b0c65244424
5. https://covidtracking.com/data
6. https://coronavirus.jhu.edu/data/new-cases-50-states
7. https://www.chron.com/local/article/Texas-county-forced-to-store-bodies-in-trucks-as-15428456.php
8. https://www.reuters.com/article/us-health-coronavirus-usa-idUSKCN24N2F2
9. https://www.worldometers.info/coronavirus/
10. https://ourworldindata.org/coronavirus
11. https://www.fda.gov/consumers/consumer-updates/coronavirus-testing-basics
12. https://www.aruplab.com/news/4-21-2020/How-Accurate-Are-COVID-19-Tests
13. https://www.acc.org/latest-in-cardiology/journal-scans/2020/05/18/13/42/http%3a%2f%2fwww.acc.org%2flatest-in-cardiology%2fjournal-scans%2f2020%2f05%2f18%2f13%2f42%2fvariation-in-false-negative-rate-of-reverse
14. https://fox17.com/news/local/vanderbilt-doctor-stop-using-covid-test-to-confirm-recovery-from-the-virus
15. http://www.cdc.go.kr/
16. https://www.fda.gov/consumers/consumer-updates/coronavirus-testing-basics
17. https://www.sciencedirect.com/science/article/pii/S1386653220302420
18. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240272/
19. https://www.who.int/news-room/commentaries/detail/advice-on-the-use-of-point-of-care-immunodiagnostic-tests-for-covid-19
20. https://www.medrxiv.org/content/10.1101/2020.06.04.20122358v1.full.pdf
21. https://www.cnbc.com/2020/07/13/us-coronavirus-surge-leads-to-testing-delays-across-the-nation-quest-diagnostics-says.html

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