This Covid update is more  optimistic than past updates.  The data is changing rapidly and this will change the outlook and recommendations as they become outdated.  Today, I am going to discuss how some studies are suggesting that SARS CoV 2 is much more wide spread than we realized which implies a much lower fatality rate. I also want to share information on antibody testing including, which tests are good and the importance of choosing an accurate test.  

The below graphic is a slide I prepared for a few decision makers on 4/26/20. It evaluates case hospitalization and case fatality rates in LA County vs potential infection hospitalization and fatality rates in LA County.  The difference between case and infection rates are based on studies using antibody testing. The chart and graph evaluate the number of hospitalizations and deaths as of 4/26 relative to the  potential infections based on the multiples from the NY data and the USC study.​

​In New York City, the rate of cases vs infections presented by Gov. Cuomo was approximately a multiple of 12, suggesting a much lower infection fatality rate. In Los Angeles, USC completed a study using antibody testing suggesting the we had 28-55 times more infections that cases reported. These are in-line with the Stanford/ Santa Clara study suggesting they had 50X more infections that cases reported. All of these studies optimistically show a much lower hospitalization and fatality rate.  Having said that, there are problems with the antibody tests, so we need to evaluate these tests and studies with some healthy skepticism. 

For my patients, I am offering the Quest RT-PCR for active symptoms and the Abbott serology test to evaluate prior exposure.  The Abbott serology test has been tested internally at Abbott and through a separate commercial lab. From internal testing Abbott reports a sensitivity of 100% and a specificity of 99.5%.  The outside lab validated the prior testing suggesting a sensitivity of 100% and a specificity of 99.4%. When evaluating antibody tests, the accuracy is very important as many of these tests are not very accurate.  The specificity of these tests is the more important parameter, as you want as few false positives as possible.

If you are not a patient of mine, but are interested in antibody testing, the FDA has given letters of authorization to some companies.  Click here for a complete list.  [https://www.fda.gov/medical-devices/emergency-situations-medical-devices/emergency-use-authorizations#covid19ivd]

With any of the tests, they should be done in conjunction with a conversation with your doctor.  The antibodies show past exposure.  The antibody seems to offer a window of protection, though there are questions related to seroconversion and the permanence of immunity after developing antibodies.

On a separate note, I wanted to include some educational links to excellent talks on SARS-CoV-2.

The first is by Dr. Olsterholm from the MN Center of Infectious Disease Research and Policy (CIDRAP)  He has 5 excellent podcasts thus far and many webinars available at this site. https://www.cidrap.umn.edu/covid-19/podcasts-webinars

The second excellent educational talk on SARS-CoV-2 is by Dr. Pamela Bjorkman a Cal-tech professor whose lab is currently evaluating the virus.  https://www.youtube.com/watch?v=OBcc_dk9Q9U

Be well,


Amy

Let’s start with good news. In California, we have definitely “flattened the curve.” We are approximately 90% below my projections from the LAC data from 3/22 and 3/28. Our doubling time has significantly increased, and we are off our exponential curve.

I have been postponing putting out this aspect of my analysis for a week now. Everyday things seem to change, and I hoped my analysis would lead me elsewhere.  I want to spend a minute discussing what flattening the curve means,  what different aspects of the curve means and why I think we will have periods of self isolation/ social distancing and re-socialization over at least the next year.

The curve represents cases over time. The area under the curve represents the total number of cases.  By flattening the curve, we prevent hospitals from being overwhelmed. But it doesn’t mean we ”eradicate” the disease. We live in a globalized society where international travel still occurs and people can travel state to state.  If we don’t want to overwhelm the medical system and the number are correct, flattening the curve means we push out our time-line. It means this ends by one of three ways, we have a vaccine, we have an effective treatment or we reach herd immunity (which is thought to occur when about 2/3’s of the population has had the disease). 

Herd immunity, assuming the numbers are correct is several years away.  I think we will have a vaccine or treatment first.  So what does this mean?  I think it means we will go through multiple periods of social-distancing/ self isolation and re-socialization.  I’m hoping our numbers are wrong and that we are significantly underestimating the number of cases we have had. There are two main factors that give me hope.   In Iceland, half the people that have tested positive were asymptomatic and if Covid began in China in November and it has the transmissibility that it seems to have, hopefully many more people have had it than have realized it.
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Let's walk through a scenario below of how LA County could reach herd immunity without overwhelming the system, and you will see why I think we will have a vaccine or treatment before herd immunity and why this won't be over in a few months, but we will likely see multiple cycles of social distancing and re-socialization.  

We know that LA County has 10.1M people this means we need about 6.7M cases of covid to reach herd immunity. If we assume 5% of cases need a ventilator that means we will have 336,602. people needing a vent.  Average duration on vent has been variable depending on data-sets, but let's assume the average person who needs a vent requires it for 12 days. 336,602 x 12 is about 4M vent days required.  Gov. Newsom has called for 10,000 vents in CA, that means we should have about 2500 in the LA area.  If we divide 4M vent days by 2500 vents we will get the number of days required to reach herd immunity without overwhelming the system.  The answer is about 4 years.  That assumes we have our numbers of cases correct, which is a big if.  Harvard public health came out yesterday suggesting a similar scenario, though I am sure they had a much more eloquent model.  What this means if these numbers hold is that we have a long winter ahead, but with social distancing, we can prevent the system from being overwhelmed.

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Be well,

Amy