Medicine For People!

July 2020: Coronavirus Update

SARS-CoV-2 is the type of coronavirus that causes the disease we call COVID-19.


Here is your self-care update including a brief review of tests for the disease, including a test we offer at the office.

 

We do not detect everyone who has the disease

A study in Switzerland found about 12 people with antibodies to coronavirus for every person identified with the disease. Other studies find different numbers but the point is clear—there is some ten times more coronavirus out there than we are seeing. Routine physical distancing and masks reduce the risk of transmission from unexpected contacts and need to be part of your daily routine.

Indoor public places carry the highest risk

At this point, it appears that transmission occurs more often by inhalation of the virus from indoor air than it does by surface transmission. Outdoor transmission is rare.

Pay attention to the quality and fit of your mask

There are two reasons to wear a mask: to protect others from you, and to protect yourself from others.

The most effective masks are N95. Given the shortage of N95 masks, however, public health authorities reserve these for front-line health-care workers.

During this time of relative mask shortage, identifying a quality mask requires care. Effective masks have three to five layers and have minimal leakage around the edge of the mask. At the time of this writing, this mask on Amazon seems most likely to be of better quality than others I could find. I base this on:

  • the details in the reviews
  • these masks appear to cover the nose and mouth well
  • they are made of 5 layers of non-woven material

I have no way of knowing whether they actually meet the KN95 standard that the manufacturer claims. KN95 and N95 are slightly different standards but similar enough in these circumstances. The N95 masks we use at the office do not use ear loops, but rather use two elastic bands that go entirely around the head, holding the mask tightly to the face as in this image:

mask
Photo Credit: https://tmd.texas.gov/Data/Sites/1/media/tmd-missions/2020/covid19/texas-communities.jpg

Notice the tight fit on this Texas National Guardsman’s N95 mask. A tight-fitting 3 to 5 layer mask is most effective. Air coming around the edge of the mask is not filtered. So if you buy a mask with ear loops, you will probably find that the fit is better if you modify the elastic loops as shown here in the image above.

Masks matter

COVID-19 is an influenza-like illness. Hospital health care workers who wore two-layer cloth masks were thirteen times as likely to contract influenza-like illness than if they wore a three-layer medical mask made of non-woven material.

The New York Times illustrates various types of mask here.

So, if you find yourself in crowded indoor spaces, especially around people who are not wearing masks, consider up-grading to a mask that provides greater protection.

What can we learn from SARS and Ebola?

SARS and Ebola died out with careful quarantine, contact tracing, and isolation of cases. We are working to do the same with coronavirus. It can be done.

Natural Immunity

Your immune system has an immediate response element that we call innate immunity. This system usually fights off infection before it gets started, rather like the immigration agents at a national border. There is natural a back-up system which we call acquired or adaptive immunity. This three-minute video beautifully shows these systems at work. Both immunization and a successful response to an infection can cause our adaptive immune system to produce antibodies which often, but not always, protect against re-infection in the future.

Tests for SARS-CoV-2

PCR Test

Most of the testing for coronavirus uses a swab in the nose which detects genetic material from the virus. The test can pick up 94% of cases on the first day of symptoms, 67% of cases on day 10, and is less sensitive as time goes on. This is called the PCR test.

Antibody Test

Antibodies in the blood signal an immune response to the SARS-CoV-2 virus. These develop in over 99% of people with COVID-19.  The major role for this test at this time is to determine the true incidence of COVID-19 in various communities, as it picks up cases missed by the PCR test.

Update early December 2020:

Given the current level of coronavirus activity in Jefferson county, a positive result on this test is accurate about 90% of the time unless you have had symptoms strongly suggestive of COVID-19, in which case it can be over 95% accurate.  A negative result will be highly accurate.  If you wish this test, call us for a telephone interview so we can let you know if the test will be helpful to you or not.

Since we do not yet know how long or reliably these antibodies protect us from future infection, you cannot use this test in hopes of determining that you are immune to coronavirus.  Masking and distancing will remain critical to your good health.

 

 

Thanks to Jill Buhler Rienstra for timely editorial assistance.

Endnotes

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Medicine for People! is published by Douwe Rienstra, MD at Port Townsend, Washington.