Case Update: April 27th, 2021; Indoor Transmission, New CDC Guidance

This is a case update. I’ll also talk about a new paper discussing indoor transmission as well as new CDC guidance.

This US is recovering from the 4th wave.  Yes, the wave was much smaller than others, and if you don’t want to call it a wave, I won’t argue with you.  Michigan bore the brunt of new cases, but cases are going down.  Only Washington, Oregon, and Colorado are still experiencing higher case loads.

Graph is by me, from data collected from Johns Hopkins University COVID site. Graph is presented in a logarithmic format to emphasize small numbers. Note that each number on the left is 10x higher than the one below it.
Endcoronavirus County Level Map, April 26th, 2021
Endcoronavirus State Level Map, April 27th, 2021

California and San Diego County continue to have fewer confirmed new cases.  In fact, California had just 661 new cases on Sunday.  The state hasn’t had fewer than 1000 new cases since almost exactly a year ago on April 28th. Yes, Sunday always has the fewest cases of the week, but it does indicate that cases are trending lower.

Graph is by me, from data collected from Johns Hopkins University COVID site. Graph is presented in a logarithmic format to emphasize small numbers. Note that each number on the left is 10x higher than the one below it.
Graph is by me, from data collected from San Diego County Public Health. See also regularly updated slides from SD County. Graph is presented in a logarithmic format to emphasize small numbers. Note that each number on the left is 10x higher than the one below it.
Graph is by me, from data collected from San Diego County Public Health. See also regularly updated slides from SD County. Graph is presented in a logarithmic format to emphasize small numbers. Note that each number on the left is 10x higher than the one below it.

Internationally, a large peak is starting to improve. India has been particularly hard hit by the current wave of cases.  The higher cases are likely impacted by the more infectious new variants as well as slower vaccination rates.

Graph is by me, from data collected from Johns Hopkins University COVID site.
Endcoronavirus Country Page, April 27th, 2021

Indoor transmission: Several news outlets have been talking about a new paper on indoor transmission of SARS-2 published by a lab at MIT.  It makes several interesting points.  First, the paper points out that the Six Foot Rule was designed to mediate infection from large droplets like we see for the flu.  Large droplets usually only travel from a person to the ground in 6 feet or less.  SARS-2 on the other hand, appears to be transmitted as small droplets in an aerosol.  The micro-drops stay in the air much longer and can travel much further.  Transmission in indoor settings are a function of the number of people in a space, and the time of exposure.  Ventilation helps reduce transmission.

MZ Bazant and JWM Bush, PNAS2021 Vol. 118 No. 17
MZ Bazant and JWM Bush, PNAS2021 Vol. 118 No. 17

The authors also point out that the likelihood of transmission outdoors is very low.  One paper they reference has data from 7,324 transmission events, only 1 happening outdoors.  They also say that masks have much more effectiveness in preventing transmission than lockdowns or social distancing, adding more evidence that the virus spreads as an aerosol.

Are you surprised by the papers conclusions? If you’ve been reading my posts, then probably not. I’ve been writing similar things since May 27th of last year. So why are people talking about this now? I certainly have my opinions, and I’ll bet some of you can guess.  Meanwhile, several news outlets are saying that the CDC is about to release new guidance that vaccinated individuals can now go outdoors without masks.  At the risk of running counter the CDC, I’ll just mention that I’ve been going outdoors without a mask since March of last year, at my most concerned. I almost always wear a mask indoors, but almost never wear a mask outdoors.

Don’t fear, but be smart,
Erik

1 thought on “Case Update: April 27th, 2021; Indoor Transmission, New CDC Guidance

  1. I know 2 people who got COVID 1 month after their second vaccine. A mother who is 98 and her grown son who lives with her in Las Vegas. The son had a mild case but mom got pretty sick. Not sick enough to go to the hospital.
    Mom never leaves home so it’s assumed that her son brought it home.

    My concern is that most people I know think after the second vaccine they are immune. The infection may be milder but we still don’t know the long term effects it takes on the body.
    Is there any data on this that you can comment on?
    Thank you

    Like

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