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People tend to believe this virus is vastly more contagious than other airborne illnesses. It's certainly more contagious than the flu, by all accounts so far,

People tend to believe this virus is vastly more contagious than other airborne illnesses. It's certainly more contagious than the flu, by all accounts so far, but it's not even close to as contagious as measles. Simply walking by or standing next to an infected person almost certainly won't get you infected, unless they are actually coughing and sneezing in an indoor space (or directly at you).

ceejayoz 7y ago
To be clear, it's not airborne. Measles is so contagious because it's airborne; SARS-CoV-2 is spread via droplets that fall to the ground fairly rapidly. It's a technical distinction, but an important one. https://www.who.int/news-room/commentaries/detail/modes-of-transmission-of-virus-causing-covid-19-implications-for-ipc-precaution-recommendations https://www.who.int/news-room/commentaries/detail/modes-of-t... > In an analysis of 75,465 COVID-19 cases in China, airborne transmission was not reported. (This is also a reason masks can be effective despite the virus particles being smaller than what masks can stop; you don't have to stop the particles, but the much larger drops they're contained within.)
- dboreham 7y ago
  >To be clear, it's not airborne. I understand the distinction, but the terminology should be renamed imho, to something like "epidemiologist airborne". Because to the layperson it definitely is transmitted "through the air", implying again in everyday terms "airborne transmission". e.g. read this : https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article and look at the associated diagram: https://wwwnc.cdc.gov/eid/article/26/7/20-0764-f1 https://wwwnc.cdc.gov/eid/article/26/7/20-0764-f1 Those people were NOT all within six feet of each other. The German auto part plant paper also details transmission where nobody sneezed or coughed at a short business meeting.
  - ceejayoz 7y ago
    > Those people were NOT all within six feet of each other. As that study discusses, they were in the path of an air conditioner. The "six feet" thing is a rough estimate, not the Eleventh Commandment.
- tzs 7y ago
  Also, many filters actually can stop smaller particles than you might expect based on the rating. Most people think of a filter as working the way a net does. There is a gap size between the fibers, and anything smaller than that gets through easily, and anything larger does not. It's more complicated because there are actually 4 mechanisms that might stop a particle from getting through. 1. For particles bigger than the gaps, it does work like a net as most people expect. 2. For particular smaller than that but massive enough that they cannot change direction fast enough to follow the air stream they can miss turns of the air flow and get embedded in the fibers. 3. For even smaller particles they can get jostled around significantly by hits from gas molecules (like with Brownian motion). This can knock them into fibers where they can become embedded. 4. Some filters materials have an electrostatic effect that can attract and hold passing particles. One of the reasons filters are commonly rated by their efficiency at 0.3 micron is that this is in the region where the filter is least efficient. For bigger particles, the gains from #2 and later #1 more than make up for #3 being irrelevant at those sizes. For smaller particular, the gains from #3 increase efficiency. So you have the filter roughly getting worse down to the 0.3 micron ballpark, and then getting better as particles become still smaller, and at some point as you continue getting smaller it is going to get worse again. (I don't know where that final turn around is).

ceejayoz 7y ago

To be clear, it's not airborne. Measles is so contagious because it's airborne; SARS-CoV-2 is spread via droplets that fall to the ground fairly rapidly. It's a technical distinction, but an important one. https://www.who.int/news-room/commentaries/detail/modes-of-transmission-of-virus-causing-covid-19-implications-for-ipc-precaution-recommendations https://www.who.int/news-room/commentaries/detail/modes-of-t... > In an analysis of 75,465 COVID-19 cases in China, airborne transmission was not reported. (This is also a reason masks can be effective despite the virus particles being smaller than what masks can stop; you don't have to stop the particles, but the much larger drops they're contained within.)

dboreham 7y ago
>To be clear, it's not airborne. I understand the distinction, but the terminology should be renamed imho, to something like "epidemiologist airborne". Because to the layperson it definitely is transmitted "through the air", implying again in everyday terms "airborne transmission". e.g. read this : https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article and look at the associated diagram: https://wwwnc.cdc.gov/eid/article/26/7/20-0764-f1 https://wwwnc.cdc.gov/eid/article/26/7/20-0764-f1 Those people were NOT all within six feet of each other. The German auto part plant paper also details transmission where nobody sneezed or coughed at a short business meeting.
- ceejayoz 7y ago
  > Those people were NOT all within six feet of each other. As that study discusses, they were in the path of an air conditioner. The "six feet" thing is a rough estimate, not the Eleventh Commandment.
tzs 7y ago
Also, many filters actually can stop smaller particles than you might expect based on the rating. Most people think of a filter as working the way a net does. There is a gap size between the fibers, and anything smaller than that gets through easily, and anything larger does not. It's more complicated because there are actually 4 mechanisms that might stop a particle from getting through. 1. For particles bigger than the gaps, it does work like a net as most people expect. 2. For particular smaller than that but massive enough that they cannot change direction fast enough to follow the air stream they can miss turns of the air flow and get embedded in the fibers. 3. For even smaller particles they can get jostled around significantly by hits from gas molecules (like with Brownian motion). This can knock them into fibers where they can become embedded. 4. Some filters materials have an electrostatic effect that can attract and hold passing particles. One of the reasons filters are commonly rated by their efficiency at 0.3 micron is that this is in the region where the filter is least efficient. For bigger particles, the gains from #2 and later #1 more than make up for #3 being irrelevant at those sizes. For smaller particular, the gains from #3 increase efficiency. So you have the filter roughly getting worse down to the 0.3 micron ballpark, and then getting better as particles become still smaller, and at some point as you continue getting smaller it is going to get worse again. (I don't know where that final turn around is).