A good review is here of what airborne transmission of a pathogen actually means. (AT Paper) The paper is long, but not terribly technical and it does help you understand that various methods by which the virus comes in and goes out of the respiratory system and whether masks could actually make any difference. It also helps understand the difference between droplet and aerosol production and dynamics. It would be very helpful to have more actual research on what is expelled–form and amounts–by asymptomatic but infected persons, those with mild or moderate symptoms and those with severe illness.
And this paper is a more technical assessment of airborne transmission. (Medrxiv Paper) This goes back to the notion of droplets versus aerosols. Aerosols stay suspended and can travel in air, droplets, well, drop. Scientists are fiercely debating whether this virus is airborne and if so, to what extent. Sneezing, coughing, breathing and speaking were compared for production of aerosols and estimated virus concentration. The exhalation was assumed to take place in unventilated indoor space and other individuals who might inhale were assumed to be in that space. Although it takes a while to figure it out, this was not an actual experiment, but another modeling exercise. As you might expect, coughing produced the most aerosols, followed by sneezing, speaking and breathing. The authors believe aerosols are definitely produced, some with enough virus for infection if inhaled, although generally concentrations were low. The authors conclude that aerosol transmission is possible, but more study, i.e., a real experiment, is needed. Doesn’t do much to answer the question.
Here is an interesting depiction of mobility changes by state. (Mob. Data) You can see that while the pattern is similar, there is substantial variation by state. For those who think Arizona never experienced a hard lockdown, think again. And for those who think you have to mandate this stuff, even in places without lockdowns, people voluntarily limited their activities. And look at the depth of the shutdown in New York, Massachusetts, New Jersey, Pennsylvania. Didn’t stop those places from having the worst death rates in the country. Maybe has something to do with the primacy of indoor transmission.
Haven’t talked about Sweden in a while, and the doomsayers aren’t either. Look at Worldometers (WM Site) coronavirus data, go to the list of countries, click on Sweden and then look at the daily cases and deaths charts. A complete disaster, right? Cases spiked somewhat as testing expanded, but deaths are on a steady downward trend and low. The epidemic is clearly basically over there, with far fewer restrictions, little mask-wearing, schools open, etc. Death is far lower than a number of US states. And while, as expected in a global economy, there some been some decline in employment and activity, compared to Europe or even the US, Sweden is in much better shape. And Sweden, I believe, is done with serious coronavirus problems, whereas its neighbors are going to be dealing with cases for a longer time and will likely end up in a similar place. This article gives more of a review on Sweden. (Sweden Article)
I have basically given up on modeling papers, both of the epidemic and of the effect of mitigation measures, because the designs and methods are all basically worthless and tend to reflect the authors’ biases, rather than any attempt to ascertain truth. This paper is an example, but is a little better in approach. (Medrxiv Paper) The researchers attempted to disentangle the impacts of relying on voluntary individual actions to mitigate spread versus mandated government policies. They conclude that while individual efforts have value, mandated lockdowns are 50% more effective in preventing cases. Interestingly, they find no value to mask mandates in reducing transmission.
Given the impressive skewing of coronavirus disease severity and death toward the old, they must be much more fearful of the virus, right? Wrong, according to a study from the National Bureau of Economic Research. (NBER Paper) 1500 Americans were surveyed in the middle of May, near the end of the peak of the epidemic. The sample was drawn to be demographically representative. Respondents also had to answer some questions to demonstrate basic ability to understand the math of risk, so might have been hard to get a panel. Surprisingly in one way, but maybe not considering other indicators of the mental fragility of some of our younger generations, young people, who generally have very small risk, have greatly exaggerated perceptions of risk. These people must be completely incapable of doing even the most basic research about the epidemic, as they have expectations for hospitalization or death that are 100s of times greater than reality. Meanwhile, the older group has a lower expectation than reality, but also much lower than what the youngest group expects. What the hell are we teaching young people? Clearly not math skills, not critical reasoning skills, not the ability to go find data, when it has never been easier to find. It’s disgraceful to see such ignorance.