5 ms·

Interesting, they state the conclusion that "both surgical and cotton masks seem to be ineffective in preventing the dissemination of SARS–CoV-2 from the coughs

• belorn 6y ago
  > I would think that masks can have a positive impact even if they aren't perfect filters. That is when behavior comes in. If people are more likely to ignore social distancing if they wear a mask then you might get the opposite effect, as social distancing is seen as better protective measure than masks. This is one of the reasons why the health department in my nation only recommend masks for risk groups, like if you are working with elderly people.
  • em500 6y ago
    This is a completely speculative conjecture known as risk compensation (https://en.wikipedia.org/wiki/Risk_compensation https://en.wikipedia.org/wiki/Risk_compensation). It's often brought up in opposition of mandatory safety measures (quite prominently around seat belt legislation in the 1970s), but AFAIK it's never been shown to be numerically significant.
    • 9nGQluzmnq3M 6y ago
      Risk compensation, as in the idea that people are more conservative when they feel more at risk, is pretty well founded. It's risk homeostasis, namely the idea that people will voluntarily increase their risk until a target level is reached, that's controversial: https://en.wikipedia.org/wiki/Risk_compensation#Risk_homeostasis https://en.wikipedia.org/wiki/Risk_compensation#Risk_homeost... I recall reading some interesting research on this when it comes to playgrounds: these days unforgiving concrete is being replaced with bouncy rubber, and the compensation/homeostasis theory is that kids are playing in riskier ways because small tumbles don't hurt them any more.
    • watwut 6y ago
      It was suspect with bicycle helmets. But alternative hypothesis is that if helmets are mandated, people dont use bikes as much for transportation or causual pleasure rides, biking only for serious sport (making incidents go up per ride).
    • belorn 6y ago
      The people responsible at the health department could be wrong, as they are just employees, and could be misinformed/ill-trained. It is a speculative theory, and the official statement empathize that the singular most important thing people should do is is to stay at home if they are sick. The medical benefits of mask for people without symptoms is not clear (but I would be interesting to read research if someone can link that), and there is a supply demand right now to get mask to those groups that really need them. It is not a black and white issue of seat belt where there is ample proven evidence that in basically any car crash a seat belt is better than no seat belt. There is no shortage of seat belts, nor has there ever been one. The focus of car safety has also primarily focused on speed, where the survivable limit goes up if the driver has a seat belt, but even that higher limit is still much lower than the speed of many drivers. Thus the message there is to inform drivers the importance of both the benefit of seat belts, but also the critical message that speed more or less determine if a person is going to live or die. Even if people would risk compensate and go from the survivable speed without seat belt and increase their speed to survivable speed with seat belt, it would still be lower than what many people already drive their cars at. The worst case scenario of seat belts would thus be an improvement. We can not say the same thing about social distancing, where going out sick with a mask on is still a very bad idea. Thus the recommendation from the health department is right now that masks should go to those in risk groups and people who are sick should stay home. If research later show that people without symptoms reduces risk of infecting others by wearing a medical mask, and the supply of masks increases, then they will likely change their recommendation based on the changed situation and facts. (Small meta comment, but it is interesting how skeptical people are of the medical department that is responsible for handling the pandemic. It is true that critical questioning any government recommendation is useful, but maybe a bit more open minded discussion would be better).
• em500 6y ago
  Indeed, the actual numerical results in the article table shows that masks are very effective, so it's puzzling where their narrative conclusions came from.
  • bcoates 6y ago
    A log-reduction of around 0.5 isn't much. "very effective" would be like 3-4 which even this n=4 study is enough to rule out
    • em500 6y ago
      0.5 log-load reduction is a 66% decrease. A 1.5 reduction is 96%, which is N95 standard. Starting from 2.56, a log reduction of 3-4 is impossible. In any case, the large number of NDs (not detected) everywhere in the table, but especially inside the masks after the patient just coughed in them (which the authors struggle to explain), makes this entire experiment very suspect. (Just look at the reported results for patient 4, which make no sense at all!)
    • C1sc0cat 6y ago
      No offence you might want to brush up on your Maths and how log scales work.
      • infecto 6y ago
        No offense but you should do a better job at explaining whats wrong instead of telling someone to brush up on math.
  • mixmastamyk 6y ago
    Lower numbers may not have enough of an effect on transmission rates.
• Stranger43 6y ago
  The problem is that 99%+ of viruses are either harmless or symbiotic so any method that cant tell harmful from harmless might not give valid results.
  • craigsmansion 6y ago
    > 99%+ of viruses are either harmless or symbiotic There is no such thing as a symbiotic virus.
    • wiml 6y ago
      Placental mammals need certain endogenous retroviruses in order to reproduce.