5 ms·

The engines of SARS-CoV-2 spread

52 points by hanklazard 6y ago

jeffrallen 6y ago
I need a tldr on this, stat. Even timr's response is giving me headaches. I don't consider household infection avoidable. I'm going to keep hugging my kids and wife. So if that's off the table then what?
- sokoloff 6y ago
  If it were Ebola instead, would you keep doing that? That suggests to me that it's a choice/avoidable. Given the overall risk level, I agree with your decision [and do the same], but it does seem avoidable if we wanted to choose that.
  - jeffrallen 6y ago
    Ebola does not have asymptomatic transmission, which is what we risk when we keep living family life.
  - schwartzworld 6y ago
    maybe above a certain age it's avoidable. I'm pretty sure my two year old isn't going to keep her fingers out of my mouth no matter what I explain.
- ReactiveJelly 6y ago
  Yeah, I'm not understanding it. And I don't think useful information should be hard to understand, so I hope someone can clarify. Here's what I figure: - If I caught it a week ago, I would be sick by now - So, I didn't have it a week ago - I haven't had contact with anyone outside my house for a week And it's the same for my spouse. We can't catch it from each other if we don't have it. So, the payoff for distancing and masks inside the house seems very low for a very high cost. I can only stand 6 months and counting of lockdown because my best friend (spouse) is locked down with me. We did have a scare once, and did a 2-week quarantine within the house. I just don't see any point doing that all the time when neither of us have it right now.
  - _jahh 6y ago
    From what I understand this is more of a concern in larger and especially multi generational families. You're absolutely right with only two there is less or no concern.
fortran77 6y ago
They need to ban in-flight use of CPAP now. I was shocked when I had to fly and the person next to me mid-flight, started using a machine that the CDC, the NIH and many others warn will aerosolize SARS-CoV-2 and other viruses and spread them far and wide. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7298691/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7298691/
- gameswithgo 6y ago
  im more shocked that anyone gets on a plane right now at all, than i am worried that occasionally some person on a flight uses a cpap machines
  - fortran77 6y ago
    Sometimes family emergencies leave little choice. I certainly won't fly unless I have to.
  - imjared 6y ago
    I was hesitant to fly early this summer. As months ticked on, I didn't see any news about full flights getting infected in the way I would expect. I've seen countless stories of "x people went to event and 90% got Covid a week later" but as far as I could discern, almost nothing like that had come from flying. I chose to fly with a carrier (Delta) that I felt was handling the situation more responsibly by blocking middle seats. I'll say that the whole experience felt pretty fine. Airlines and airports have taken reasonable precautions at every step of the experience and I'll say I felt substantially more comfortable flying (except for wearing a mask for ~10 hours) than I've felt doing other risky activities like dining outside or going for a run/bike ride on a crowded trail in the park.
    - dhimes 6y ago
      Good to know. I understand they exchanging the air with the outside every couple of minutes now, too, which seems very smart.
timr 6y ago
This is a frustrating editorial. The authors make a credible case that the majority of transmission occurs inside households (where we are doing little/nothing to prevent spread), and that the probability of "community transmission" (where we are doing a lot, at great societal cost) is low...but they word it in a way that hides the impact of what they're saying: "For SARS-CoV-2, studies suggest that ∼10% of cases cause 80% of infections (1). Overdispersion is characterized by a large number of people who infect no one, and most people who do transmit infect a low-to-moderate number of individuals." "overdispersion means that most infected individuals who enter a community will not transmit, so many introductions may occur before an epidemic takes hold; likewise, overdispersion also increases the probability of disease extinction as the epidemic recedes and fewer people are infected." "If transmission is highly overdispersed, broad and untargeted interventions may be less effective than expected, whereas interventions targeted at settings conducive to superspreading (such as mass gatherings and hospitals) may have an outsized effect." They then make the argument that this pattern of transmission makes it unlikely for things like travel bans to have an effect: "Only a small number of such long-distance connections are needed to create a “small world” network in which only a few infection events can transmit the virus between any two individuals worldwide. This is one reason why early travel bans could not stop the global spread of SARS-CoV-2, although they may have slowed the pandemic." Then they move on to the importance of preventing spread in the household, via relatively inexpensive interventions: "Moving from international to household scales, the burdens of interventions are shared by more people; there are few international travelers, but nearly everyone lives in households and communities. Measures to reduce household spread may appear particularly challenging, but because they directly affect so many, they need not be perfect. Household mask use and partitioning of home spaces, isolation or quarantine outside the home, and, in the future, household provision of preventive drugs could have large effects even if they offer only modest protection." So overall, everything in this article draws a (IMHO convincing) conclusion that our interventions should be focused on household transmission. Then they go on to say that community transmission control measures must be draconian in order to be effective: "Conversely, control measures at larger spatial scales (for example, interregional) must be widely implemented and highly effective to contain the virus. Indeed, few nations have managed to curb infection without stay-at-home orders and business closures, particularly after community transmission is prevalent." Unfortunately, they've worded this in a weird way, which makes it sounds like they're advocating for such measures, when they're actually doing the opposite; the article is fundamentally about how even if you miss one transmission event, it's enough to keep the graph connected. So overall, this article is saying that we're doing it wrong: we should be focused on the middle of the bell curve, where modest efforts can yield greater results, instead of spending huge amounts of money to unsuccessfully filter out infrequent, improbable events. Said in a way that might be more intuitive for programmers, it's similar to the expenses required to ensure system uptime. While it's possible to obtain (e.g.) 95% uptime with very little effort, getting to 99% requires significantly greater costs (redundant servers, etc). Getting to 99.9% requires significantly more expense (e.g. datacenter redundancy, hot deploys, etc.), so on and so forth. Every additional fraction of a percent of bad stuff that you try to stop costs orders of magnitude more effort. The same thing applies here: it's relatively inexpensive to ask people to do things at home, but shutting down all businesses and international travel is an incredibly expensive intervention, aimed at the tails of the distribution.

52 points by hanklazard 6y ago

I need a tldr on this, stat. Even timr's response is giving me headaches. I don't consider household infection avoidable. I'm going to keep hugging my kids and wife. So if that's off the table then what?

sokoloff 6y ago
If it were Ebola instead, would you keep doing that? That suggests to me that it's a choice/avoidable. Given the overall risk level, I agree with your decision [and do the same], but it does seem avoidable if we wanted to choose that.
- jeffrallen 6y ago
  Ebola does not have asymptomatic transmission, which is what we risk when we keep living family life.
- schwartzworld 6y ago
  maybe above a certain age it's avoidable. I'm pretty sure my two year old isn't going to keep her fingers out of my mouth no matter what I explain.
ReactiveJelly 6y ago
Yeah, I'm not understanding it. And I don't think useful information should be hard to understand, so I hope someone can clarify. Here's what I figure: - If I caught it a week ago, I would be sick by now - So, I didn't have it a week ago - I haven't had contact with anyone outside my house for a week And it's the same for my spouse. We can't catch it from each other if we don't have it. So, the payoff for distancing and masks inside the house seems very low for a very high cost. I can only stand 6 months and counting of lockdown because my best friend (spouse) is locked down with me. We did have a scare once, and did a 2-week quarantine within the house. I just don't see any point doing that all the time when neither of us have it right now.
- _jahh 6y ago
  From what I understand this is more of a concern in larger and especially multi generational families. You're absolutely right with only two there is less or no concern.

fortran77 6y ago

They need to ban in-flight use of CPAP now. I was shocked when I had to fly and the person next to me mid-flight, started using a machine that the CDC, the NIH and many others warn will aerosolize SARS-CoV-2 and other viruses and spread them far and wide. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7298691/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7298691/

gameswithgo 6y ago
im more shocked that anyone gets on a plane right now at all, than i am worried that occasionally some person on a flight uses a cpap machines
- fortran77 6y ago
  Sometimes family emergencies leave little choice. I certainly won't fly unless I have to.
- imjared 6y ago
  I was hesitant to fly early this summer. As months ticked on, I didn't see any news about full flights getting infected in the way I would expect. I've seen countless stories of "x people went to event and 90% got Covid a week later" but as far as I could discern, almost nothing like that had come from flying. I chose to fly with a carrier (Delta) that I felt was handling the situation more responsibly by blocking middle seats. I'll say that the whole experience felt pretty fine. Airlines and airports have taken reasonable precautions at every step of the experience and I'll say I felt substantially more comfortable flying (except for wearing a mask for ~10 hours) than I've felt doing other risky activities like dining outside or going for a run/bike ride on a crowded trail in the park.
  - dhimes 6y ago
    Good to know. I understand they exchanging the air with the outside every couple of minutes now, too, which seems very smart.

timr 6y ago

This is a frustrating editorial. The authors make a credible case that the majority of transmission occurs inside households (where we are doing little/nothing to prevent spread), and that the probability of "community transmission" (where we are doing a lot, at great societal cost) is low...but they word it in a way that hides the impact of what they're saying: "For SARS-CoV-2, studies suggest that ∼10% of cases cause 80% of infections (1). Overdispersion is characterized by a large number of people who infect no one, and most people who do transmit infect a low-to-moderate number of individuals." "overdispersion means that most infected individuals who enter a community will not transmit, so many introductions may occur before an epidemic takes hold; likewise, overdispersion also increases the probability of disease extinction as the epidemic recedes and fewer people are infected." "If transmission is highly overdispersed, broad and untargeted interventions may be less effective than expected, whereas interventions targeted at settings conducive to superspreading (such as mass gatherings and hospitals) may have an outsized effect." They then make the argument that this pattern of transmission makes it unlikely for things like travel bans to have an effect: "Only a small number of such long-distance connections are needed to create a “small world” network in which only a few infection events can transmit the virus between any two individuals worldwide. This is one reason why early travel bans could not stop the global spread of SARS-CoV-2, although they may have slowed the pandemic." Then they move on to the importance of preventing spread in the household, via relatively inexpensive interventions: "Moving from international to household scales, the burdens of interventions are shared by more people; there are few international travelers, but nearly everyone lives in households and communities. Measures to reduce household spread may appear particularly challenging, but because they directly affect so many, they need not be perfect. Household mask use and partitioning of home spaces, isolation or quarantine outside the home, and, in the future, household provision of preventive drugs could have large effects even if they offer only modest protection." So overall, everything in this article draws a (IMHO convincing) conclusion that our interventions should be focused on household transmission. Then they go on to say that community transmission control measures must be draconian in order to be effective: "Conversely, control measures at larger spatial scales (for example, interregional) must be widely implemented and highly effective to contain the virus. Indeed, few nations have managed to curb infection without stay-at-home orders and business closures, particularly after community transmission is prevalent." Unfortunately, they've worded this in a weird way, which makes it sounds like they're advocating for such measures, when they're actually doing the opposite; the article is fundamentally about how even if you miss one transmission event, it's enough to keep the graph connected. So overall, this article is saying that we're doing it wrong: we should be focused on the middle of the bell curve, where modest efforts can yield greater results, instead of spending huge amounts of money to unsuccessfully filter out infrequent, improbable events. Said in a way that might be more intuitive for programmers, it's similar to the expenses required to ensure system uptime. While it's possible to obtain (e.g.) 95% uptime with very little effort, getting to 99% requires significantly greater costs (redundant servers, etc). Getting to 99.9% requires significantly more expense (e.g. datacenter redundancy, hot deploys, etc.), so on and so forth. Every additional fraction of a percent of bad stuff that you try to stop costs orders of magnitude more effort. The same thing applies here: it's relatively inexpensive to ask people to do things at home, but shutting down all businesses and international travel is an incredibly expensive intervention, aimed at the tails of the distribution.