5 ms·

What I think really matters for most people is not to find out whether they have covid or not, but whether they are infectious or not. I'd really like to see re

by rlpb 3y ago

What I think really matters for most people is not to find out whether they have covid or not, but whether they are infectious or not. I'd really like to see research (any at all!) into how effective different test methods are at predicting infectiousness and am disappointed that this never seems to get addressed. Because who cares if you're asymptomatic but your viral load is low and you're unlikely to infect others? If lack of viral load is the reason that the test is a false negative but that's also correlated with low likelihood that you can infect others, then this understanding is not useful. The test still did it's job for what people needed it for. The full article does not seem to be publicly accessible, so I'm not sure if my comment is already covered.

gwittel 3y ago
I was looking at [1] recently to understand omicron variant positivity length and they cite a few other papers. The article [1] is publicly available. I haven’t checked if all of the others are. * Routsias JG , Mavrouli M , Tsoplou P , Dioikitopoulou K , Tsakris A . Diagnostic performance of rapid antigen tests (RATs) for SARS-CoV-2 and their efficacy in monitoring the infectiousness of COVID-19 patients. Sci Rep. 2021;11(1):22863. doi:10.1038/s41598-021-02197-z * Currie DW , Shah MM , Salvatore PP , et al; CDC COVID-19 Response Epidemiology Field Studies Team. Relationship of SARS-CoV-2 antigen and reverse transcription PCR positivity for viral cultures. Emerg Infect Dis. 2022;28(3):717-720. doi:10.3201/eid2803.211747 * Korenkov M , Poopalasingam N , Madler M , et al. Evaluation of a rapid antigen test to detect SARS-CoV-2 infection and identify potentially infectious individuals. J Clin Microbiol. 2021;59(9):e0089621. doi:10.1128/JCM.00896-21 * Killingley B , Mann A , Kalinova M , et al. Safety, tolerability and viral kinetics during SARS-CoV-2 human challenge in young adults. Nat Med. 2022;28:1031-1041. doi:10.1038/s41591-022-01780-9 [1] COVID-19 Symptoms and Duration of Rapid Antigen Test Positivity at a Community Testing and Surveillance Site During Pre-Delta, Delta, and Omicron BA.1 Periods. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2797070 https://jamanetwork.com/journals/jamanetworkopen/fullarticle...
mathgeek 3y ago
> What I think really matters for most people is not to find out whether they have covid or not, but whether they are infectious or not. While some folks are certainly still worried about spreading the virus, for most folks it's always been about whether a positive test requires them to restrict their movement or activities (e.g. whether or not one could fly on a plane in 2020-2022).
- rlpb 3y ago
  > for most folks it's always been about whether a positive test requires them to restrict their movement or activities Sure but that problem is once removed from the real problem. The underlying reason for restrictions is infectiousness. If tests measured infectiousness accurately, rules on restrictions would follow and use those tests instead.
- Aachen 3y ago
  I think if you go back to polls and news from the time, "most folks" only caring about legal requirements is probably a projection of your opinion and direct contacts'. Pretty sure most people were actually concerned with not infecting others, within reason (which is a different level for everyone, but still)
  - mathgeek 3y ago
    It sounds like you might be conflating two different issues here (being why people were taking covid tests without any symptoms, and why people were doing the superset of actions that would mitigate spreading the virus). There certainly was some overlap where folks who needed to take them for their jobs also wanted to keep people safe, but in general do you believe there were a large number of folks who were or are taking covid tests while not showing symptoms and not being required to take the tests? Additionally, you made a huge leap in assumptions about me that simply aren't true when you assumed what my opinion is/was and how that would project. Let's keep it away from getting personal like that?
- dev_tty01 3y ago
  That may be true for most, but there are many of us who interact with at-risk people (elderly parents, an immune suppressed family member, etc.) and the daily concern is whether or not I might be infectious and potentially bring harm to someone else. I don't care if I have Covid if I can't spread it to someone else. Public service request: There are millions of Americans with compromised immune systems who are finding the current environment treacherous since most people have completely moved on. If we have an interaction with someone who is masked, it would be great if we could just mask up at least during that interaction as a courtesy. That person could be at significant risk and it does no harm to us to mask up for a few minutes to help reduce their risk even if we aren't concerned for ourselves.
mike_hearn 3y ago
It was researched and the results were beyond poor, which is why you never heard about them. IIRC ~75% of PCR positive samples couldn't have any virus cultured from them at all. Viral culturing isn't easy, but PCR tests can trigger on destroyed virus, so it's not a surprise that you can't get replicating virus out of many such samples especially at CT>40. But even if you can grow virus, that doesn't mean someone is infectious. To determine that the ground truth is contact tracing and followup. But this showed that many people who were clearly sick with COVID never infected people they were in close contact with. Even within the home, most cases did not transmit, I think. I got direct experience of this when my wife got COVID and was sick for a couple of weeks, I was then quarantined by the government at home but never got sick. How this could happen was never officially explained. This reveals one of the core scientific problems with the epidemiological simulations that were driving policy: they assumed infection is a one-way event i.e. 100% pre-existing susceptibility. I infect you, because I'm sick, you never were when we get close together we roll a dice and if it comes up 3-6 then you get infected too. This isn't how it works in reality. People's immune systems differ significantly and some are just stronger than others. To be infected I have to be infected but you have to be susceptible. The COVID models basically ignored this and assumed a homogenous population. When adjusted to reflect a more realistic heterogeneous population herd immunity thresholds went down a lot: https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v1 https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v... This research wasn't merely unnoticed, it was actively suppressed. Journals refused to publish it because, "Given the implications for public health, it is appropriate to hold claims around the herd immunity threshold to a very high evidence bar, as these would be interpreted to justify relaxation of interventions, potentially placing people at risk." https://twitter.com/mgmgomes1/status/1291162358962937857 https://twitter.com/mgmgomes1/status/1291162358962937857
- eightysixfour 3y ago
  > People's immune systems differ significantly and some are just stronger than others. Just a nit but stronger is a weird term to describe any functioning immune system. Some genetic trade-off that makes one immune system better suited to blocking COVID infection might make it worse at something else. > To be infected I have to be infected but you have to be susceptible. The COVID models basically ignored this and assumed a homogenous population. And the data used to drive those models is going to be a result of a real world average across the population, so that is fine for nation level decision making. Let’s say you’re using data from two traced cases, a case with high susceptibility (HS) family members and one with low susceptibility (LS) family members. The HS case was in contact with 4 family members, 3 of which became infected. The LS case was in contact with 4 family members and 1 became infected. Two infections, 50% transmission rate. That is fine for modeling and policy, unless we have some sort of a test to determine if you are HS/LS which could be used to make more granular policies. All of this is moot considering the the different variants we never reached some magical “herd immunity” anyways.
lamontcg 3y ago
> but whether they are infectious or not. We don't have a labor and cost effective test for this, and we require the test to be done in a BSL-3 facility. So what remains is that we need to solve public health problems with tests that produce only correlates of infectiousness. Those correlates will be necessarily imperfect, but they're all that we have to craft policy around. The perfect home test which only detects infectious virus doesn't exist. And I'd just like to see more published studies which actually cultured virus rather than using PCR as a proxy for infectious virus, but even that is hard to get. So many lazy scientific studies out there conflating PCR positive with virus, but there's a lot more researchers who can do PCR than researchers than have access+funding to a BSL-3 lab.
cameldrv 3y ago
It's not just whether you are infectious but whether you will become infectious. Hardly anyone cares about covid anymore, but a year or two ago, people would often take a test before they, for example, stayed over at a relative's house. If you take a test right before you arrive, and you stay for a couple of days, if you just caught covid the day you arrived, you'd like to know that. That's where a more sensitive test is really useful. This is a particular problem with newer variants of covid because they multiply much faster. A very low viral load in the nose when the test is taken can turn into a lot in a matter of hours. Anyhow all of this is fairly academic at this point because no one is taking any tests and everyone is doing big events with lots of people.

by rlpb 3y ago

gwittel 3y ago

I was looking at [1] recently to understand omicron variant positivity length and they cite a few other papers. The article [1] is publicly available. I haven’t checked if all of the others are. * Routsias JG , Mavrouli M , Tsoplou P , Dioikitopoulou K , Tsakris A . Diagnostic performance of rapid antigen tests (RATs) for SARS-CoV-2 and their efficacy in monitoring the infectiousness of COVID-19 patients. Sci Rep. 2021;11(1):22863. doi:10.1038/s41598-021-02197-z * Currie DW , Shah MM , Salvatore PP , et al; CDC COVID-19 Response Epidemiology Field Studies Team. Relationship of SARS-CoV-2 antigen and reverse transcription PCR positivity for viral cultures. Emerg Infect Dis. 2022;28(3):717-720. doi:10.3201/eid2803.211747 * Korenkov M , Poopalasingam N , Madler M , et al. Evaluation of a rapid antigen test to detect SARS-CoV-2 infection and identify potentially infectious individuals. J Clin Microbiol. 2021;59(9):e0089621. doi:10.1128/JCM.00896-21 * Killingley B , Mann A , Kalinova M , et al. Safety, tolerability and viral kinetics during SARS-CoV-2 human challenge in young adults. Nat Med. 2022;28:1031-1041. doi:10.1038/s41591-022-01780-9 [1] COVID-19 Symptoms and Duration of Rapid Antigen Test Positivity at a Community Testing and Surveillance Site During Pre-Delta, Delta, and Omicron BA.1 Periods. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2797070 https://jamanetwork.com/journals/jamanetworkopen/fullarticle...

mathgeek 3y ago

> What I think really matters for most people is not to find out whether they have covid or not, but whether they are infectious or not. While some folks are certainly still worried about spreading the virus, for most folks it's always been about whether a positive test requires them to restrict their movement or activities (e.g. whether or not one could fly on a plane in 2020-2022).

rlpb 3y ago
> for most folks it's always been about whether a positive test requires them to restrict their movement or activities Sure but that problem is once removed from the real problem. The underlying reason for restrictions is infectiousness. If tests measured infectiousness accurately, rules on restrictions would follow and use those tests instead.
Aachen 3y ago
I think if you go back to polls and news from the time, "most folks" only caring about legal requirements is probably a projection of your opinion and direct contacts'. Pretty sure most people were actually concerned with not infecting others, within reason (which is a different level for everyone, but still)
- mathgeek 3y ago
  It sounds like you might be conflating two different issues here (being why people were taking covid tests without any symptoms, and why people were doing the superset of actions that would mitigate spreading the virus). There certainly was some overlap where folks who needed to take them for their jobs also wanted to keep people safe, but in general do you believe there were a large number of folks who were or are taking covid tests while not showing symptoms and not being required to take the tests? Additionally, you made a huge leap in assumptions about me that simply aren't true when you assumed what my opinion is/was and how that would project. Let's keep it away from getting personal like that?
dev_tty01 3y ago
That may be true for most, but there are many of us who interact with at-risk people (elderly parents, an immune suppressed family member, etc.) and the daily concern is whether or not I might be infectious and potentially bring harm to someone else. I don't care if I have Covid if I can't spread it to someone else. Public service request: There are millions of Americans with compromised immune systems who are finding the current environment treacherous since most people have completely moved on. If we have an interaction with someone who is masked, it would be great if we could just mask up at least during that interaction as a courtesy. That person could be at significant risk and it does no harm to us to mask up for a few minutes to help reduce their risk even if we aren't concerned for ourselves.

mike_hearn 3y ago

It was researched and the results were beyond poor, which is why you never heard about them. IIRC ~75% of PCR positive samples couldn't have any virus cultured from them at all. Viral culturing isn't easy, but PCR tests can trigger on destroyed virus, so it's not a surprise that you can't get replicating virus out of many such samples especially at CT>40. But even if you can grow virus, that doesn't mean someone is infectious. To determine that the ground truth is contact tracing and followup. But this showed that many people who were clearly sick with COVID never infected people they were in close contact with. Even within the home, most cases did not transmit, I think. I got direct experience of this when my wife got COVID and was sick for a couple of weeks, I was then quarantined by the government at home but never got sick. How this could happen was never officially explained. This reveals one of the core scientific problems with the epidemiological simulations that were driving policy: they assumed infection is a one-way event i.e. 100% pre-existing susceptibility. I infect you, because I'm sick, you never were when we get close together we roll a dice and if it comes up 3-6 then you get infected too. This isn't how it works in reality. People's immune systems differ significantly and some are just stronger than others. To be infected I have to be infected but you have to be susceptible. The COVID models basically ignored this and assumed a homogenous population. When adjusted to reflect a more realistic heterogeneous population herd immunity thresholds went down a lot: https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v1 https://www.medrxiv.org/content/10.1101/2020.04.27.20081893v... This research wasn't merely unnoticed, it was actively suppressed. Journals refused to publish it because, "Given the implications for public health, it is appropriate to hold claims around the herd immunity threshold to a very high evidence bar, as these would be interpreted to justify relaxation of interventions, potentially placing people at risk." https://twitter.com/mgmgomes1/status/1291162358962937857 https://twitter.com/mgmgomes1/status/1291162358962937857

eightysixfour 3y ago
> People's immune systems differ significantly and some are just stronger than others. Just a nit but stronger is a weird term to describe any functioning immune system. Some genetic trade-off that makes one immune system better suited to blocking COVID infection might make it worse at something else. > To be infected I have to be infected but you have to be susceptible. The COVID models basically ignored this and assumed a homogenous population. And the data used to drive those models is going to be a result of a real world average across the population, so that is fine for nation level decision making. Let’s say you’re using data from two traced cases, a case with high susceptibility (HS) family members and one with low susceptibility (LS) family members. The HS case was in contact with 4 family members, 3 of which became infected. The LS case was in contact with 4 family members and 1 became infected. Two infections, 50% transmission rate. That is fine for modeling and policy, unless we have some sort of a test to determine if you are HS/LS which could be used to make more granular policies. All of this is moot considering the the different variants we never reached some magical “herd immunity” anyways.

lamontcg 3y ago

> but whether they are infectious or not. We don't have a labor and cost effective test for this, and we require the test to be done in a BSL-3 facility. So what remains is that we need to solve public health problems with tests that produce only correlates of infectiousness. Those correlates will be necessarily imperfect, but they're all that we have to craft policy around. The perfect home test which only detects infectious virus doesn't exist. And I'd just like to see more published studies which actually cultured virus rather than using PCR as a proxy for infectious virus, but even that is hard to get. So many lazy scientific studies out there conflating PCR positive with virus, but there's a lot more researchers who can do PCR than researchers than have access+funding to a BSL-3 lab.

cameldrv 3y ago

It's not just whether you are infectious but whether you will become infectious. Hardly anyone cares about covid anymore, but a year or two ago, people would often take a test before they, for example, stayed over at a relative's house. If you take a test right before you arrive, and you stay for a couple of days, if you just caught covid the day you arrived, you'd like to know that. That's where a more sensitive test is really useful. This is a particular problem with newer variants of covid because they multiply much faster. A very low viral load in the nose when the test is taken can turn into a lot in a matter of hours. Anyhow all of this is fairly academic at this point because no one is taking any tests and everyone is doing big events with lots of people.