13 ms·

> And wherever we look, infections level off before 10%-20% of the population is infected. This is somewhat mysterious. This is not really true. Bergamo had a

> And wherever we look, infections level off before 10%-20% of the population is infected. This is somewhat mysterious. This is not really true. Bergamo had a 58% infection rate as of last month: https://bergamo.corriere.it/notizie/cronaca/20_maggio_22/bergamo-test-sierologici-cittadini-583percento-positivo-un-giorno-51-contagi-piu-8f6ac032-9c44-11ea-aab2-c1d41bfb67c5.shtml https://bergamo.corriere.it/notizie/cronaca/20_maggio_22/ber... Several prisons have seen infection rates in the 70-80% range: https://www.npr.org/sections/coronavirus-live-updates/2020/04/20/838943211/73-of-inmates-at-an-ohio-prison-test-positive-for-coronavirus https://www.npr.org/sections/coronavirus-live-updates/2020/0... The USS Theodore Roosevelt had an infection rate of 60%: https://www.cdc.gov/mmwr/volumes/69/wr/mm6923e4.htm?s_cid=mm6923e4_e&deliveryName=USCDC_921-DM30202 https://www.cdc.gov/mmwr/volumes/69/wr/mm6923e4.htm?s_cid=mm... A better explanation for the leveling off is simply that social distancing and lockdowns have reduced the spread of the virus.

MiguelVieira 6y ago
Also this Washington choir where over 80% of the attendants were infected https://www.livescience.com/covid-19-superspreader-singing.html https://www.livescience.com/covid-19-superspreader-singing.h... This article is just wishful thinking.
- mlyle 6y ago
  "This phenomenon is called overdispersion, and it means that while on average a patient infects 2 or 3 new people, this average consists of many people infecting nobody, and then some mass spreading events infecting many more."
  - acqq 6y ago
    > then some mass spreading events infecting many more The point is however that it is impossible that the choir selected their members based on the criteria of "members can be only these who will be easily infected with the at the moment still unknown disease." There the existence of the superspreading event to "80% of some random selection" disproves the hypothesis that "on average much less than 80% of the population can be infected at once". That's obviously not true.
    - rightbyte 6y ago
      No. If it is true that say 50% have a harder time catching covid then given that there is a superspreading event at a choir to 80% you need to take into account the others choirs at the other end of the tail. I.e. given 100 choirs there will be a distribution of "not easiely infected" individuals with choirs with few off them. I am not saying anything of the validty of the claim, just that the choir doesnt disprove it.
      - acqq 6y ago
        > I.e. given 100 choirs there will be a distribution of "not easily infected" individuals with choirs with few off them. That's a valid point -- one choir alone would not be enough to be the proof, it could still be an accident that such individuals happened to be in one particular choir, but it's not the only such "random sample." Given that we have more "random samples" of different sizes, they can be observed as contributing to the evidence, the logic of the proof is there, and the evidence accumulates, especially as it can be observed that no specific "traits" of the infected could be recognized to bring "the difference" between "less" and "more" easy infections. One of the arguments supporting the significance in the choir is -- the earlier in the spread of infection we observe such choirs, there's less chance that "100 choirs" from your example were even exposed to the virus, and less chance that that specific choir was exceptional. Similar spreads early in epidemics would also point in non-exceptionality of that one.
    - stupidcar 6y ago
      Just because the choir couldn't select its members on the basis of lower immunity, doesn't it mean it didn't select them (or they self-selected on) the basis of some characteristic(s) that happened to correlate with lower immunity, e.g. age, biological gender, ethnicity, socioeconomic status, etc. The same is true of any other sub-population this is not a true random sample of the global population, like prisons, care homes, even settlements like towns and villages. If you can make any prediction about their members with greater confidence than you could with a random member of the whole population, then they are not random in the sense that matters. Explaining how and why the characteristics of those sub-populations could correlate with greater natural immunity is certainly a challenge to those advocating for the idea of some level of latent immunity. But, likewise, substantially different outcomes in sub-populations that engaged in similar interventions is a challenge for those advocating that only interventions matter. For example, I've not heard a convincing explanation for Germany's relative success based only on the quality of its healthcare system and interventions. That isn't to deny that they played an important role, just that they may not have been the whole story.
ziga 6y ago
Imperial College report showing mobility trends explain over 80% of observed variations in transmission: https://www.imperial.ac.uk/media/imperial-college/medicine/mrc-gida/2020-06-08-COVID19-Report-26.pdf https://www.imperial.ac.uk/media/imperial-college/medicine/m...
- redis_mlc 6y ago
  > Imperial College report Imperial College is always wrong.
  - jpxw 6y ago
    On what?
taeric 6y ago
I think that was sloppy writing at the article. I think what they meant was that the curve leveled off, not total infections. Fits with the next section narrative on assumptions on an easily infected population. Such that, if you maintain close contact, you would still see it spread through more. Explaining the closed populations. But the burst up the curve is driven by the easily infected population more than just mere exposure.
somewhereoutth 6y ago
Curiously enough, after running some simulations in a supposed realistically connected population model (but much smaller n), I found linear growth occurring soon after the exponential phase. I suspect this might be a topological condition (i.e. the due to the distribution of connections) that limits the growth, in the same way a rope will burn linearly if you set fire to one end of it. Of course, a society is more connected than a rope (in the sense we usually have more contacts that just 'up the rope' and 'down the rope'), but continuing exponential growth requires 'fresh' connections at each generation (so no cycles in the graph) - maybe this limits the acceleration of the epidemic.
- leptoniscool 6y ago
  Are you able to share the code for this model?
- yig 6y ago
  There are only so many people, so the growth rate can't stay exponential forever. Eventually it must look like an S-curve.
  - geomark 6y ago
    Right. An S-curve starts out looking exponential. Then begins looking rather linear in the vicinity of the inflection point. And later bends over. If you are in the midst of it then it might be hard to predict the shape of the curve.
dmitriy_ko 6y ago
Every single worker has COVID at one farm https://www.bloomberg.com./news/articles/2020-05-29/every-single-worker-has-covid-at-one-u-s-farm-on-eve-of-harvest https://www.bloomberg.com./news/articles/2020-05-29/every-si...
- FuckButtons 6y ago
  I think this tells you more about their working and sleeping conditions than it does about how the pandemic will play out on a national scale.
  - not2b 6y ago
    But the article claims it will discuss "How around 50% of us appear to have (some?) Cell Mediated Immunity against COVID-19". If we're seeing farms where every single person falls ill, that suggests that 50% of us aren't immune, though I suppose "(some?)" is a cop out.
    - guscost 6y ago
      So those people in one town did not have enough cell-mediated immunity to clear the viral dose from spending all day in an enclosed space with dozens of coworkers shedding the virus. This does not in any way suggest that 50% of the general population cannot have enough cell-mediated immunity (or even immunity from a cross-reactive adaptive/antibody response to another coronavirus) to clear e.g. the viral dose from eating at a restaurant.
      - raducu 6y ago
        Surely it could be true that all population is immune to exposure to exactly half a virion well cooked with sauce, but such an information is pretty useless in any practical way, isn't it? Half immunity in only certain circumstances is useless for all practical purposes.
        salmon30salmon 6y ago
thewarrior 6y ago
I think you’re being too negative here. I’m not an expert. My understanding is given that there is a pre existing T cell response that doesn’t mean that you will not be infected or that you will not have antibodies if infected. However it could totally be possible that when infected you are much less likely to show symptoms,die or spread it to others. It’s a tough hypothesis to completely verify but the dip in deaths and infections in many places in spite of lifting lockdowns lends some support to this theory. This controversial thesis has support from some experts like Dr Sunetra Gupta who teaches epidemiology at Oxford.
- nodamage 6y ago
  I'm not sure what exactly you think is negative? The claim that infections top out at 10-20% is clearly not true. Even if it were true, we don't really know enough yet to conclude that T-cells would be the reason why. > It’s a tough hypothesis to completely verify but the dip in deaths and infections in many places in spite of lifting lockdowns lends some support to this theory. This sounds like a pretty weak correlation to be honest. Just because a lockdown is officially lifted doesn't mean everyone suddenly reverts to their old behaviors.
  - mlyle 6y ago
    > This sounds like a pretty weak correlation to be honest. Just because a lockdown is officially lifted doesn't mean everyone suddenly reverts to their old behaviors. The behavior changes vs. policy changes is interesting. Estimates of Rt were falling before the lockdowns and continued falling at about the same rate without any apparent discontinuity through the intervention. It makes one wonder how effective the policy measures really were-- if they were effective vs. what the population did voluntarily vs. any inherent effects from the structure of the contact network, you'd expect to be able to see some effect in a time series.
  - salmon30salmon 6y ago
    It isn't true _everywhere_. It might be true in some places. For example, towns with young residents and lots of children. Or suburbia where there isn't much incidental contact with others for long periods of time. The goal here, in my opinion, is to _never_ return to the sort of broad stroke lockdown where society stops completely. That is an entirely untenable solution, and any new evidence we have to mitigate the virus without that sort of action is welcome news. We should be cheering these researches on, not vilifying them. They are doing science. It is an imperfect art, it is a series of terrible mistakes that eventually lead to a revelatory moment.
lsllc 6y ago
In Massachusetts (where we have been hit pretty hard by C19) we're trending downwards in a significant way and have been for a few weeks now. But I see more human activity out and about than ever (at least compared to March/April and mask wearing / social distancing is has been pretty obviously in decline for a number weeks now). The state is now well into it's re-opening phase 2 and even with the recent protests, there were only a handful of new infections. Could this not be some version of "herd immunity"? So in cramped conditions such as a warship, cruise liner or prison the virus just spreads so damn quickly (given the 5-14 day incubation) that we see most people getting infected really barely before the incubation is over for the index patient). However in "normal" societal conditions (i.e. where people go to their jobs and are back to their homes at night and are only exposed "occasionally", e.g. on the commuter rail or maybe in a store) that the virus spreads much more slowly and coupled with asymptomatic carriers who (controversially may not "shed" the virus as much, or at all) that reduces the overall input to R0 such that it spreads more slowly and "fizzles out" with R0 < 1. Presumably "herd immunity" isn't a binary thing ... we don't just go from 59% with raging infections at R0 = ~5-6, then suddenly at 60% infected R0 drops to <1? (or whatever numbers you believe "herd immunity" happens at). Maybe the R0 curve just flattens more quickly than we thought?
- redis_mlc 6y ago
  > In Massachusetts (where we have been hit pretty hard by C19) we're trending downwards in a significant way and have been for a few weeks now. Same in California - corona is a health care non-issue here, aside from our governor running for President soon, so it's a political issue. So we'll be the last to leave lockdown, and it's looking like Jan. 2022 now. By non-issue, I mean hospitalizations and deaths according to the official data have been at the same low rate for months, basically flat. California never had a ventilator or ICU shortage at all. (Last time I checked, we had 58 total deaths in SF/Santa Clara County with millions of pre-lockdown arrivals from China.)
  - jlmorton 6y ago
    I'm not sure if you're talking about daily deaths, or in total, but California has had 5,286 deaths as of today, not 58. We also had 81 deaths today specifically. In a perfect world, the point of a lockdown is to arrest the spread of a disease entirely. Unfortunately, we're well past that point in the US. Having failed at that, the goal is not just to keep health care utilization below capacity, but also to buy time to mitigate the disease, by stockpiling PPE and health care supplies, implementing robust contact tracing, and establishing policies for individuals and businesses. California has been prudently relaxing restrictions for a month now, and is now in Stage 3 of the reopening plan.
cashsterling 6y ago
It would be more accurate to state "levels off before 10-20% develop antibodies". The author wrote an article that covers other mechanisms by which the human immune system can fight viral infections. The definition of what 'infected' means is a total gray area. The human body is constantly fighting low-level viral infections. PCR positive doesn't mean you are seriously infected or an active 'spreader'... just means they found some viral RNA in your mouth/throat/nasal-passage. Just means you were definitely exposed and are carrying the virus. Many of those cases were completely/almost asymptomatic, right? N. Italy is it's own unique situation... don't have specific comments there... With an enclosed dense population situation like a prison or a naval vessel... it is interesting that the spread would stop short of ~100% infection once it crosses the 25-50% threshold, given what we understand of the overall high transmissibility of this virus.
xorfish 6y ago
I have seen that "infection level off after 10-20%" multiple times. It is simply not true. Some areas level off at 1-2%, some at 5%, 10, 20% or whatever else. It all depends on when strong social distancing measures were taken. There were only a few places such as NYC or Bergamo, where measures were taken too late and infections went over 20%.
- raducu 6y ago
  I know hn doesn't like sarcasm, but saying that infection level off after 10-20% "naturally" after the world experienced the biggest lockdown since the spanish flu, is like saying the fire I saw on the news was extinguished because I took a pee at the same time. Nevermind resurgences post lockdown in shithole places where people don't follow distancing and don't wear masks -- like India or my belloved Romania -- surely, this fact cannot be explained by this bullshit theory.
  - DyslexicAtheist 6y ago
    > the biggest lockdown since the spanish flu what lockdown has there been in place during the Spanish flu? afaik[1] it was a big cover up in most of the world: > "the reason why it was even called Spanish flu was because Spain was not involved in the war, having remained neutral, and had not imposed wartime censorship." --> hence I assumed Spain was not affected by the propaganda/cover-up efforts and reason for it's spread was precisely the lack of social distancing and lockdowns throughout the world as war ravaged on. [1] https://en.wikipedia.org/wiki/Spanish_flu#Etymology https://en.wikipedia.org/wiki/Spanish_flu#Etymology
    - watwut 6y ago
      They could not keep secret whole time. https://www.nationalgeographic.com/history/2020/03/how-cities-flattened-curve-1918-spanish-flu-pandemic-coronavirus/ https://www.nationalgeographic.com/history/2020/03/how-citie... > on October 3, schools, churches, theaters, and public gathering spaces were shut down > In 1918, a San Francisco health officer shot three people when one refused to wear a mandatory face mask. In Arizona, police handed out $10 fines for those caught without the protective gear.
newmana 6y ago
Sweden has achieved about 15% infection rate and has showed no signs of slowing. https://www.smh.com.au/world/asia/new-beijing-outbreak-raises-fears-for-the-rest-of-the-world-20200618-p553pg.html https://www.smh.com.au/world/asia/new-beijing-outbreak-raise... https://www.worldometers.info/coronavirus/country/sweden/ https://www.worldometers.info/coronavirus/country/sweden/
- GreenHeuristics 6y ago
  No, the 14% figure is for people that self-requested testing. You can see it as an upper boundary, but it won't be the actual figure, which is likely around 8% or so.
  - hcknwscommenter 6y ago
    Exactly. In other words 86% of Swedes who had reason to suspect an infection and wherewithal to request testing and provide sample did not have COVID.
chimprich 6y ago
> A better explanation for the leveling off is simply that social distancing and lockdowns have reduced the spread of the virus. You are probably correct, but it still seems to be the case that the virus spread is slowing faster than expected even with relaxations of lockdown measures. I suspect the explanation is complex. It is probably a combination of factors: individual awareness in reducing social contact, northern hemisphere summer, and individual variability. It's probably not the case that a large proportion of people are immune, but there might be big differences in susceptibility. The examples you mention are either from early in the pandemic where social distancing rules were less habituated, or enclosed environments where transmission is harder to avoid. I'm just guessing, but this would support the European strategy of initial lockdown followed by moderate social controls if outbreaks become more controllable after the initial surge.
- tomp 6y ago
  Why do you think "northern hemisphere summer" would have any (positive) impact? I mean, just look at Brazil, an "eternal summer" country, they're not doing that well... Except if it's the combination of heat+low humidity, there might be counterexamples to that as well though (Iran?).
  - tpm 6y ago
    People spend much more time outside and the school is off. Also the European summer is mostly not as hot as the Brazilian.
  - chimprich 6y ago
    It's a guess, but a plausible one. We know the virus is destroyed quickly by UV light, which is stronger in summer. People spend more time outside in summer, and we know transmission is reduced outside. Other respiratory viruses spread poorly in summer. It's hard to compare with Brazil, because the stats coming out of there are poor and they're making less attempt at controlling the virus compared to almost any other country.
  - dalore 6y ago
    It's not the heat but the UV exposure and people's ability to create vitamin D from it. People in countries that have "eternal summer" tend not to go out in the sun as it's hot. Also skin pigmentation is a big factor.
hcknwscommenter 6y ago
I'm not sure if your sources really say what you imply that they do. Bergamo had a 58% COVID exposure rate as of last month, as determined by serology studies. How many of those had a full blown infection? I suppose detectable antibodies suggests there was at least some level of infection, but a very mild infection plus rapid clearance in a plurality of the population fits with the sentence you quote. The other cites you provide basically show the same thing. Of course social distancing/lockdowns also help. Why not both? The reality is that there are two mysteries here: i) a lot of people are relatively unaffected by the virus and serology shows they were exposed; ii) a lot of people, even under very crowded conditions (USS Teddy R; prisons) just don't get COVID at all. 40% of those on the carrier simply never got it. How is that possible? The prison data is high if we take your the 80% upper level of your range, but you will expect to see those sorts of outliers in small datasets. This is particularly true where the early antibody tests were not very specific (i.e., relatively high false positive rate).
- nodamage 6y ago
  It was not my intent to imply anything about the severity of COVID infections, only that a 10-20% infection threshold is contradicted by several real world examples. While it is still possible that T-cells may have some immunological benefit against COVID, I don't think the 10-20% number qualifies as evidence of that.

MiguelVieira 6y ago

Also this Washington choir where over 80% of the attendants were infected https://www.livescience.com/covid-19-superspreader-singing.html https://www.livescience.com/covid-19-superspreader-singing.h... This article is just wishful thinking.

mlyle 6y ago
"This phenomenon is called overdispersion, and it means that while on average a patient infects 2 or 3 new people, this average consists of many people infecting nobody, and then some mass spreading events infecting many more."
- acqq 6y ago
  > then some mass spreading events infecting many more The point is however that it is impossible that the choir selected their members based on the criteria of "members can be only these who will be easily infected with the at the moment still unknown disease." There the existence of the superspreading event to "80% of some random selection" disproves the hypothesis that "on average much less than 80% of the population can be infected at once". That's obviously not true.
  - rightbyte 6y ago
    No. If it is true that say 50% have a harder time catching covid then given that there is a superspreading event at a choir to 80% you need to take into account the others choirs at the other end of the tail. I.e. given 100 choirs there will be a distribution of "not easiely infected" individuals with choirs with few off them. I am not saying anything of the validty of the claim, just that the choir doesnt disprove it.
    - acqq 6y ago
      > I.e. given 100 choirs there will be a distribution of "not easily infected" individuals with choirs with few off them. That's a valid point -- one choir alone would not be enough to be the proof, it could still be an accident that such individuals happened to be in one particular choir, but it's not the only such "random sample." Given that we have more "random samples" of different sizes, they can be observed as contributing to the evidence, the logic of the proof is there, and the evidence accumulates, especially as it can be observed that no specific "traits" of the infected could be recognized to bring "the difference" between "less" and "more" easy infections. One of the arguments supporting the significance in the choir is -- the earlier in the spread of infection we observe such choirs, there's less chance that "100 choirs" from your example were even exposed to the virus, and less chance that that specific choir was exceptional. Similar spreads early in epidemics would also point in non-exceptionality of that one.
  - stupidcar 6y ago
    Just because the choir couldn't select its members on the basis of lower immunity, doesn't it mean it didn't select them (or they self-selected on) the basis of some characteristic(s) that happened to correlate with lower immunity, e.g. age, biological gender, ethnicity, socioeconomic status, etc. The same is true of any other sub-population this is not a true random sample of the global population, like prisons, care homes, even settlements like towns and villages. If you can make any prediction about their members with greater confidence than you could with a random member of the whole population, then they are not random in the sense that matters. Explaining how and why the characteristics of those sub-populations could correlate with greater natural immunity is certainly a challenge to those advocating for the idea of some level of latent immunity. But, likewise, substantially different outcomes in sub-populations that engaged in similar interventions is a challenge for those advocating that only interventions matter. For example, I've not heard a convincing explanation for Germany's relative success based only on the quality of its healthcare system and interventions. That isn't to deny that they played an important role, just that they may not have been the whole story.

ziga 6y ago

Imperial College report showing mobility trends explain over 80% of observed variations in transmission: https://www.imperial.ac.uk/media/imperial-college/medicine/mrc-gida/2020-06-08-COVID19-Report-26.pdf https://www.imperial.ac.uk/media/imperial-college/medicine/m...

redis_mlc 6y ago
> Imperial College report Imperial College is always wrong.
- jpxw 6y ago
  On what?

taeric 6y ago

I think that was sloppy writing at the article. I think what they meant was that the curve leveled off, not total infections. Fits with the next section narrative on assumptions on an easily infected population. Such that, if you maintain close contact, you would still see it spread through more. Explaining the closed populations. But the burst up the curve is driven by the easily infected population more than just mere exposure.

somewhereoutth 6y ago

Curiously enough, after running some simulations in a supposed realistically connected population model (but much smaller n), I found linear growth occurring soon after the exponential phase. I suspect this might be a topological condition (i.e. the due to the distribution of connections) that limits the growth, in the same way a rope will burn linearly if you set fire to one end of it. Of course, a society is more connected than a rope (in the sense we usually have more contacts that just 'up the rope' and 'down the rope'), but continuing exponential growth requires 'fresh' connections at each generation (so no cycles in the graph) - maybe this limits the acceleration of the epidemic.

leptoniscool 6y ago
Are you able to share the code for this model?
yig 6y ago
There are only so many people, so the growth rate can't stay exponential forever. Eventually it must look like an S-curve.
- geomark 6y ago
  Right. An S-curve starts out looking exponential. Then begins looking rather linear in the vicinity of the inflection point. And later bends over. If you are in the midst of it then it might be hard to predict the shape of the curve.

dmitriy_ko 6y ago

Every single worker has COVID at one farm https://www.bloomberg.com./news/articles/2020-05-29/every-single-worker-has-covid-at-one-u-s-farm-on-eve-of-harvest https://www.bloomberg.com./news/articles/2020-05-29/every-si...

FuckButtons 6y ago
I think this tells you more about their working and sleeping conditions than it does about how the pandemic will play out on a national scale.
- not2b 6y ago
  But the article claims it will discuss "How around 50% of us appear to have (some?) Cell Mediated Immunity against COVID-19". If we're seeing farms where every single person falls ill, that suggests that 50% of us aren't immune, though I suppose "(some?)" is a cop out.
  - guscost 6y ago
    So those people in one town did not have enough cell-mediated immunity to clear the viral dose from spending all day in an enclosed space with dozens of coworkers shedding the virus. This does not in any way suggest that 50% of the general population cannot have enough cell-mediated immunity (or even immunity from a cross-reactive adaptive/antibody response to another coronavirus) to clear e.g. the viral dose from eating at a restaurant.
    - raducu 6y ago
      Surely it could be true that all population is immune to exposure to exactly half a virion well cooked with sauce, but such an information is pretty useless in any practical way, isn't it? Half immunity in only certain circumstances is useless for all practical purposes.
      - salmon30salmon 6y ago

thewarrior 6y ago

I think you’re being too negative here. I’m not an expert. My understanding is given that there is a pre existing T cell response that doesn’t mean that you will not be infected or that you will not have antibodies if infected. However it could totally be possible that when infected you are much less likely to show symptoms,die or spread it to others. It’s a tough hypothesis to completely verify but the dip in deaths and infections in many places in spite of lifting lockdowns lends some support to this theory. This controversial thesis has support from some experts like Dr Sunetra Gupta who teaches epidemiology at Oxford.

nodamage 6y ago
I'm not sure what exactly you think is negative? The claim that infections top out at 10-20% is clearly not true. Even if it were true, we don't really know enough yet to conclude that T-cells would be the reason why. > It’s a tough hypothesis to completely verify but the dip in deaths and infections in many places in spite of lifting lockdowns lends some support to this theory. This sounds like a pretty weak correlation to be honest. Just because a lockdown is officially lifted doesn't mean everyone suddenly reverts to their old behaviors.
- mlyle 6y ago
  > This sounds like a pretty weak correlation to be honest. Just because a lockdown is officially lifted doesn't mean everyone suddenly reverts to their old behaviors. The behavior changes vs. policy changes is interesting. Estimates of Rt were falling before the lockdowns and continued falling at about the same rate without any apparent discontinuity through the intervention. It makes one wonder how effective the policy measures really were-- if they were effective vs. what the population did voluntarily vs. any inherent effects from the structure of the contact network, you'd expect to be able to see some effect in a time series.
- salmon30salmon 6y ago
  It isn't true _everywhere_. It might be true in some places. For example, towns with young residents and lots of children. Or suburbia where there isn't much incidental contact with others for long periods of time. The goal here, in my opinion, is to _never_ return to the sort of broad stroke lockdown where society stops completely. That is an entirely untenable solution, and any new evidence we have to mitigate the virus without that sort of action is welcome news. We should be cheering these researches on, not vilifying them. They are doing science. It is an imperfect art, it is a series of terrible mistakes that eventually lead to a revelatory moment.

lsllc 6y ago

In Massachusetts (where we have been hit pretty hard by C19) we're trending downwards in a significant way and have been for a few weeks now. But I see more human activity out and about than ever (at least compared to March/April and mask wearing / social distancing is has been pretty obviously in decline for a number weeks now). The state is now well into it's re-opening phase 2 and even with the recent protests, there were only a handful of new infections. Could this not be some version of "herd immunity"? So in cramped conditions such as a warship, cruise liner or prison the virus just spreads so damn quickly (given the 5-14 day incubation) that we see most people getting infected really barely before the incubation is over for the index patient). However in "normal" societal conditions (i.e. where people go to their jobs and are back to their homes at night and are only exposed "occasionally", e.g. on the commuter rail or maybe in a store) that the virus spreads much more slowly and coupled with asymptomatic carriers who (controversially may not "shed" the virus as much, or at all) that reduces the overall input to R0 such that it spreads more slowly and "fizzles out" with R0 < 1. Presumably "herd immunity" isn't a binary thing ... we don't just go from 59% with raging infections at R0 = ~5-6, then suddenly at 60% infected R0 drops to <1? (or whatever numbers you believe "herd immunity" happens at). Maybe the R0 curve just flattens more quickly than we thought?

redis_mlc 6y ago
> In Massachusetts (where we have been hit pretty hard by C19) we're trending downwards in a significant way and have been for a few weeks now. Same in California - corona is a health care non-issue here, aside from our governor running for President soon, so it's a political issue. So we'll be the last to leave lockdown, and it's looking like Jan. 2022 now. By non-issue, I mean hospitalizations and deaths according to the official data have been at the same low rate for months, basically flat. California never had a ventilator or ICU shortage at all. (Last time I checked, we had 58 total deaths in SF/Santa Clara County with millions of pre-lockdown arrivals from China.)
- jlmorton 6y ago
  I'm not sure if you're talking about daily deaths, or in total, but California has had 5,286 deaths as of today, not 58. We also had 81 deaths today specifically. In a perfect world, the point of a lockdown is to arrest the spread of a disease entirely. Unfortunately, we're well past that point in the US. Having failed at that, the goal is not just to keep health care utilization below capacity, but also to buy time to mitigate the disease, by stockpiling PPE and health care supplies, implementing robust contact tracing, and establishing policies for individuals and businesses. California has been prudently relaxing restrictions for a month now, and is now in Stage 3 of the reopening plan.

cashsterling 6y ago

It would be more accurate to state "levels off before 10-20% develop antibodies". The author wrote an article that covers other mechanisms by which the human immune system can fight viral infections. The definition of what 'infected' means is a total gray area. The human body is constantly fighting low-level viral infections. PCR positive doesn't mean you are seriously infected or an active 'spreader'... just means they found some viral RNA in your mouth/throat/nasal-passage. Just means you were definitely exposed and are carrying the virus. Many of those cases were completely/almost asymptomatic, right? N. Italy is it's own unique situation... don't have specific comments there... With an enclosed dense population situation like a prison or a naval vessel... it is interesting that the spread would stop short of ~100% infection once it crosses the 25-50% threshold, given what we understand of the overall high transmissibility of this virus.

xorfish 6y ago

I have seen that "infection level off after 10-20%" multiple times. It is simply not true. Some areas level off at 1-2%, some at 5%, 10, 20% or whatever else. It all depends on when strong social distancing measures were taken. There were only a few places such as NYC or Bergamo, where measures were taken too late and infections went over 20%.

raducu 6y ago
I know hn doesn't like sarcasm, but saying that infection level off after 10-20% "naturally" after the world experienced the biggest lockdown since the spanish flu, is like saying the fire I saw on the news was extinguished because I took a pee at the same time. Nevermind resurgences post lockdown in shithole places where people don't follow distancing and don't wear masks -- like India or my belloved Romania -- surely, this fact cannot be explained by this bullshit theory.
- DyslexicAtheist 6y ago
  > the biggest lockdown since the spanish flu what lockdown has there been in place during the Spanish flu? afaik[1] it was a big cover up in most of the world: > "the reason why it was even called Spanish flu was because Spain was not involved in the war, having remained neutral, and had not imposed wartime censorship." --> hence I assumed Spain was not affected by the propaganda/cover-up efforts and reason for it's spread was precisely the lack of social distancing and lockdowns throughout the world as war ravaged on. [1] https://en.wikipedia.org/wiki/Spanish_flu#Etymology https://en.wikipedia.org/wiki/Spanish_flu#Etymology
  - watwut 6y ago
    They could not keep secret whole time. https://www.nationalgeographic.com/history/2020/03/how-cities-flattened-curve-1918-spanish-flu-pandemic-coronavirus/ https://www.nationalgeographic.com/history/2020/03/how-citie... > on October 3, schools, churches, theaters, and public gathering spaces were shut down > In 1918, a San Francisco health officer shot three people when one refused to wear a mandatory face mask. In Arizona, police handed out $10 fines for those caught without the protective gear.

newmana 6y ago

Sweden has achieved about 15% infection rate and has showed no signs of slowing. https://www.smh.com.au/world/asia/new-beijing-outbreak-raises-fears-for-the-rest-of-the-world-20200618-p553pg.html https://www.smh.com.au/world/asia/new-beijing-outbreak-raise... https://www.worldometers.info/coronavirus/country/sweden/ https://www.worldometers.info/coronavirus/country/sweden/

GreenHeuristics 6y ago
No, the 14% figure is for people that self-requested testing. You can see it as an upper boundary, but it won't be the actual figure, which is likely around 8% or so.
- hcknwscommenter 6y ago
  Exactly. In other words 86% of Swedes who had reason to suspect an infection and wherewithal to request testing and provide sample did not have COVID.

chimprich 6y ago

> A better explanation for the leveling off is simply that social distancing and lockdowns have reduced the spread of the virus. You are probably correct, but it still seems to be the case that the virus spread is slowing faster than expected even with relaxations of lockdown measures. I suspect the explanation is complex. It is probably a combination of factors: individual awareness in reducing social contact, northern hemisphere summer, and individual variability. It's probably not the case that a large proportion of people are immune, but there might be big differences in susceptibility. The examples you mention are either from early in the pandemic where social distancing rules were less habituated, or enclosed environments where transmission is harder to avoid. I'm just guessing, but this would support the European strategy of initial lockdown followed by moderate social controls if outbreaks become more controllable after the initial surge.

tomp 6y ago
Why do you think "northern hemisphere summer" would have any (positive) impact? I mean, just look at Brazil, an "eternal summer" country, they're not doing that well... Except if it's the combination of heat+low humidity, there might be counterexamples to that as well though (Iran?).
- tpm 6y ago
  People spend much more time outside and the school is off. Also the European summer is mostly not as hot as the Brazilian.
- chimprich 6y ago
  It's a guess, but a plausible one. We know the virus is destroyed quickly by UV light, which is stronger in summer. People spend more time outside in summer, and we know transmission is reduced outside. Other respiratory viruses spread poorly in summer. It's hard to compare with Brazil, because the stats coming out of there are poor and they're making less attempt at controlling the virus compared to almost any other country.
- dalore 6y ago
  It's not the heat but the UV exposure and people's ability to create vitamin D from it. People in countries that have "eternal summer" tend not to go out in the sun as it's hot. Also skin pigmentation is a big factor.

hcknwscommenter 6y ago

I'm not sure if your sources really say what you imply that they do. Bergamo had a 58% COVID exposure rate as of last month, as determined by serology studies. How many of those had a full blown infection? I suppose detectable antibodies suggests there was at least some level of infection, but a very mild infection plus rapid clearance in a plurality of the population fits with the sentence you quote. The other cites you provide basically show the same thing. Of course social distancing/lockdowns also help. Why not both? The reality is that there are two mysteries here: i) a lot of people are relatively unaffected by the virus and serology shows they were exposed; ii) a lot of people, even under very crowded conditions (USS Teddy R; prisons) just don't get COVID at all. 40% of those on the carrier simply never got it. How is that possible? The prison data is high if we take your the 80% upper level of your range, but you will expect to see those sorts of outliers in small datasets. This is particularly true where the early antibody tests were not very specific (i.e., relatively high false positive rate).

nodamage 6y ago
It was not my intent to imply anything about the severity of COVID infections, only that a 10-20% infection threshold is contradicted by several real world examples. While it is still possible that T-cells may have some immunological benefit against COVID, I don't think the 10-20% number qualifies as evidence of that.