I think the theory is "there are few enough we didn't notice."
There's other weird effects going on -- some countries that look really really similar have vastly different experiences with the virus. (Canonical example is DR and Haiti, although the situation is dynamic enough no-one knows if that'll last.)
My takeaway from the difficulty in measuring this thing is that there is pretty high variance in transmission. Some carriers spread it REALLY well. Some carriers spread it poorly. With a lot of variance it matters a ton to figure out what is the deal with high-transmission situations. My take so far is we have some clues but no certainty. (Seems to spread in public transit and healthcare environments more rapidly, but slower than you'd expect in schools and prisons.)
It'd clearly be a gigantic win in terms of intervention policy to understand this better, and we simply cannot do that without extensive contact tracing so we know what's going on. They're doing a pretty good job of this in China, HK, Taiwan, South Korea. As nearly as I can tell we're doing a dismally poor job in the US and Europe.
You read papers that have diagrams of restaurant tables and bus seating charts from China. In the US it's hard to get stats on aggregate nursing home vs non-nursing home fatality rates. Maybe it takes some time for these papers to come out, but I don't see evidence that high-quality pre-pub contact tracing data is being relied on to develop policy responses.
That is a huge oversimplification.
According the Chinese study there is no asymptomatic transmission. So most of the numbers do not even make sense.
Transmission within a masked & lockdown population is still large. Does not even seem to change... Because there is no asymptomatic transmission. We need quarantine instead of sick people.
Masks have health side-effects, because 99% of people do not follow the OSHO safety standards.
The transmission within a household between partners has an average of 27%. Another extremely weird number.
Did the tests give false positives? Is the disease misidentified?
Or did the others already have T-cell herd-immunity?
So the real question is: What is causing transmission?
And note the R does not show that at all, and focusing on that gives us the wrong solutions.
There may be other factors that create a high transmission. Some doctors listed an extreme long survival time of the virus (up to 16 days under good conditions). So maybe it transmits mainly via surfaces and not via the air.
That might explain why it can spread within a population under a military lockdown.
But that latter might also be explained with the false positives from a PCR test (or similar test). Or the natural immunity of most people creating partial herd-immunity within the population.
yes, that's pretty much exactly what i'm saying: all the data we have is that it spreads exactly as you say, sitting with somebody for an extended period of time. because that's the sort of thing that people remember, and tell the contact tracers about.
but at least in my region, the majority of cases still don't have a known source. maybe that's because people are catching it in scenarios where they're in close proximity to somebody for extended periods of time but forget about it when the contact tracers call them, and all cases are spread that way.
or maybe it's spreading in grocery stores and other casual contact scenarios but that's just impossible to measure or count. we keep hearing that there's no evidence of it spreading in schools, and yet as long as students are in school it spreads a lot more among students. is it not spreading there, or is it just really difficult to find the evidence of that?
What's interesting is that none of the answers seem definitive.
1) 'Mask wearing' - we know even cloth masks will help reduce spread, but not by what factor overall. We don't know the real vectors here.
2) Someone mentioned 'hygiene' - do the Japanese really wash their hands every time they enter the house? Or do they 'rinse their food' i.e. maybe package handling is a big vector.
3) 'Early border closing' - it only takes a handful of cases to cause the spread. Nobody has been able to 'keep it out' this way.
4) Some cynical commenters indicated it's due to low testing and governments wanton to 'keep the numbers down' which is hard to buy because the truth would hit hard when hospitals start to fill up.
5) Timing. Taking strong measures early may have made all the difference. If you can truly keep the numbers small, it becomes more manageable on a case by case basis.
Or all of the above.
I hope we are able to isolate the real transmission vectors that affect R0, but we may never really know.
Part of me wonders: if this happened from one event, just how terrible must the odds be that the virus isn't spreading similarly under our noses from contacts that haven't been identified?
Transmission via asymptotic carriers isn't a new thing. It's been known for months (e.g. the analysis of the first cluster in Germany) and is one of the main reasons this virus is so problematic.
Those numbers really don't tell you anything about how viable surface transmission is as a vector from person to person. It doesn't seem to be a major transmission pathway based on all the available evidence so far.
No that is not obvious at all. It doesn't depend on the transmission rate, just on how many people get infected. Higher transmission rate just means it spreads faster, not that it infects more people in the end.
These are probably good/important points in a totally different context, but in this discussion, talking about how the virus has been transmitted, and the effect of infected individuals to quarantine or not, it feels a little strange. problematic moral impulses notwithstanding, the virus does indeed transmit person to person
> their leaders said that “asymptotic transmission is rare” which is a deadly lie
How it is a lie? People talk a lot about the presence of asymptomatic transmission, but:
1. No one knows for sure if completely asymptomatic people are contagious, and the extent of such contagiousness;
2. People equate asymptomatic with presymptomatic, which is a totally different story;
3. The evidence is at best, inconsistent. There is one case report of a non-contagious "asymptomatic" (reading the paper, the symptoms were there, just not the usual ones), and Singapore contact tracing of a number of completely asymptomatic people did not seem to find infected people in contact with them.
Presymptomatic state is a different matter, and it looks more contagious, but again, a lot of it is speculation, because it's really hard to measure.
This transmission is there. The extent of it is not known.
Can you put together some actual data then? Like, get all the relevant data for hospitalizations and deaths by locality and find a correlation against climate data? And then do the same for things like density, how early and strictly social distancing measures were put into effect, etc., and see if it has more or less correlation than those?
My gut feeling here is that climate is not a significant factor, but that those others are. And you haven't come close to actually demonstrating it with rigor beyond it just being a guess that you have (which is fine; guesses are useful).
And you're right, the connection between climate and the spread of a disease is well known, which is why if it were relevant here there would be lots of people besides you talking about it. The articles you linked do seem to show that the virus might not survive for quite as long on surfaces at high temperatures and humidities, but that's just not really that relevant for how this disease spreads. People are primarily either inhaling droplets directly, or touching things that others have touched recently and then getting it into their face. The virus surviving for hours on a surface before being touched and then touched again to a face orifice was always on the long tail of transmission methods, so flattening that tail a little bit doesn't make a meaningful difference in the overall spread of the virus.
According to this article, it seems like a lot of health care workers are catching the disease. Even the westerners who are familiar with the transmission mechanism of the disease. Therefore, isn't possible that we are underestimating how easily the disease can spread?
The first study also touches on the point of transmission through surfaces which they argue should be at the very most 10% of all cases but probably less and a German virologist who's one of the leading experts in coronaviruses, Prof. Dr. Drosten, said that he and many others believe that surface transmission is almost negligible: https://www.ndr.de/nachrichten/info/coronaskript162.pdf (in German).
There is no such thing as a trace/undetectable transmission. These studies have been going on a long time now with large numbers of participants, replicated in multiple countries/different populations. The results are very strong and not based on measuring viral levels.
Is it? I read the original comment as saying there were significantly different symptoms based on the transmission method. Even assuming that the transmission method results in a significantly different viral load, that's not enough to explain differing symptoms since there's not a whole lot of observable difference between cases with different severities[1,2]. There are some studies that show a relationship, but nothing strong enough to explain a dramatic difference.
If it's true that the transmission method makes a big difference, it's more likely due to some other reason. E.g. maybe mild strains spread more easily in the air (although as far as I know there's no evidence that's true.)
Could it have to do with population density (perhaps even only in certain areas)? My reasoning is that you could have high transmission among the minority that doesn't wear masks, and that might suffice to make the absolute case-load quite high.
Because there are multiple paths and the virus really spreads like a wave frontier in a 10 dimensional space of human to human contacts graph. The virus also spreads in a non uniform way: it's not about the distance between two interacted persons, but about the nature of their interaction, whether they weared masks and so on. The virus also really likes to stick to surfaces, like door handles or plastic wraps, and this vector of transmission is very difficult to trace even manually. Think of credit cards. The virus floats in the air like smoke if someone coughed and others may catch it this way. An app can't account for that and instead builds a social graph of interactions. The app would notice a lot of people crowded in a parking lot and would assume the virus was transmitted between those 50 people, but it wouldn't know that all those people sit in their cars, so the app just made the transmission chain 50x less useless. A few more such gatherings and the relevance of tracing drops to those sub quantum levels of homeopathic medicine.
There's other weird effects going on -- some countries that look really really similar have vastly different experiences with the virus. (Canonical example is DR and Haiti, although the situation is dynamic enough no-one knows if that'll last.)
My takeaway from the difficulty in measuring this thing is that there is pretty high variance in transmission. Some carriers spread it REALLY well. Some carriers spread it poorly. With a lot of variance it matters a ton to figure out what is the deal with high-transmission situations. My take so far is we have some clues but no certainty. (Seems to spread in public transit and healthcare environments more rapidly, but slower than you'd expect in schools and prisons.)
It'd clearly be a gigantic win in terms of intervention policy to understand this better, and we simply cannot do that without extensive contact tracing so we know what's going on. They're doing a pretty good job of this in China, HK, Taiwan, South Korea. As nearly as I can tell we're doing a dismally poor job in the US and Europe.
You read papers that have diagrams of restaurant tables and bus seating charts from China. In the US it's hard to get stats on aggregate nursing home vs non-nursing home fatality rates. Maybe it takes some time for these papers to come out, but I don't see evidence that high-quality pre-pub contact tracing data is being relied on to develop policy responses.
reply