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COVID-19 Coronavirus: facts and science

thomas

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This thread is reserved for updates on scientific news and research relating to COVID-19 and SARS-CoV-2 (scientific articles and interviews with specialists working in epidemiology, virology, and other related fields).


Please do not discuss any issues related to COVID-19 here, but proceed to one of the following threads:



 

johnnyG

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For some reading on the 1918 flu. Both the initial link and many of the comments are good:

 
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"There is some limited evidence that school closings do reduce seasonal influenza transmission (Heymann et al., 2004), and it is assumed—although but not proven—that other limits on social mixing also slow the spread of respiratory disease (World Health Organization Writing Group, 2006). Thus societies faced with pandemics have often closed public places (schools,8 childcare, workplaces, mass transit) and cancelled public events (sports, arts, conferences). "


Schools are absolutely ideal for disease transmission - many people in close proximity, with underdeveloped immune systems (young people haven't been alive long enough to have been exposed to many seasons of virus variations), and of course, getting young people to follow best hygiene practices is even harder than with people in general. While those young people will have to be somewhere and continue to pose some risks, they are unlikely to be crowded together in equally large numbers while schools are closed.

I don't disagree that the school closings appear to be poorly planned and executed, and will put a sudden and unexpected burden on many parents... but they aren't a pointless gesture either, and are in fact, fairly standard practice.

I think permanent containment is impossible, but slowing the spread of the disease will spread out the stress on the health care system as the disease works its way through the population.

if you would get a fever and a cough in the upcoming days, would you go to the doctor?

Honestly, you should not if you don't have severe symptoms and are not part of a vulnerable population. For healthy people, it's likely just a severe cold, and the health care systems are going to be severely stressed. That said, pneumonia can be dangerous and is best treated early, so if you are having breathing difficulties then by all means seek help, regardless of the level of your fever or how good your health normally is.
 
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a virus that kills about 2% of the people it infects.

Dr. Fauci et. al's editorial is widely accepted in the medical community. It is not, of course, in and of itself a study but it is a commentary from experts in the field on how to understand the real implications of the raw data that we have.

"If one assumes that the number of asymptomatic or minimally symptomatic cases is several times as high as the number of reported cases, the case fatality rate may be considerably less than 1%. This suggests that the overall clinical consequences of Covid-19 may ultimately be more akin to those of a severe seasonal influenza (which has a case fatality rate of approximately 0.1%) or a pandemic influenza (similar to those in 1957 and 1968)"

 
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I mean how much mutation is enough that they can detect before they start labeling it as a different strain? At what point do your antibodies no longer fight a new mutation?
This is actually all very heavily studied already. Remember that coronavirus is responsible for much of the common cold as well as SARS and MERS. It's true that it is very likely to mutate... it's hard to find articles right now because of the news cycle dominating the search results, but as I recall, it's roughly 2-4 years before a strain fades away. Part of that is herd immunity (enough people have become immune that the old strain has trouble propogating) and part of it is mutation rate. Mutations are constant in cold and flu viruses, which is a significant part of why we haven't just eliminated them like we did with smallpox. Also, of course - partly because of the mutation rate - there are a *lot* of strains out there.

Anyway, the COVID-19 virus will certainly mutate, but then it won't be the COVID-19 virus anymore - it will be another coronavirus (more accurately, many coronaviruses; every time the virus duplicates, in every infected person, everywhere in the world, there is a small chance of a mutation, some of which will result in viable new strains).
The new viruses may not cause pneumonia anymore. If one or more does, we'll have to deal with that then... but chances are good that any strain different enough to fool our immune systems has also mutated back into just being a cold.

Some of the difficulties in creating a vaccine for the virus are discussed here, as is the risk of mutation, but it doesn't directly address all the concerns we're discussing here.

 
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Wiki says the only current pandemic is AIDS and the most recently ended pandemic was H1N1. Are they just slow to update?

The wiki also notes,

In February 2020, WHO spokesperson Tarik Jasarevic clarified that, "there is no official category (for a pandemic)... For the sake of clarification, WHO does not use the old system of 6 phases — that ranged from phase 1 (no reports of animal influenza causing human infections) to phase 6 (a pandemic) — that some people may be familiar with from H1N1 in 2009."

At this time at least, "pandemic" is a lay term and not an official term, and it simply means, more or less, "a world-wide epidemic."

COVID-19 is at 4 out of 4 on the WHO's current scale that doesn't use the word "pandemic", that has replaced the 6-step pandemic scale. As such, it doesn't seem unreasonable to call the current outbreak a pandemic, although reasonable people could disagree about whether we would be at stage 5 or stage 6 of the old scale.

Normal colds aren't considered "pandemic" simply because one is so similar to the next that they are considered "endemic", as your quote suggests. If you tracked each individual cold virus I'm sure many of them would be pandemics, but because they are grouped together as one disease, that's not how they are counted. HPV also is of course "endemic" and so disqualified from "pandemic".

I'm not sure HIV can be considered "pandemic" anymore but maybe there are still large parts of the world where it is still spreading. It seems to me it's closer to the definition of "endemic".

Are they just slow to update?
They had included COVID-19 as a pandemic, but it was reverted with this reason given, "The World Health Organization has yet to classify coronavirus as a pandemic. Until they do so, it remains a possible pandemic. "


Of course, as had already been stated and recorded in the wiki article, WHO doesn't use the term "pandemic" anymore, so this reasoning is dubious. At any rate, until all the editors understand that WHO will no longer be using the term pandemic and settle on a new criteria, there won't be any new pandemics listed.

Wikipedia is very fast to update uncontroversial statements, but anything controversial (like calling something a "pandemic" without a published reference or official statement) is going to get reverted. You cannot add to the list of pandemics based on the definition of pandemic either -- Wikipedia doesn't allow "original research", so you must find a source that has called it a pandemic and convince anyone who disagrees that your source is more authoritative than their source. With long-term disagreements with many sources on both sides, sometimes both views are presented, but it all becomes very political at that point. (Political in the sense of the type of human interaction, not in the sense of partisanship.)
 
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But this is extra special "new" and extra special "easily transmitted" well I need some clarification on that.
your site says:
Because SARS-CoV-2 is new to humans, everyone is assumed to be susceptible.

This refers the extra-special "newness" of the virus.

It's not a minor mutation of an already endemic strain that is close enough to be recognized by our immune systems; normal seasonal mutations are easily adapted to because they closely reasonable minor seasonal mutations of previous seasons. There are of course bad cold and flu strains, where either a mutation is difficult to adapt to or a strain that was never previously widespread starts to spread. Anyway, there is currently no evidence that we have any pre-existing resistance to this virus, and it is believed that we most likely don't.

As far as "easily transmitted," I think you're completely on-point here. I have yet to see anything substantial that suggests that it is any more or less contagious than the average cold-causing coronavirus, or spread in any way that is substantially different. All the comparisons that show that it is "more easily spread" do seem to be comparing to the flu.

WHO finally decided to call it a pandemic [...] anyone else think this is more politics than medicine?

Changing their scale for track world-wide disease spread to not include the word "pandemic" and then coming out now to declare it a "pandemic" are both clearly PR moves. It's not unreasonable to consider that some kind of politics.

Personally, I just consider it an egregious PR misstep. They seem to have wanted to remove the word "pandemic" from the lexicon entirely, but of course removing it from their official descriptions of stages of an epidemic doesn't take the word out of the conversation. Saying "we don't use that word" is essentially ignored. (Technically that's a quote from the CDC not the WHO, but they have been on much the same page in this attempt to get people to stop using the word 'pandemic'). I understand that "pandemic" is a scary sounding word and they don't want panic, but the natural result of not using the word was always going to be reflected in the press as "a pandemic hasn't been declared yet" and was never going to be for the press or the population to stop using the word altogether.

The disease has in fact met the ordinary definition of a pandemic for some time now, but many media outlets at least, and probably other public-facing persons and organizations as well, have been refusing to call it a pandemic because the WHO hadn't "declared" a pandemic yet. Today's declaration was almost certainly simply to end the inconsistency between the actual meaning of the word "pandemic" and the official descriptions of the disease.
 
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The difference between the common flu and Covid-19 is the difference between 1.3^10 and 3^10: 59,000.

That is some important math. The infection rate is so high not only because COVID-19 is highly contagious, but also because there is apparently no pre-existing immunity.

However, it's a very simplified story.

Assuming those base numbers are correct, it's more accurate if less dramatic to say that it's 1.3^X vs. 3.0^X, where X is the number of times the disease has been spread by current carriers to new patients. That simplified model (accurate only for initial spread where the base infection rate stays the same) looks like:

Generations:123456789101112131415
1.3^X1.692.22.863.714.826.278.1610.613.7817.9223.330.2939.3751.1966.54
3.0^X927812437292,1876,56119,68359,049177,147531,4411,594,3234,782,96914,384,90743,046,721

That shows the idea of why it spreads so fast, but it's not a strictly accurate model.

'X' is approximately the same as incubation period+illness period, although in practice disease don't propagate in discrete generations like a simple computer simulation (epidemiologists do more complex math to account for that, of course). Also there is probably a couple days early on where you are incubating but not yet contagious.

Also, in real epidemics the base number shrinks as the epidemic grows. The real number of new cases is not (# of exposures * infection chance), it's (# of exposures * (infection rate - "already sick or immune" proportion). Once 57% of the population already is or has been sick, the remaining spread will look like the beginning of a seasonal flu epidemic. Once more than 67% of the population has already been sick the base new infections (# of exposures * (infection rate - "already sick or immune" proportion) will be less then 1, and the total number of cases will start to shrink.

Of course, governments are also trying to reduce the infection rate by reducing the number of exposures. Where they succeed the virus could be contained before it naturally fades out. At least it will slow the spread dramatically for relatively modest success in reducing the number of exposures (you could work out a similar table
for e.g. 2.5^X to approximate a modestly successful exposure reduction, or whatever base number you believed would be the result of a given policy.)
 
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For those interested in the math behind epidemic numbers and the effects of various strategies and behaviors on those numbers, 3Blue1Brown spends some time time simulating various epidemic models, doing a great job of explaining and illustrating in detail some of the math we were discussing earlier as well as touching on some topics that we haven't discussed in relation to those numbers. He covers travel between communities, travel to a central location, quarantine, social distancing, and various rates of transmission.

Simulating an Epidemic:

Philip Defranco managed to get an interview with Dr. Fauci. The doctor is much more clear and informative in this relaxed setting than he is under the stress of facing the white house press corps. The entire interview is worth listening to, IMO, however in particular he addresses the question of re-infection.

Re-infection question timestamp:

Whole video:
 

thomas

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Interview with Professor Kim Woo-Joo from the Korea University Guro Hospital. Over the past 30 years, Prof Kim has dealt with infectious diseases such as tuberculosis, AIDS, measles, SARS, swine flu (2009), Ebola (2014), and MERS (2015). He describes the current COVID-19 pandemic as the most challenging.

 

thomas

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According to an Australian study, the new coronavirus may remain infectious for weeks on banknotes, glass and other common surfaces.

Scientists at the Australian Centre for Disease Preparedness showed SARS-CoV-2 is "extremely robust,” surviving for 28 days on smooth surfaces such as glass found on mobile phone screens and plastic banknotes at room temperature, or 20 degrees Celsius (68 degrees Fahrenheit). That compares with 17 days survival for the flu virus. Virus survival declined to less than a day at 40 degrees Celsius on some surfaces, according to the study, published in Virology Journal. The findings add to evidence that the COVID-19-causing coronavirus survives for longer in cooler weather, making it potentially harder to control in winter than summer. The research also helps to more accurately predict and mitigate the pandemic’s spread, the scientists said. "Our results show that SARS-CoV-2 can remain infectious on surfaces for long periods of time, reinforcing the need for good practices such as regular hand washing and cleaning surfaces,” said co-author Debbie Eagles, the center’s deputy director, in an emailed statement Monday.

 

thomas

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So SARS-CoV-2 can survive 28 days on smooth surfaces (see above) and, according to a study of Kyoto Prefectural University of Medicine, up to nine hours on human skin, five times longer than the flu virus. Keep washing your hands!

 

Lothor

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I saw that on the news today. They also reported that alcohol destroys the virus in 15 seconds. Time to pull a cold one from the fridge!
 
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