The steady state is exactly 1, which is like balancing a pencil on its point.
It's plausible that two things happened here: the various local restrictions reduced the R0 of flu below 1, and the border closures kept mutations from traveling: and influenza is notoriously mutation-prone.
These can combine to practically extirpate influenza. Unfortunately, the effect is temporary, and the next flu season is likely to be a real doozy.
Which will be "fun" because our societies now have a hyperactive immune system, and there will be considerable political pressure to "do something" about the next flu wave. This must be resisted but I'm not optimistic.
In particular you could imagine that if people never venture outside their own block that the social network is an euclidean graph. In an ideal case where people are evenly spaced in the plane and only interact with neighbors, the disease would spread as a circle expanding outwards, so total infections would be proportional to ~ t^2, and current infections ~ t.
At exactly one, it's indeterminate; you could see a subexponential growth or decay. With no exponential terms remaining, lower-order terms that are ordinarily hidden by exponential growth become the dominant observables. (Since epidemic spread is also random, you're much more likely to see the stochastic terms show up in the overall statistics in these cases. You really can be lucky or unlucky with Rt ~= 1, but there's no persistent luck with Rt >> 1.)
This is also important before community spreading sets in, and it is the mechanism by which contact tracing can work. Rather than change the general susceptibility of the population to the disease (changing the effective reproduction number), contact tracing tries to operate at the level of individual cases in ways that cannot be scaled to uncontrolled community spreading (even if Rt is close to 1).
> and the border closures kept mutations from traveling: and influenza is notoriously mutation-prone.
Perhaps, but are influenza mutations an important effect within a single flu season? I know the determination of to-be-dominant strains has a great effect on the composition of each season's flu vaccine, but as far as I am aware we don't see declining flu vaccine efficacy over a season.
Over pretty much the last year you could observe, in different countries all around the world, that the reproduction number was 'magically' floating around 1.
Only recently did I learn that this effect was puzzling for epidemiologists as well and was only solved around 2012 (?) in a model that assumes a network of information about the disease in parallel to the network of disease transmission. The resulting feedback loops lead to the meta-stability of R=1. Super interesting how society acts as this distributed information processor, similar to 'the market' in economics.
You can almost see the phenomenon in real time during this pandemic. Countries that have low trust in authorities will still freak out when the epidemic hits biblical proportions, and do various forms of impromptu distancing measures which will bring the R number down. Then when the signs of panic subside, they'll loosen them. And so on.
Societies with high trust in authorities will still pressure their authorities to loosen up when things feel safe, with predictible results, leading to further lockdowns.
Then all of this will come back in the future and kick you in the teeth. Either we're going to have to accept this as a way of life, which is more detrimental. Or we're pushing off the inevitable.
This was uncertain to most people last year, but now we’ve seen so many examples that it really shouldn’t be so controversial any longer. But if it wasn’t, we wouldn’t be discussing it.
The covid virus is evolved to fit exactly into the niche of societal behavior where it will be a big fucking problem but not so bad that it’s immediately obvious to enough people.
Influenza is pretty promiscuous. In normal conditions, very few people aren't exposed to it: either their existing immune resistance (vaccinated or otherwise) is up to the job, or it isn't.
Mutation is therefore the primary driver of flu, year upon year. This is why vaccines are continually reformulated for a best-guess at what strains are going to be dominant.
We had just concluded a northern-hemisphere flu season when travel restrictions started to kick in. This was followed by at least a 90% reduction in international travel, and for most of what remained, it was mandated that new arrivals isolate for long enough to eliminate any influenza they might have carried.
Lockdowns would mean less mutation to begin with, since it happens in human hosts. And such mutations as did present are going to have a tough time jumping oceans, and even when they do arrive, spreading through the populace is substantially inhibited.
Ironically, the universal mask mandates are likely to be more effective against flu than against COVID. Like it or not, masking has minimal effect on spreading aerosols, although using a "real" mask, and being pretty careful to wear it right, can mitigate inhaling those aerosols.
Influenza is believed to be spreadable through aerosols, but the primary vector is droplets, while the opposite appears to be true for SARS2. Bog-standard cloth masks are fairly good at keeping droplets off people and surfaces.
https://www.pennmedicine.org/updates/blogs/penn-physician-bl...
> The principal mode by which people are infected with SARS-CoV-2 (the virus that causes COVID-19) is through exposure to respiratory droplets carrying infectious virus.
https://www.cdc.gov/coronavirus/2019-ncov/science/science-br...
From what I can tell, you may have your flu/covid mixed up. Covid is spread through respiratory droplets, the spread of which is reduced by wearing a mask.
The claim that "lack of infection spread in hospital settings" rules out airborne transmission due to masking is also questionable. The opposite seems true. As I understand it, infections in hospital settings have been routinely documented throughout the pandemic despite masking, contact protocols, etc. - which implicates airborne rather than droplet/fomite transmission.
This is a really good article in the Lancet recently which solidified my opinion on this. It offers 10 items of evidence for airborne transmission being the primary driver of the pandemic.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
For me, the key points are:
> Second, long-range transmission of SARS-CoV-2 between people in adjacent rooms but never in each other's presence has been documented in quarantine hotels.7
> Sixth, viable SARS-CoV-2 has been detected in the air. In laboratory experiments, SARS-CoV-2 stayed infectious in the air for up to 3 h with a half-life of 1·1 h.12 Viable SARS-CoV-2 was identified in air samples from rooms occupied by COVID-19 patients in the absence of aerosol-generating health-care procedures13 and in air samples from an infected person's car.14 Although other studies have failed to capture viable SARS-CoV-2 in air samples, this is to be expected. Sampling of airborne virus is technically challenging for several reasons, including limited effectiveness of some sampling methods for collecting fine particles, viral dehydration during collection, viral damage due to impact forces (leading to loss of viability), reaerosolisation of virus during collection, and viral retention in the sampling equipment.3 Measles and tuberculosis, two primarily airborne diseases, have never been cultivated from room air.15
> Seventh, SARS-CoV-2 has been identified in air filters and building ducts in hospitals with COVID-19 patients; such locations could be reached only by aerosols.16
> Eighth, studies involving infected caged animals that were connected to separately caged uninfected animals via an air duct have shown transmission of SARS-CoV-2 that can be adequately explained only by aerosols.17
> Tenth, there is limited evidence to support other dominant routes of transmission—ie, respiratory droplet or fomite.9, 24 Ease of infection between people in close proximity to each other has been cited as proof of respiratory droplet transmission of SARS-CoV-2. However, close-proximity transmission in most cases along with distant infection for a few when sharing air is more likely to be explained by dilution of exhaled aerosols with distance from an infected person.9 The flawed assumption that transmission through close proximity implies large respiratory droplets or fomites was historically used for decades to deny the airborne transmission of tuberculosis and measles.
[citation needed]
Why on earth does it make sense to resist sensible public health measures to reduce the influenza to R0<1?
The measures would not need to be nearly as drastic as those for COVID ("normal" R0 of 2 vs 2.5+), so more handwashing (good to minimize a broad spectrum of pathogens), masks (already culturally ordinary in many countries), and especially better indoor ventilation systems would be a long-term benefit to everyone.
I'm mostly hoping that the success of better sequencing, mRNA vaccine technology, and the rapid development deployed for CV-19 will also be applicable to influenza and help minimize or practically eliminate it.
Are you assuming other measures?
Obviously your quoted poster’s concerns are less about “hand washing”, “wear a mask if you have symptoms”, and “stay home” while you recover, and instead are about an overreaction in which entire businesses are forced to shut down, children without symptoms are forced to wear masks even as they run and play, and people are forcibly prevented from leaving their homes “just because it’s flu season”.
This may be necessary, at times, for COVID-19, but as you recognized, not for the normal flu.
Given the spotty record of both public and private policy with regards to using actual science as a driver, these are not invalid concerns.
Or put differently, rather than presuming that anyone against “doing something” is against “common sense” measures, perhaps we should be supportive of making sure that we do something, AND that the “something” that we do remain in the realm of common sense, to assuage the very real concerns that “doing something” could mean something more harmful than good.
If I (salaried) take a sick day, I get paid the same amount from the same source; there’s next-to-no economic incentive for me to risk the health of others by working when sick: problem is solved.
We could more or less force the same by law for scheduled hourly workers. It’s a little more difficult for gig. It’s basically impossible (as I see it) to put self-employed people at the same outcome as if they worked without substantial risks of under-comping some and over-comping others.
That is to say most people don't have allergies to confuse with illness and although you might wake up feeling poorly for a number of reasons flu sufferers are liable to suffer from one or more distinguishable symptoms for example for myself when I've contracted the flu I always get a really shitty body ache.
It's possible to get a cold without also having a fever. You are absolutely correct about that but even in that instance the majority are liable to be able to know when they are ill. They just don't stay home because the social pressure has been in favor of bringing your sickness to work as if you were doing everyone a favor by showing up and making your cohorts sick.
Sometimes my throat is sore but its just allergy drainage. It doesn't help that the things I'm allergic to line up with flu season.
https://www.aaaai.org/about-aaaai/newsroom/allergy-statistic...
https://acaai.org/news/facts-statistics/allergies
1 Hay fever, or allergic rhinitis, is a common condition with symptoms similar to those of a cold. There may be sneezing, congestion, runny nose, and sinus pressure. It is caused by an allergic response to airborne substances, such as pollen.
2 The American Academy of Allergy, Asthma & Immunology (AAAAI) is the most prominent membership organization of more than 7,000 allergists / immunologists (in the United States, Canada and 72 other countries) and patients' trusted resource for allergies, asthma and immune deficiency disorders. This membership includes allergist / immunologists, other medical specialists, allied health and related healthcare professionals—all with a special interest in the research and treatment of allergic and immunologic diseases.
WebMD's doesn't actually seem to actually source their data at all despite styling it like a link for some reason and since their is a disparity between what the CDC and AAAAI say I strongly suspect they are full of shit
Depends on what you want to achieve. If you like a increase of infection, you do it like here in germany and close down hardware stores etc. multiple times on short notice, without telling when they will open again - so people try to storm them before they close, all coming closely together by doing so, which they would not have otherwise.
For example here in order to avoid contamination in public transports they limited the hours of service. Consequence: same number of people took transport but in less time, increasing density and contact.
Similarly with the curfew forcing shops to close earlier in the day, more people gather in less time.
We've sorted a lot of this out over the past year, but there is an all time distrust of institutions surrounding both policymakers and the public health recommendations informing them, and there's a reason for it.
We can either help assuage people's fears (whether you see them as founded or unfounded) by empathizing with their concerns and experiences and addressing them while ensuring that any measures enacted remain rooted in science that we can trust...
OR we can be part of the problem for why there's so much distrust, by ignoring anyone who may have real experiences that have caused them to lose trust in our science and health institutions, and telling them that it's all in their head.
I strongly hope for the former, myself.
- Paid sick leave. First and foremost.
- Increased flexibility for people WFH as possible if sick or vulnerable.
That's really about it. Maybe masking, though that well has been throughly poisoned.
Well, yeah, they can be asymptomatic, spread their sickness to other kids, who then take it home to their parents and grandparents.
Public health measures that you disdain aren't popular where they are because your neighbors want to step on your neck they are popular because people who know more than you do know they on net save lives.
When there is nothing to be gained by such measure support will blow away like dust in the wind. There is no battle for you to fight.
If anything, politicians have vastly under-managed the situation, timidly afraid of offending constituents' offense at any inconvenience, and only partially at best following sound science.
In states that did issue orders for masks and stay-at-home, the orders were weak, late, and lifted early, resulting in multiple waves that only abate now because of the rapid deployment of vaccines.
Most importantly, there was very little and late funding to cover the costs of those who should most have been shut down, group travel, entertainment, dining, etc. - should have been fully shut down immediately, and everyone's costs covered.
6-10 weeks of hard shutdown, while standing up a full masking, test/trace/isolate protocol would have handled it, yet few countries did it.
A few countries did implement early, strong, and effective measures, such as New Zealand. They also then opened up many months earlier than the rest of the world with near-normal life.
Where are the politicians "drunk with power" who are restarting lockdowns for their own gratification?
Where is the advantage for such a "drunk on power" politician? What could they possible gain by unnecessarily implementing measures that are seen at best by the smart ones who understand it as a necessary inconvenience, and by the rest as an assault on them?
Even flat-out authoritarians do no such thing. E.g., China, who is unashamed to run literal concentration camps for Uyghur minorities, and who did hard lockdowns at the start, is not opening up as soon as scientifically feasible.
Unless you can show some citations of evidence, this looks a lot less like a real phenomenon, and more like a pseudo-libertarian teenager's trope.
Let's not forget a substantial portion of the population working from home, using less public transportation (choosing to travel by car when traveling at all), a huge decrease in tourism and large public gatherings, much less eating out at restaurants, contactless food delivery becoming the norm, etc.
So many factors figure in to why much of the (wealthy, developed) world is a lot more resistant to contagious pathogens today than it was a year ago.
“Exponential with R varying over time” and “not exponential” differ only in interpretation imposed by an observer.
> infection is simply an exponential process
No, in the hyperidealized perfect mixing scenario, its a logistic process, like most other resource constrained processed that look exponential when analyzed over a dhort period.
In the real world, its neither exponential nor even perfectly logistic, even before considering changes to the environment in which the disease spreads (including those induced by the disease, including people’s response to knowledge of it.)
So, do something by taking a flu vaccine like is already available and recommended for annual use by the CDC?
[0] https://www.cochrane.org/CD001269/ARI_vaccines-prevent-influ...
The difference in measurement is small, relative to the error in measurement.
Look at the error bars on the R0 estimates in that paper. Influenza runs from 1.06 to 3.4. You are trying to make micrometer inferences from a parameter where our best estimates are measured in libraries of congress.
If you consider the influenza estimate independent of equivalent estimates for covid, then there's a substantially greater than 50% chance that influenza's R0 is meaningfully smaller than that of the flu. If the estimates are partially dependent (i.e. methodology that gives a larger estimate for influenza would also give a larger estimate for covid), then that chance goes up further.
Moreover, we also have evidence in the actual observations of epidemic dynamics. Over the southern hemisphere fall of 2020 (northern hemisphere spring), covid cases increased more rapidly than influenza cases in countries that were entering their flu seasons. That's compelling-to-me evidence that covid in fact has a larger basic reproductive number, whether that be due to a fundamental difference in the virus or just the effects of low baseline immunity.
Now, your idea that the particular set of policy restrictions may be more effective against influenza than covid is very interesting. There's a basic horse sense to it, as well, since policymakers were largely operating from a playbook written for a flu pandemic. However, I do not think that "more effective" is a necessary component of the argument; "at least as effective" will do just as well given influenza's low baseline prevalence (out of season).
Remember, my original point upthread was not to explain every bit of the relative epidemic curves, but instead to claim that we really ought not be surprised by the difference. I see little need to resort to specialized theories to explain the broad outline, even though I'm sure they will be helpful in the details.
Yes, we know that SARS-CoV2 increased, and influenza went away. That's trivially observed. We don't know why flu went away.
To turn that observation around and say "Covid grew faster than flu, and therefore it has a higher R0, and therefore, the flu went away because {insert your favorite NPI} was just good enough to stop it" is begging the question.
It could just as easily be any number of other factors that you're not accounting for. There's also a number of other faulty assumptions inherent in your logic. For starters: there's no particular reason, a priori, that a person couldn't have both flu and SARS-CoV2 in the same year.
> I have seen no credible evidence that typical (non-pandemic) influenza has an R0 greater than that of SARS-CoV-2. If you have a citation handy to the contrary, I'd be interested in seeing it.
Even if the difference in R of influenza and SARS-Cov-2 was only 0.1 (and there is no evidence suggesting the average difference is that small) and assuming both pathogens spread in a similar fashion [1], then over time SARS-Cov-2 will fluctuate around the meta-stable point of 1.0 and as a result influenza will decrease exponentially.
[1] https://virologyj.biomedcentral.com/articles/10.1186/1743-42...
Trying to use this tiny relative difference in fuzzy estimates of empirical parameters to make a complex causal arguments about...well, anything...is folly.
If there are no studies to show, refer to an opinion of an epidemiologist or any other expert in the spread of infectious diseases.
You seem to argue against a vast field of computer scientists, mathematicians, physicists, biologists, medical experts that do nothing else but study the spread of infectious diseases.
Burden is on the parent to prove their claim, not for me to disprove claims advanced without evidence.
All current estimates for R0 have wide, overlapping confidence intervals that make it impossible to differentiate them from other viruses. The best anyone can say is that Covid and influenza have similar mean R0 estimates.
> If there are no studies to show, refer to an opinion of an epidemiologist or any other expert in the spread of infectious diseases.
I cited just such a paper. Please refer to it.
Multiple people have cited many papers that all generally agree with the trend that influenza has a lower r0. You've discounted those by making what are ultimately statistically unsound claims.
> I cited just such a paper. Please refer to it
The paper you cited supports the other person's contention: that r0 of influenza is lower than that of covid.
As "the other person[1]," I'd like to point out for the sake of accuracy that the paper you mention here does not in fact study covid. While published in February 2020, the "SARS-CoV" it talks about was SARS 1, not the virus behind the current pandemic.
I've taken my prior for covid's R0 from sources such as the CDC (https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scena...), which seem to report a best guess of about 2.5 with some room for variation.
[1] -- Who is also leaving the argument. We've both made our points well enough for others to form their opinion, and I don't think there's much unexplored territory.
Next year it is entirely possible that the R0 of covid drops below influenza.
If you introduced influenza to a naive population (i.e. native americans) you would get massive death.
<<Experts believe that as much as 90 percent of the American Indian population may have died from illnesses introduced to America by Europeans>>
any info about this? very interesting
Europeans brought deadly viruses and bacteria, such as smallpox, measles, urope. Europeans brought deadly viruses and bacteria, such as smallpox, measles, typhus, and cholera, for which Native Americans had no immunity (Denevan, 1976). yphus, and cholera, for which Native Americans had no immunity (Denevan, 1976). On their return home, European sailors brought syphilis to Europe. Although less n their return home, European sailors brought syphilis to Europe. Although less deadly, the disease was known to have caused great social disruption throughout eadly, the disease was known to have caused great social disruption throughout the Old World (Sherman, 2007)
https://www.kellogg.northwestern.edu/faculty/qian/resources/... (Note that I haven't read this whole thing, but wanted to find a source for my little factoid)
Europeans successfully domesticated animals, Native Americans did not. So Europeans had diseases that Native Americans were not adapted to.
See the wiki page: https://en.m.wikipedia.org/wiki/Native_American_disease_and_...
Given the reproduction number appears as the base of an exponent, I would not consider the difference "small."
If influenza has a typical R0 of about 2, reducing contacts by 50% would make its growth non-exponential. If covid has a typical R0 of about 2.5, doing the same would require a further 20% reduction of contacts, to 40% of baseline rather than 50%. Since population behaviour and legal restrictions have diminishing returns (eliminating casual contacts first at lower cost, then progressively higher-cost and more essential contacts), this could easily correspond to a large difference in effected (necessary) policy.
> Second, R0 is an estimated value. There are big error bars on all of these estimates -- the overlap is far greater than the 0.5 you're using to claim causality.
I have seen no credible evidence that typical (non-pandemic) influenza has an R0 greater than that of SARS-CoV-2. If you have a citation handy to the contrary, I'd be interested in seeing it. In the meantime, I tried to be generous in my estimation of influenza's R0; even your reference [2] places its central estimate at 1.68.
> Third, rhinovirus has not gone away (estimated R0 < 2). Nor has adenovirus (estimated R0 ~2.3) [1,2]
Rhinovirus and adenovirus both have mean-estimate R0 greater than that of influenza in your reference [2], so if policy is going to eliminate any of these disease from general circulation then influenza would be the first.
Furthermore, some analysis does show limited evidence of a reduction of rhinovirus cases (https://www.nature.com/articles/d41586-020-03519-3). A confounding factor here, however, is that we don't really have comprehensive like-against-like monitoring for rhinovirus in the way developed nations monitor for influenza. Adenoviruses as a broad category are also not limited to respiratory transmission, so air-focused restrictions would have less effect on these other routes.
Finally, I reiterate that flu has a pronounced seasonal variation, whereas rhinovirus is somewhat less variable. A set of social responses only needs to prevent the flu season from starting to make it "disappear."