Has anyone argued that?
Because that’s not what I have been saying. I have been saying that the chance of a newly emergent virus becoming more virulent is greater than the chance for an established virus. It’s a comparison between two values.
If I had to WAG ballpark numbers, I’d guess the chance of influenza mutating a substantially more virulent strain in a given year is of the order of 1/100 and for a newly emergent virus something like 1/20 for the first year and then basically 1/100 after that.
And the blog you cite seems to have made a similar error, in that he is responding to someone raising the possibility of a dangerous new strain mutating by saying “[outbreak-associated mutations] do not have to increase viral replication or virulence”. Well obviously not. But that’s not what the Vice Minister said.
The reason newly emergent viruses have a greater risk because of the very different selection pressure on a newly emergent virus. I’ve given cites not only of the principles but of the objective fact that many recent virus outbreaks have indeed mutated to become more contagious within months I won’t rehash the arguments again.
I didn’t say that. I said the mechanism of adaptation by natural selection is differential death. Yes, I was speaking to a narrow point - the fact that a highly virulent phenotype may not ultimately be adaptive for the virus is not necessarily what’s important, since the effect on humans during the process of natural selection against that phenotype may be devastating.
And what I am saying is that, if anything, the exact opposite is true. By far.
Going from low virulence to higher virulence through a new mutation given the numbers of influenza viruses out there happens every so often. See H1N1 a few years back. It will happen again and is a reason for huge concern.
Going from a state of maladaptive relatively higher virulence (because in new species and not yet selected for more “fit” lower virulence) to more fit lower virulence is OTOH fairly likely, given enough mutation opportunities to select from. OTOH even with lots of opportunities, trending to the less fit state, and farther from the mean for the viral family, is improbable. A novel to humans virus is most likely at its most virulent as it crosses over and decreases from there. A less virulent virus though may cause many more deaths than a more virulent one … potentially a much higher n to work on.
Reimann, obviously agreed to that second narrow point but it wasn’t the narrow point under discussion.
If we assume that in general lower virulence is better for the virus, then yes, on average viruses will tend to become less virulent over time. But you’re looking at this only from the perspective of the evolving virus, and again - that isn’t necessarily what matters. What matters is the probability that a dangerously virulent mutant phenotype will arise, and what effect that will have on the human population.
The virulence phenotype for a virus depends on how well the human immune system is able to cope with it. At the same mutation rate, my a priori expectation would be a much higher variance in virulence phenotypes for a novel virus that the human immune system has never been exposed to in any prior form. Higher variance implies a higher probability for a mutation with the optimally worst possible level of virulence for human fatality. Sure, there might be strong natural selection against that phenotype from the virus’s perspective, reducing its virulence over time - but that natural selection that would be carried out by killing a vast number of hosts.
I’m open to seeing data that proves my a priori expectation wrong, of course. But I’m not convinced by your argument on theoretical grounds.
Used carefully and properly… yes, they can reduce the spread of some illnesses, particularly if they are worn by the person with the sneezing/coughing/runny nose, capturing mucus and droplets of moisture.
Used improperly, they can actually become a vector for transmission - you have to handle something that is potentially contaminated carefully, and then carefully wash your hands afterward.
The news coverage is really not helpful here. Does a day-by-day count of “number of infected” and “number of deaths” really tell the laymen in the Western world anything meaningful at all?
I mean … no one really expects the virus to be contained to just a few tens of thousands worldwide and only kill, say, 1,000 people and then just STOP. Right?
The Trump administration on Friday declared a public health emergency over the coronavirus outbreak and said it would take the extraordinary step of barring entry to the United States of foreign nationals who have traveled to China.
Not sure my wife is going to be able to fly to the US on 5 Feb as planned on Delta. She’s a green card holder
Yes, the figures do give some information, like that the death rate is not going up, meaning original estimates of how deadly this infection is are correct. Number of new infections can give an indication of whether or not containment tactics are effective (effective does not mean new infections stop immediately, of course). In a week or two we’ll be getting more information on average length of illness, how rapidly people recover, and so forth.
Laypeople will not get as much useful information as experts, but these statistics are not meaningless.
The SARS virus did more or less what are describing - it infected about 8000 and killed about 1000, iirc.
This virus seems to spread more easily from person to person, but to have a lower death rate. The inverse relationship is what you would expect - an individual infected with a really deadly virus won’t be going out and about infecting people.
There is of course no data supporting your a priori expectation … nor any explicitly disproving it. I really am open to seeing data that proves my expectation wrong as well.
Still I’ll try this argument on you:
The conditions that led to SARS, 2019 nCoV, and MERS, are not new in the past two decades. One reasonably presumes that coronoviruses have crossed over from animals many times in the past, likely with the same frequency of maybe once or twice a decade.
What can we learn from the historic past epidemics caused by these novel coronaviruses crossover events?
Mainly that they never occurred, at least to any degree that was noticed as other than background noise in the crush of other viral illnesses. No doubt some had some virulence on crossing but we have no Spanish Flu sort of coronavirus event known in history.
If your a priori assumption was correct we should have had quite a few. Why have we not?
No question that the modern world with global travel amplifies risks. The serious containment efforts are very warranted. The reality of a new virus with even a 0.2% … or less … mortality rate, spreading quickly across millions, is scary enough. But there is NO reason to think that this virus is at any greater risk to become increasingly virulent than established viruses have, and every reason to believe the opposite.
I would be leary of comparing infection rates vs SARS. Reporting during SARS was not nearly as complete or timely as now. I had a dorm friend from college that worked for the CDC in China, and went into hot zones of the break out. They found dozens of peasants that had symptoms or had recovered, but were not officially reported because there had not been definitive testing done on them. The local officials wouldn’t report someone with pneumonia like symptoms if they had not been officially tested and diagnosed. Net net, if you had crappy reporting during SARS (which is generally accepted) and decent reporting now, there will be a big gap.
It looks like she needs to fly to another country first and stay there for 14 days and then fly to the U.S. [the restriction is to foreign nationals who have traveled to China in the last 14 days]
Keep in mind that there’s a group of nearly 200 American citizens now under a 14 day quarantine when originally they were told 3 days. Not saying that’s going to happen to her, but it might be a good idea to keep travel plans flexible.
I’d also say limited info, rather than ‘not helpful’. Dividing deaths so far by confirmed cases so far early in an outbreak is not really the answer to the question the layman is probably asking: ‘how likely is it you die if you get this disease?’. Because on the bright side people with mild cases (of a disease that can be mild as appears possible with this one) aren’t all included in the denominator. On the darker side, those among confirmed cases who’ve died so far aren’t necessarily all those among currently confirmed cases who’ll eventually succumb.
The ratio of deaths to cases when SARS was spreading was significantly lower than the % of people who eventually died divided by those eventually counted as having had it, so I don’t think you can directly compare the backward looking SARS ratio to the current one for this disease. The other statistical thing though is that in a place like China (as opposed to very poor countries with very weak public health systems in case of Ebola say) almost all the deaths will eventually be counted and accurately allocated to the disease. But many people who had mild cases may never be counted.
You cay say based on the public numbers that it’s not a disease like Ebola to use that example again. It seems to me less certain to compare the danger to after-the-fact counts of total deaths divided by total cases for say SARS, or a given year’s ‘normal’ flu even. As the debate above also notes, the threat is a composite of % likelihood of dying if you get it and how easy it is to communicate the disease and how hard to screen people to reduce transmission (if it can be spread by asymptomatic people as seems to be the case there, though symptomatic people might still be the main conduit).
If you need to pass on information, SciShow (YouTube) posted a video update on what is know about novel corona on 1/31/20. It’s a few days, at least, out of date, but the basics sound pretty good. They still don’t know which animal was the vector.
I was unaware that the genome has been established and shared between countries. Or that the first known cases occurred were 12/31/19. Governments and agencies are showing a fast response.
