Delta is less deadly because more people have some immunity, either because of vaccination or because they have already been infected. Also it came late in the game, and many of the people who are the most at risk are already dead. Treatment has improved too.
So the virus itself isn't less deadly, it is just that we are better prepared.
Is Delta more deadly? I thought that was not really believed to be the case any more, just that it is much more transmissible. I could totally be wrong though; it's hard to find reliable info.
Evidence suggests Delta may actually be slightly more lethal, all else being equal. But all is not equal, a lot of the most vulnerable folks are either dead or vaccinated now.
the relative deadliness of delta... we'll just not ever really know. Though IIRC, some early surveillance with all the controls (only looking at unvaccinated, etc) suggested that it was LESS deadly for the elderly, more deadly for other age groups, net less deadly.
the delta is even less virulent then past variants. it's only marginally more lethal than the flu. long covid is a fuzzy excuse to prolong the panic culture.
Fortunately this is the trend for most viruses. I have seen no evidence that the delta variant was more lethal, but that it was more transmissible. I have also seen numbers from my locality sequencing that suggested lethality was significant chunk less than that of alpha.
I suppose it depends on how you calculate it. If the delta variant is equally deadly to previous versions (to an individual), but is more infectious, then more people will die, all else being equal. More people dying --> more deadly, at the population level.
Delta is more infective than Alpha. The mortality rate is comparable if not worse, but it's hard to say as we've had extensive vaccination, which has made it hard to assess. We're lucky for the moment with Omicron, but there is no guarantee.
The design space for diseases are large, and there is no guarantee what happens next. Maybe the next variant is even less lethal, but leaves 90% of people with long term damage. Maybe the next variant is far more lethal, but has a much longer prodromal period with allows it to infect far more people. Maybe we get a variant which is a little less lethal, but persists on fomites for far longer, so it becomes harder to avoid.
The general idea that diseases become less virulent over time is a misinterpretation. Diseases populations and hosts populations co-evolve. Over time, those who are more likely to die from the disease fail to reproduce. Only the most resistant offspring are left in the population.
The rabbit disease myxomatosis killed 90% of rabbits when it was introduced to Australia. Today it kills less than 10% of rabbits. However, myxomatosis is not less virulent.
Lab rabbits have been isolated from natural selection pressure for a very long time. When exposed to today's "mild" myxomatosis the disease still wipes out 90% of them.
The long-term trajectory of our species's co-evolution with covid-19 probably results in fewer of our offspring dying from covid-19 in a hundred years, but that means squat to those of us alive today.
> Delta is confirmed to be more contagious and less deadly.
Sort of, delta is confirmed to be less contagious and less deadly among a (significantly) vaccinated population. It is probably more contagious than the initial variant among an unvaccinated population, yes. But whether or not its more or less deadly, or whether vaccines + improved treatments have reduced the severity/survivability isn't clear. So delta is less deadly in practice at a population level, but it might be more deadly in only the unvaccinated population, or the same, or less. We don't really know.
I think I may be reading/interpreting your comment incorrectly after writing this/digging up these sources -
Whether or not Delta specifically is causing a larger impact on severity of outcomes, we know for a fact that it's more transmissible. And unvaxxed are quite literally dying 99:1 against vaxxed now - mostly from delta. Even if it's less likely to kill/cause severe irreversible organ damage per case, it seems somewhat safe to say the vast majority of unvaxxed are going to get it sooner than later at this point because of increased transmissibility - which will lead to a giant pile of bodies that didn't need to happen.
I would like to think that info alone probably indicates that delta is having a larger affect on the severity of outcomes, but I know there's more to statistical analysis than that. Anyways.
So the virus itself isn't less deadly, it is just that we are better prepared.
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