> Is there any theory or data that more the R or transmission rate less deadly the virus is in itself?

There's a vague evolutionary argument that the less deadly for the host a parasite is the more widely it can spread and thus the more evolutionarily successful it will become. But there is no mechanism that guarantees the inverse — that an increase in infectiousness will be accompanied by a decrease in lethality. From the molecular biological perspective, the molecules responsible for viral spread and the molecules responsible for the damage that the virus does to its host (or that the host does to itself when attacking the virus) are likely to be quite different, so there is no reason for a change in one to be accompanied by a change in the other.

> But there is no mechanism that guarantees the inverse — that improvements in infectiousness will be accompanied by a decrease in lethality.

I’m not clear; the argument effectively defines infectiousness as how-not-lethal the virus is. Thus, the virus cannot be made more infectious without decreasing lethality.

There is however an interim period, as evolutionary arguments are long-term arguments, where the virus can be both more infectious and more deadly, before settling into its stationary state.

The molecular perspective isn’t too useful against an evolutionary argument as well — evolution is always a sum-of-the-parts system. The question is simply: is the virus ultimately more capable of spreading? And at least in the extreme, an instantly killed host is unlikely to do an real spreading, no matter how trivially the virus could spread (had the host persisted). And in the other extreme, a completely non-lethal virus can survive and spread forever, especially in dense populations, especially if it doesn’t incapacitate the host significantly (acting as a simple parasite), allowing it to continue meeting new hosts.

Of course, a virus that doesn’t need the victim to be the host is a different story; eg malaria persists and spreads through mosquitos, so it could instantly kill humans and yet receive no evolutionary pressure against it.

One of the things that has made this particular virus so successful is that it does the larger part of its spreading before there are any major symptoms. In this case, the only thing about lethality that will reduce infection rate is the degree to which it makes everyone more careful (or makes more people at all careful).

I've read that the viral load is 10-20% higher on average, so if anything it's the opposite, but so far no one has gone on record saying it's more severe. It's more the compounding effects of higher viral load and easier transmission. Unfortunately, the UK hospital situation will probably get worse based on those two assumptions.

Viral load is a poor metric. It is higher before major symptoms start (before it moves from UR to lungs), and so it goes down over time. You can be dying of COVID and test negative altogether if you’re fully past the initial stages (though you won’t be contagious, which is arguably the real point of the test). So a) a newer variant will definitely have a higher viral load on average just because people are more likely to be at an earlier stage in the infection cycle, especially if it is more transmissible, b) if a virus theoretically stays in the upper respiratory for the duration of the infection, it’ll have a higher average viral load while being less dangerous (in that sense, they are inversely correlated).

> So a) a newer variant will definitely have a higher viral load on average just because people are more likely to be at an earlier stage in the infection cycle, especially if it is more transmissible

Why would that be? The new variant is several months old already. See e.g. Figure 1A in the report [1]

[1] https://www.imperial.ac.uk/mrc-global-infectious-disease-ana...

The increase in viral load is a bit more substantial than 10%... The study [0] shows a 10-100x increase for the median case.

[0] https://www.medrxiv.org/content/10.1101/2020.12.24.20248834v...

Yeah you're right, I'm a week out of date. That is disturbing. Perhaps that means it is actually higher viral load but lower impact per amount of virus?

The herd immunity thing is still a pipe dream. No one has mentioned or even hinted at it being less lethal so I'm not sure why that would even enter the discussion.

Yeah, the only way we're getting to herd immunity without the current disaster becoming exponentially worse is with the vaccines.

No, not really. The letality of the new variant seems to be the same but of course, more infections will mean more causalities

It is already bearing chaos in British hospitals, and it’s early days.

With 50k infections a day, say the true number is 100k, in 3 months only about 1.5% of the UK popularion get infected, not really significant for her immunity numbers.

Is that right? 100K daily infections give you 100,000 x 30 x 3 = 9,000,000 in three months which is 13% of 68M. Not anywhere close to herd immunity but not 1.5% either

Based on an IFR of 0.44, around 17 million already have contracted Covid. 9 million will not get us to full herd immunity, however, will reduce super spreading events (as super spreaders will already have had the disease)

Ah yes my bad, off by 10x . Make it 15%. More, though as you say, not “enough more”

Vaccinations can bring us closer to herd immunity too. Or at least take the load of the hospital system by covering off the vulnerable population.

You're off by an order of magnitude.

Well, it’s a week after x-mass so all countries see big increases because of family gatherings

Mortality is said to reduce because less severe virus keep the hosts more mobile and increase chances of transmission, outnumbering more severe variants.

For the COVID though, IIUC there’s 4-day asymptomatic phase where most of transmission occurs, followed by 2-week symptomatic phase, and it is thought to be unique. So it’s not clear if normal rules of thumbs apply to it.

I don't think that herd immunity can be achieved without a vaccine. We never had herd immunity to smallpox, polio, measles, mumps, rubella, varicella, or any other virus until we had vaccines for those viral diseases.