Thoughts on Mortality

I was updating my Covid-19 statistics page yesterday after the daily announcement and I noticed that it has now been ten consecutive days since the last Covid-19 related death in Ireland. As of yesterday there were only 40 people with Covid-19 in hospitals in the Republic, six of whom were in intensive care.

These low numbers are of course very good news indeed, but it got me wondering why. As you can see from the above graph, new cases started to increase about two months ago. In the first wave the mortality figures started to grow with a much shorter lag, although it is difficult to be too precise about it because of delays in testing and reporting that shifted the blue curve to the right.

With new cases in the Republic now appearing at an average rate of around 100 per day and assuming a mortality rate of a few percent, one might have expected to see the mortality figures rising, but this has not happened. It must be said though that the current level of new cases is much lower than the initial peak, as this linear plot (also smoothed on a 7-day window) makes clear:

An even more remarkable case is that of France (data from here):

The blue curve is a 7-day moving average. You can see that the level of new cases in France is about the same as it was in late March. The daily mortality figure however looks like this:

So the mortality rate among recent cases is much lower in France than in Ireland.

I’m not going to discuss mortality data in the United Kingdom as these are being fiddled by the Government who have arbitrarily decided not to count anyone who dies more than 4 weeks after testing positive for Covid-19 in the figures. It’s a blatant con intended to make people think that the situation in the UK is better than it actually is.

I suppose the main factor for this is that the more recent cases are not happening in hospitals or care homes and they are affecting mainly younger people who have no underlying health conditions; over 70% of the recent cases in Ireland are people under the age of 45. It may also be that the treatment of patients is more effective now that it was in March and April.

Some people are arguing on social media are saying that data such as these prove that the Coronavirus has lost its potency and is no longer a threat. In order to provide evidence in support of such a claim one would have to take account of the differences in demographic and health history of new cases versus older ones, and I have not seen such a study.

Update: I had a terrible feeling that this would happen, but the same day I wrote this a further Covid-19 related death was reported. This was however a late notification of a death that occurred in June. For the latest figures see here.

29 Responses to “Thoughts on Mortality”

  1. John Peacock Says:

    I’m sure you’re right that this is mainly about young people partying away and being much less likely to die than the care home residents who were packing the statistics back in April. As to whether it’s a threat to these youngsters, I believe your chances of dying from the virus if you get infected at age 30 are about 1 in 500. That seems disturbingly high to me, and I think I would have the same view if I was still 30. And you can multiply that risk by several for all those that avoid death but are left with long-term health impacts. Is a 1 in 100 risk of serious consequences enough to worry about? Well, 99% of the time you’ll be fine, so put that way it sounds so much better. Once our undergraduates come back next week, I fear Edinburgh will be full of 99%-panglossians.

    • Here in Ireland the majority of recent cases have not been young people at house parties, but people working in meat processing plants and living in direct provision centres. That may well change when the students go back to college though. Young people seem to behave in many ways as if there are immortal…

      • Phillip Helbig Says:

        We are only immortal for a limited time.

      • Anton Garrett Says:

        Why do you think that armies recruit young?

      • nannacecilie Says:

        The attention has been on the meat plants and they were the cause of the big spike a few weeks ago and the Kildare lockdown. The main source of transmission now is social gatherings in private houses. There has not been as much attention in this, probably in part because it is not politically convenient. For example we were never told of the 50th birthday party in Donegal that led to a cluster of over 20 cases, and that was before the meat plant outbreaks.

      • I have never heard of that Donegal story. Do you have a link?

      • nannacecilie Says:

        I know of this (indirectly) from a public health worker in Donegal. No such information is forthcoming from official sources. I find that they are very secretive here compared to other countries.

  2. Hate to say this but the change to stats in England was sensible. The government’s original figures included all deaths after testing positive no matter what the cause of death or gap between testing and death. The 28 day figure now matches reporting in Scotland and Wales. The ONS death figures are most reliable as they look at death certificates that mention COVID but are two weeks behind.

    • telescoper Says:

      Matching Scotland & Wales does not of itself make it sensible…

    • Phillip Helbig Says:

      One shouldn’t replace one bad strategy with another. If someone tests positive but then dies in a car crash, they shouldn’t be counted as a COVID death. But someone who tests positive and dies 60 days later of COVID-related symptoms? Sure.

      This is a general problem. A football player who dies of a heart attack while playing dies of a heart attack. A diver who dies of a heart attack while diving died in a diving accident.

  3. I don’t know about Ireland, but in many countries testing is now much more extensive than in April. It may well be that the number of cases (in particular mild ones) in April was badly underestimated, so the mortality rate looks much too high.

    • telescoper Says:

      To take the example of France, there have been 286,007 official Covid-19 cases and 30,661 deaths. That’s a mortality rate of over 10%. In Ireland it’s 29025 cases and 1777 deaths, which is about 6%.

      The UK figures are 337,168 cases and an “official” death count of 41,504 (although the actual figure is probably over 60,000), which is an official 12.3%.

      How much of these differences are due to testing strategy I don’t know.

      • Phillip Helbig Says:

        One needs to look at the mortality rate in a group of people all of whom have been tested.

      • nannacecilie Says:

        The best estimates for the infection fatality rate is somewhere around 0.6% but it varies hugely with age. The far higher case fatality rates in western Europe (and Canada) is partly due to the lack of testing in the initial phase (and continued lack of testing in France, Netherlands and Sweden), partly due to the age profile of the populations, and partly the bad mismanagement by governments across the western world, in particular in relation to nursing homes. No other part of the world has as high case fatality rates as here (the sole exception being Mexico where the testing levels are abysmal with a test positivity rate of almost 50%).. This tends to be lost in the public debate because surely it is not possible that western Europe can be worst in the world in protecting its citizens?

        In arab countries which have had a huge caseload (but also very high testing levels) the case fatality rate is around 0.5%, presumably largely due to their young populations. In Qatar, with the highest infection level in the world, it is less than 0.2%. The standout case is Singapore, with almost 57,000 cases but only 27 deaths – almost certainly because they have managed to confine the outbreak entirely to the migrant worker population, which is presumably a young age group. The same may be the case in Qatar.

  4. Anton Garrett Says:

    Has the virus itself weakened? SARS-CoV-1 went away without any obvious natural selection-related reason. Good news if so.

    • nannacecilie Says:

      There is no evidence of that. Sars-Cov-1 was eradicated in part because of infection control measures and in part because it was too deadly and not sufficiently infectious. It also did not have asymptomatic transmission. Sars-Cov-2 is less deadly and more infectious and hence harder to control.

    • The peak infectiousness for SARS-CoV-1 was after the onset of symptoms, so when these people became a problem, they were already in a hospital ward and removed from the streets.

      Unfortunately, SARS-CoV-2 inferred peak infectiousness is about 2-3 days before symptom onset (if they do develop symptoms).

  5. A few possible reasons that are being investigated for the the lack of hospital cases.

    At the beginning on Pillar 1 tests were being conducted (hospitals); Pillar 2 (community) is now the dominant one.

    In the UK the mean age of those testing positive before August was 54, in August it was ~39.

    There’s a relationship between viral load (how much you take in from infectious people), and severity of symptoms. There appears to be a positive correlation. Also, masks seem to play a greater impact than realised. Not only as a source-control for the infectious, but also as a filter for the healthy, bringing down the viral load. Also an observed trend of increased mask wearing and increase proportion of asymptomatic people.

    With regards to food processing sites: they’re likely to be noisier environments, so people are talking loudly. The louder the volume, the greater the number of aerosols that are produced and thrown in the air. (Examples of outbreaks at choirs, religious services, karaoke.) Also, colder, drier, environments are problematic. Heavier droplets containing the virus that would otherwise fall to the floor due to gravity can become aerosolised as they dry in the air, thus staying suspended in the air.

    People have been out in the good weather, of which there are plenty of air currents to dilute infectious aerosols and UV-light for virus inactivation.

    Not a personal plug, but created this quick summary website:

    The biggest takeaway is that outbreaks overwhelmingly happen indoors compared with outdoors. It’s a ventilation problem.

    • Anton Garrett Says:

      How can it be the case that there is a correlation between how much of it you take in from the people you catch it from, and the severity of your symptoms? Given that it multiplies inside you, I would expect the former variable to influence only the length of time before you show symptoms, not their severity.

      • I have wondered if there might be different strains of the virus, some of which are more virulent than others.

      • Phillip Helbig Says:

        Apparently viral load also plays a similar role with AIDS.

      • Anton Garrett Says:

        What do you mean by similar? We are discussing whether symptoms due to SARS-CoV-2 are more or less severe according to how much of it there is around when you catch it. With HIV I would expect this variable to influence your probability of catching it rather than its severity if you catch it.

      • Phillip Helbig Says:

        I’m not expert, but presumably the amount one is exposed to influences the probability of gettng infected whatever the disease. That seems so obvious that my guess is that people would be discussing viral load only if it had some other effect.

      • This paper is on mask wearing on reducing viral load, and references other papers discussing inoculum and symptom severity

        It appears that it’s down to the immune response. The immune system initially mounts a defence. For a small dose, the immune system quickly gets control. For larger doses, it has more of a battle.

        For those who are struggling against SARS-CoV-2, the immune system can set off a ‘cytokine storm’ – an all out attack on the virus, but also does damage to the body. In these people, their lungs get damaged, and they’re then susceptible to other pathogens which can cause pneumonia.

        Further, for those who have longer-term symptoms, it’s been proposed that the immune system is stuck in a loop. It doesn’t fully switch off, so people begin to feel better, then suffer fatigue and variable heart rate because the immune system’s reactivated etc.

        With regards to the virus itself, some minor mutations have happened, but it’s not thought it significantly changes how it affects people. More of a small tweak for chemical stability?

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