Matt Cavanaugh wrote: ↑
FTR, out of a population of 100,000, we've had 36 confirmed cases so far, and a single death -- and that was a snowbird who'd recently traveled abroad and had preexisting health issues.
Sounds like a prime population for a new virus seeking to make friends and maybe more...
The general public's understanding of epidemiology depresseth me. What do we have to work with? Diagnosis. Contact tracing. Quarantine.
Diagnosis: we have a decent test. Gets it wrong a fair bit, but given that the experience in Iceland is showing half the people with a positive result didn't even have any symptoms, we cannot rely on testing to identify infectious people. And for ex post facto diagnosis, we have an antibody test, but whilst it might be used to allow people out of quarantine, it won't reduce deaths.
Contact tracing: a labour intensive effort to identify people who may have been infected and quarantine them so they may not infect others. Useful if infectious people are easily identified. Not useful if asymptomatic people are infecting others.
Quarantine: an excessive concept in etymology, as 40 days are not needed. Useful if someone might be infectious and should be isolated until they are dead or recovered. Very limited value if asymptomatic people are infecting others.
There was a brief window, now past, where an alert and primed society might have tested anyone with 'flu-like symptoms and isolated them, traced their contacts, and then isolated them in turn. That's good old-fashioned public health at work and that's what Taiwan did (maybe because of a traditional distrust of anything from the mainland). 428 cases, 6 deaths as of today. Pretty good for a population of 23.4 million. We failed to learn from their experience, as the WHO was influenced by (The Peoples' Republic of) China, and did not tell us.
Now, given that the very brief window for testing everyone with 'flu-like symptoms is long gone, and the fact that many with the novel coronavirus have no symptoms, there is no prospect of testing and individual isolation, never mind contact tracing and isolation of contacts, Taiwan's approach is no longer applicable. I should add here that one very important factor in the genesis of any epidemic is whether a disease may be passed from person to person. If you had to eat poorly cooked bat soup this disease would be harder to catch than if simply being in the same room as an infected person would do the job. Once again, the WHO took China's word that it was not a virus capable of person to person transmission. In retrospect one wonders if anyone at the WHO was sober; if they had known anything of the numbers affected in Wuhan they would have guessed. An epsilon semi-moron would have guessed correctly. But they chose to go along with China's press releases. It looks like each infected individual infects around five other people. That's a massive problem, as it will overwhelm contact tracing unless undertaken with total diligence when cases are in single digits. There's another massive problem to come from that infectivity rate, but let's depress you later with that. So, if you have high infectivity, and 50% asymptomatic but infectious individuals, you are screwed. Isolation for all is the only remaining tool left in the BatBelt.
So that's what most countries have done, and as it works, those whose bank accounts are suffering are beginning to make much noise about it. Understandable. How should a total lockdown work? Well, it means the number of deaths will be reduced because of reduced opportunities for transmission. It should put the brakes on new cases, and it is to be expected that people locked down will look around and wonder what the fuss is about. But viruses survive, They don't disappear. Look how quickly we have seen measles chickenpox, polio and mumps surge back as soon as vaccination rates fall below certain thresholds. Stop the lockdown and watch the deaths begin again. This is a certainty, not a speculation. Either over a long slow and painful period, we will lockdown, relax, lock down again and so on and so forth, get to a point where herd immunity prevents general transmission, or we could fail to do anything at all, and get to herd immunity with greater numbers of deaths and total chaos in out hospitals along the way (which also means dramatically higher death rates from other, non-Covid-19, causes when patients with everyday diseases are denied care).
Now let us
pray consider herd immunity. There is a non-linear correlation with infectivity. If a sufferer infects one other person on average before dying or recovering, then herd immunity is achieved when 50-60% of the population is immune. But if a sufferer can infect 5-6 other people, we would need 80-90% immunity before disease transmission among the remaining susceptible population is unlikely. Note that we need much more of the population to have been infected and recovered (or died: for these considerations it matters not), and that there are a lot fewer people left to protect - maybe 10-20% - with this herd immunity. Before public health measures and epidemiology were around, a disease like this would have infected 80% of the population, killed the other 20%, and history would have wandered onwards with few academic historians studying the tiny hiccup in birth and death statistics. So is there anything at all we can do to influence the development of herd immunity? Oh, yes. Quite a bit. We could go for the variolation approach, or the vaccination approach. Variola is smallpox. Time was when a healthy person would be inoculated with the lymph from a smallpox vesicle. They would either live, or die, but if they lived they would be immune. When Edward Jenner realised there was cross-immunity between cowpox and smallpox, he started inoculating people with vaccinia, or cowpox. Cowpox is a mild disease, and after the
vaccination, people had immunity to smallpox without having had the disease. So we could infect volunteers with Covid-19 (seriously
suggested by some), or we could make a vaccine (get the etymology now?). The remaining fly in that pot of ointment is this: some viruses do not stimulate lasting immunity. It might be that they mutate frequently (influenza), and it might be that they occur in multiple forms (there are around 80 known rhinoviruses that cause a "cold" and then even more adenoviruses that cause "summer colds"). And then, worryingly, there are stable viruses to which we make no lasting antibody defense (norovirus or Norwalk virus if you like - you get it, maybe are immune for next winter, but then you can get it again). A small percentage of South Koreans have been testing positive again for the novel coronavirus after seeming to have recovered. It might be that they meet it again, but do not get sick. It might be that our PCR test is only detecting the DNA of dead viruses and the subject's immunity remains in effect. But it may just be that we make no lasting immunity, which would probably imply no lasting benefit from a vaccine. Then, like bats, we become a species constantly infected and either surviving or dying, with our numbers being depleted by an ongoing battle between the virus and our immune systems.
Economic considerations aside, we can easily survive this virus in any scenario except the one where there is no lasting immunity. My guess would be that we survive that too, but in considerably smaller populations and as a much weaker society. And bringing economics into it, which I am not qualified to do (and I guess, no one else is either, since economics is voodoo rather than science), there are consequences from locking down (once, twice, repeatedly), or not locking down at all, accepting higher death rates but less disruption to economic life. No one, really, no one at all, knows what the consequences might be from these choices. It has never been done before, and we have only guesswork to go on. A rather cheerful thought, when the US news keeps telling us daily we must end the lockdown, or we must continue it. We don't know which course reduces deaths, which reduces economic losses, and what the best compromise might be. I can only say that anyone who claims to have the answer is talking through his ass. Whatever we do, most of us will survive, so don't go and shoot yourselves just yet.
My dog in this fight is a peculiar one.
► Show Spoiler
White blood cells come in two main types: neutrophils that kill bacteria, and lymphocytes that kill viruses. Lymphocytes divide into B and T subtypes. B cells make antibodies. T cells are hit men that kill any cell marked for death by B cells. My B cells are mostly useless, as they are a malignant clone that is growing without regard for my body's needs. And now I take a drug that kills lymphocytes, all of them. T and B. Good and bad, benign and malignant. So I can't fight any viruses, nor make any new antibodies to ever-so-politely-presented antigens in vaccines. It might just be that my poor immunity would let me meet Covid-19 and get by; I don't have the means to mount a cytokine storm, but on the other hand, I don't have the means to fight the infection in the usual way. Best not to meet it. Shall I wait for a vaccine? Given that we know well-established vaccines result in no new antibodies in people on my drug, because it kills the benign, white-hatted B lymphocytes who would have bid upon that contract, as well as the useless and malignant black-hatted ones, there's no reason to feel a vaccine would give me any benefit. The only answer is to acquire someone else's immune system, and let it kill all the remnants of my malignant one (whilst, please, sparing all the rest of the cells in my body that are foreign to it but rather useful to me!), and then hopefully acquire immunity to brand new things like Covid-19. Next week is time for my monthly phonecall to find out if a donor with the right degree (imperfect, just so as to kill the malignant cells but let the rest of me live) of a match has been found. I suspect most of us in this situation die of being tired of it before a match pops up. If not, the marrow-ablating chemo and radiation might do it, then the infections that arise as we wait for the transplant to sprout and grow, and then even the transplanted marrow might do it with graft vs. host disease. Bugger it all. I'm tired, but I'm not done yet.