NATURE QUOTE OF THE DAY Monday 4th Oct 2021 (Unattributed) from Nature magazine:
“Droplets and surfaces are very convenient for people in power — all of the responsibility is on the individual. On the other hand, if you admit it is airborne, institutions, governments and companies have to do something.”
Units, droplets, and masks
Speed of correction in scientific reports is never more important than when the outcome is a change to medical practice. UK Government regulations for reducing the spread of COVID-19 suffered from prolonged repetition of faulty advice based on an incorrect assumption about mode of transmission. Accepted guidance was that respiratory infections were spread in “droplets” from a cough, sneeze, or voice of a symptomatic patient. Droplets would contain active virus and fall out of the air onto surfaces, often within a couple of metres, and would range in size from 5 -100 micrometres across (1000 micrometres = 1 millimetre). It was assumed that 2 metres distancing could minimise transmission through air even indoors, because these droplets would fall rapidly. So attention switched to surfaces. Studies found intact virus remaining on surfaces for days where they had dropped or been smeared. Hand washing and scrupulous cleaning of surfaces were therefore emphasised more than wearing face masks, let alone ventilation.
Unlike “droplets”, tiny aerosol particles, defined as less than 5 micrometres across, are buoyant, borne up by the slightest air current, staying aloft even in still air, and wafting far from their origin. But aerosols were not being blamed. Aerosols were not understood.
Accepted guidelines were following research dating back to the 1930s, pre-dating the technology for studying aerosols. This research had been quoted down the decades, incriminating the 5-100 micrometre “droplets”, plus the surfaces they rapidly settled onto, and aerosols were not considered. It took an environmental engineer, Linsey Marr, to recognise that the 5 micrometre minimum for dangerous “droplets” was wrong, and that anyway aerosol-type persistence was in fact possible for larger particles. She also set up demonstrations that air could contain persistent infectious aerosol particles that were even less than a single micrometre across, and that those were actually the main route of COVID-19 infection.
Fixation on that one misleading outdated measurement, “5 micrometre minimum”, had delayed acceptance that COVID-19 mostly spreads through the air and rarely through contaminated surfaces. Old textbooks had been read, used, but not checked, so months of public health guidance served mainly to reduce hand transmitted food poisoning and promote furniture polishing. It was scant defence against the airborne COVID-19.
Proofreading Large and Small
A Cautionary Tale: Small errors are easily overlooked when the reader is apt to see their expectation rather than the text.
But an arguably gigantic error was overlooked in 1631 when the “Wicked Bible” was published with the 7th Commandment in the Book of Exodus reading “Thou shalt commit adultery” . Who can say whether this was an egregiously clunky failure of proofreading, or an instance of mischief ?
DNA proofreading : Small
Accuracy is never more vital than in the replication of DNA during cell division, so that both daughter cells get a correct copy, and growth plus reproduction can proceed. With just four “letters “ the DNA code forms sequences like words, words that embody instructions to each body cell as to what to do to stay alive and healthy. Even the smallest error (ie. mutation) can occasionally be disastrous, as when human DNA has just one wrong “letter” among thousands in its instruction for making the red Haemoglobin in blood: result – sickle cell disease.
In total there will be billions of “letters” per cell, and a few random errors don’t normally matter, but like other animals, humans have proofreading systems in their cells to maintain incredible DNA accuracy. Not quite 100%, or nothing would change, so there’d be no evolution. We’d still be what we hope to find on Mars – very small, simple: slime.
Virus proofreading : Smaller
Viruses are much simpler than cells but it’s still in a virus’ interest to copy DNA accurately so as to infect a host and carry on its life cycle. Influenza is a simple little creature even as viruses go, and every year it comes back slightly different, as it has no means of detecting and correcting DNA errors. There will always be a few new mutations, which necessitate a yearly ‘jab’ for the new strain.
Coronaviruses are bigger and more complex than flu, and so sophisticated as to have a “proofreading” system for quality control. Thus it was said in 2020 that Coronaviruses were stable and one vaccine would solve the problem. The UK’s superb sequencing capacity was even under-used before Christmas 2020, as it was believed that COVID-19 would remain unchanged. Mutations would be extremely rare, and be detected then corrected back to the original type. No point in sequencing sample after sample and never finding variants.
But billions of vulnerable people worldwide and billions of viruses per patient mean an awful lot of viruses – a lot of chances for just one extremely rare random mutation to bypass the proofreading, survive, and then turn out to increase infectivity. The Delta variant of COVID-19 is a stark example of this evolution.
Quantum “proofreading” : sub-microscopically small
Any virus is a colossus beside the sub-atomic particles running quantum computers. Quantum computing is super-fast, calculating in minutes what would take our classical computers over a million times longer.
Except, they are so error-prone that a paper in the journal Science, October 2021, hailed as a major advance: “For the first time, a quantum computer has demonstrated an error-correction strategy that fixes more errors than it creates”. Quantum computers have an error rate of about one operation in 1000, but for practical use that needs to be way below 1 in a million. The correction process is unlike anything in classical computing – and anything in the ordinary world – but it seems that the practical limit on the quantum computer’s near-miraculous speed is its “proofreading.“
Two Cautionary Tales: Check the units!
In 1999 NASA’s Mars Climate Orbiter craft after spending 10 months travelling to Mars approached too close, broke up and burned in the Martian atmosphere, due to a mismatch of measures. Attempts to introduce metric units throughout the USA had failed, and the craft’s designers and builders still used old Imperial measures. The Jet Propulsion Laboratory were accustomed to the necessary conversion and assumed it had been made, which in this expensive instance, it hadn’t. The failure to check was admitted by NASA in October 1999, and cost $125 million.
I must end on a humbler personal note: a hutch for guinea pigs ordered online assuming its measurements to be in centimetres, will not fit into a tiny flat if the measurements are in inches.