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Archive for the ‘epidemics’ Category

the rapid testing system that went begging

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this is a screen shot taken from the video – the Ct values are inversely proportional to the viral load, and are plotted on a logarithmic scale (not drawn to scale though!). the x-axis is the infection time scale. viral particles can remain in the host for some time

For something completely different, I want to return to the matter of this pandemic, which in the past 24 hours has claimed more reported deaths in the USA since it began – a disaster of mismanagement, neglect, and of course the selfish civil disregard so typical of that country. 
But of course that’s a generalisation, there are plenty of productive, socially concerned, often frustrated individuals trying to buck the trend, and Dr Michael Mina is one of them. He’s been advocating for a type of cheap, home-based, fast turnaround test for this virus (actually for the proteins that the virus produces via the host’s own ribosomes) which would vastly reduce spread, eliminate the need for contact tracing, and help the economy. Had this type of monoclonal antibody testing been scaled up at the outset, and made available worldwide, it’s likely that countless lives would have been saved. And it may well be generalised for other outbreaks. 

So I’m writing this based on a video I watched, called ‘Rapid Coronavirus Testing – At HOME (COVID-19 Antigen Tests) with Dr. Michael Mina’. The video was produced in late July, and of course no progress has been made, and in the US the case numbers and the death numbers have jumped to the highest so far recorded, and rising. 

So Dr Mina is a well-qualified immunologist whose impressive bio is detailed in the video. His ideas on this topic are published in a paper entitled ‘Test sensitivity is secondary to frequency and turnaround time for Covid-19 surveillance’, which has eight co-authors. The title captures the whole argument really, but I want to clarify to myself and others these issues of sensitivity and frequency. The video begins with a point-by-point comparison of the ‘paper antigen testing’ Dr Mina advocates, and RT-PCR (reverse transcriptase – polymerised chain reaction) tests, which are currently considered the gold standard. Firstly, the antigen tests are potentially much cheaper, once scaled up, and can be made for $1 to $2 per test. The PCR tests currently cost between $35 and $100 each. Secondly, the result of the antigen test can be known in 15 minutes, while the PCR test takes a minimum of 3 days, sometimes 7 days or longer. Third, the antigen test can be self-administered at home, while the PCR cannot. Fourth, the antigen test can be used daily, or three times a week, or with as much regularity as can be wished for or afforded, whereas this isn’t really viable for the expensive PCR test. Fifth, the simple antigen test can easily be mass-produced, but the lab processing involved in the PCR test would make this difficult. The sixth comparison favours PCR, which has a high sensitivity at over 90%, meaning that if there’s any virus present, it is over 90% likely to detect it, whereas the antigen test has a likelihood of around 55%. However, the antigen test will be able to pick up the majority of infectious cases, which is the key requirement. This will be explained later. 

As Dr Mina points out, the rapid antigen test is a public health measure, unlike vaccines and therapeutics, which are medical interventions. The vital point he is making is that much investment is being put into the medical interventions, which, if successful, will bring solid returns on those investments. And so that is why so many private firms are competing for producing these ‘quick’ and hopefully effective, fixes, whereas there’s no return on investment for a public health measure such as a rapid, effective testing regime, even though this would be the best thing for keeping an economy running during a pandemic. It would require effective, good faith governance – something in short supply, particularly in the US. 

So there’s a lack of financial incentive to scale up this rapid testing system, and according to Dr Mina, there’s also a regulatory problem. There’s no technical problem to scaling up, but as Mina says, there is a grey zone for this kind of testing which means it doesn’t quite fall under FDA’s guidelines, and there seems to be no governmental will (given that the USA currently has no federal government, and hasn’t really had one for four years) to provide a regulatory pathway for this kind of unique public health tool. FDA or other authorised approval is essential for mass-manufacture, and this isn’t forthcoming. As Mina says, this isn’t a diagnostic test, and isn’t meant to compete as a diagnostic test, it’s meant as a public health measure to prevent spread. So it’s a human and political problem, and this period in the USA is obviously bad for that sort of thing.  

So the regulators appear obsessed with high-sensitivity testing, which tends to be expensive. If PCR testing could be done cheaply, at home, with rapid turnaround, that would be ideal, bit it isn’t going to happen, for a variety of reasons. This sensitivity issue needs to be looked at more closely, in the context of a rapidly multiplying virus, within a particular host. The rapid antigen tests may be a thousand times less sensitive than PCR, which sounds useless but not if you understand the virus and its action. It starts with a tiny number of parts per millilitre, and when it gets to a larger number, the PCR test will pick it up, and then when it gets much larger still, the androgen test will pick it up. But even then, the viral load will not be enough to effect transmission (and this will vary between individuals). And the whole aim is to prevent transmission, rather than the virus itself. The antigen test will tell you that you are transmitting (more later), and is effective in stopping or breaking that transmission chain. Testing frequency becomes more important than sensitivity. PCR tests conducted weeks apart could miss a whole infection cycle.   

The FDA at the time had a news release entitled ‘FDA posts new template for at-home and over-the-counter diagnostic tests for use in non-lab settings, such as homes, offices and schools’, which sounds like just what the doctor ordered, but Mina points out that, though the regulators are showing willingness to relinquish testing power to members of the public to some degree, they’re clearly not willing to swap what is in essence a lab-based, PCR-type test, with all its super-sensitivity, for a rapid antigen test. So, no real possibility of rapid turnaround, and they require reporting of all positive and negative tests to the relevant lab or the Department of Health, rather than at-home monitoring. Among other things that means more work and more expenses for the monitoring company. Most results would obviously be negative, so a great deal of logistics to cover every negative result, which people probably wouldn’t comply in reporting anyway. So, not very viable. Dr Mina compared it to cheap instant coffee compared to those super-expensive Nespresso coffee machines that presumably the elites buy. The instant coffee version does the job without the bells and whistles, and he believes it’s the best intervention possible, short of a vaccine.

And that was in July, and the current death rate and case rate are breaking all records, but of course a vaccine is round the corner – maybe. So the moment has probably gone, but the lessons still need to be learned, by a more responsible administration. I will keep on this topic for the next couple of posts.

Reference

Rapid Coronavirus Testing – At HOME (COVID-19 Antigen Tests) with Dr. Michael Mina (video)

 

Written by stewart henderson

December 5, 2020 at 10:06 pm

reading matters 11 – encephalitis lethargica. Will it return?

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Asleep, by Molly C Crosby, 2010

Canto: This was one of the saddest books I’ve read in a long time. It’s about a disease that arose, and was recognised, at around the time of the ‘Spanish flu’ of 1918, though it was more sporadic and long-lasting, and rather more mysterious. It’s also a kind of cautionary tale for those among us who downplay the impact of diseases and their effects, which are so often long-term and horrifically devastating. It’s humbling to realise that we just don’t know all the answers to the pathogens that strike us down. 

Jacinta: And could revisit us, in mutated and perhaps even more deadly form, some time in the future. This book is about encephalitis lethargica, a disease that was personal to the author, as it infected her grandmother, whose entire life, though she lived to a goodly age, was clearly stunted by it. She was struck down at the age of 16, and slept for 180 days, and though she lived almost 70 years afterwards, she was robbed by this brain-blasting illness of the life of the mind, the rising above ourselves and grasping of the world that we’re attempting in this blog. Through sheer bad luck. 

Canto: And as Crosby points out, her grandmother was far from being the worst-affected victim of this disease. People died of course, but others were disastrously transformed.

 Jacinta: So let’s go to a modern website, a department of the USA’s NIH, the National Institute of Neurological Disorders and Stroke, for a definition:

Encephalitis lethargica is a disease characterized by high fever, headache, double vision, delayed physical and mental response, and lethargy. In acute cases, patients may enter coma. Patients may also experience abnormal eye movements, upper body weakness, muscular pains, tremors, neck rigidity, and behavioral changes including psychosis. The cause of encephalitis lethargica is unknown. Between 1917 to 1928, an epidemic of encephalitis lethargica spread throughout the world, but no recurrence of the epidemic has since been reported. Postencephalitic Parkinson’s disease may develop after a bout of encephalitis-sometimes as long as a year after the illness.

Canto: Yes, and having read Crosby’s book and knowing about the worst symptoms and a few heart-rending cases, the sentence that most strikes me here is, ‘The cause.. is unknown’. Apparently Oliver Sacks’ book Awakenings, which we haven’t read, is all about patients who have ‘awakened’, permanently damaged, from this bizarre disease, and that’s a book we now must read, though of course it will provide us with no solutions.   

Jacinta: And no arms against its future devastation, should it return – and why wouldn’t it? Crosby and others have suggested that ‘fairy stories’ like Sleeping Beauty and Rip van Winkle may have been inspired by outbreaks of the disease. Of course this is conjecture, and only if the disease returns will we be able to attack it with the technology we’ve developed in the intervening century. As the neurologist Robert Sapolsky points out in his mammoth book Behave, (so mammoth that I can’t find the quote), the number of papers published on the brain, its activity and functions, in the 21st century, has grown exponentially. We might just be ready to counteract the long term horrors of encephalitis lethargica next time round, if it comes around. 

Canto: Crosby’s book is organised into case histories, featuring people who fell into this bizarre torpid state for long periods, and when aroused, often behaved in anti-social and self-destructive ways that in no way resembled depression, between bouts of a ‘normality’ that was never quite normal. And one of the saddest features of these case histories, richly described in the notes of famous figures in early neuropsychology, such as Constantin von Economo, Smith Ely Jellife and Frederick Tilney, is that the victims disappeared into the void  once it became clear that no known treatment could save them.

Jacinta: Yes, some may have died soon afterward, others may have lived on in a limbo, locked-in state for decades. In fact the symptoms of this disease were bewilderingly varied -various tics, hiccupping, catatonia, salivation, schizoid episodes… Encephalitis literally means swelling of the brain, and it doesn’t take a medical degree to realise this could cause a variety of effects depending on which area of the most complex organism known to humanity is most affected. 

Canto: Encephalitis is usually caused by viruses, and of course viruses hadn’t been fully conceptualised when von Economo wrote his 1917 paper on what was to become known as encephalitis lethargica, as the role of DNA and RNA was unknown. However, von Economo was the first to recognise the vital role of a tiny, almond-shaped section near the base of the brain, the hypothalamus, in the distorted sleep patterns of these patients. He also wondered if there was a connection between the so-called Spanish flu and this sleeping sickness.

Jacinta: Yes, and this brings to mind the current nightmare pandemic. People, including of course epidemiologists, are wondering about the long-term effects of this virus, especially in those who seem to have recovered from a serious infection. Crosby writes of the situation a hundred years ago:

The war had provided the first opportunity encephalitis lethargica had to crawl across the world with little notice from the medical community. And by 1918, the pandemic flu had given it the second opportunity, stealing worldwide attention, infecting and killing millions. Epidemic encephalitis moved with the flu, almost like a parasite to a host, often attacking many of the same victims, receiving very little notice at all. 

Of course there has been no sign of a return of encephalitis lethargica – as yet – from a medical community that is somewhat forewarned, but it’s clear that inflammation can have very diverse effects, especially when it involves the brain. 

Canto:  But it’s like an undefeated enemy that has gone into hiding. We’ve defeated smallpox; tuberculosis and polio are in heavy retreat; leprosy seems as remote to us as the Bible, but this sleeping sickness, some of the victims of which have died within our lifetimes, has tantalised us with its bizarre and devastating effects, but has never really given us a chance to fight it.

Jacinta: Yes fighting is what it’s all about. The anti-vaxxers and the natural health crowd seem to want to leave everything to our immune system, to let diseases take their course, killing and maiming a substantial percentage of the herd to let the remainder grow stronger. If they were to read some of these case studies, to witness the lives of young Rosie, Adam and Ruth, they would surely think differently, if they had a modicum of humanity. 

Written by stewart henderson

September 18, 2020 at 11:01 pm

Reading matters 8

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Outbreaks and epidemics, by Meera Senthilingam, journalist, editor and public health researcher, specialising in global health and infectious disease.

  • content hints – Dr Liu Jianlun, index case, ancient viruses, smallpox, ancient Egypt, eradication v elimination, hookworm, yaws, polio types 1,2 and 3, malaria, measles, Guinea worm, Edward Jenner, cowpox, eradication programme 1967, WHO, Donald Henderson, SARS, Zika and microcephaly, Ebola, mosquitoes, MERS-CoV, Crimean-Congo Haemorrhagic fever, Rift Valley fever, Yellow fever, more mosquitoes, breeding grounds, Aedes aegypti, Lassa fever, tuberculosis, syphilis, gonorrhoea, chlamydia, MSF, International Red Cross, dengue fever, staphylococcus aureus, bacterial meningitis, rabies, zoonoses, vectors, vaccine hesitancy, seasonal influenza, types A (H1N1), B, C and D, asymptomatic spread, antibiotic resistance, failed infrastructure, effects on poverty, affected by poverty, Dr Jan Semenza, effects of globalisation, investment, learning, co-operation…

Written by stewart henderson

August 9, 2020 at 11:45 pm