Sunday, 29 March 2020

COVID19 – Once Again On Testing

The government is again making a big thing about testing for COVID19. Tony Blair also chipped in, saying that probably everyone would have to be tested. The government is lining up numerous places to produce testing kits, which will not become big business for something only months ago, nobody knew we needed. But, there are two types of test, and, at this stage of development of the epidemic, only one type of test makes any sense in undertaking. That is the test to see who has had COVID19, and, thereby, acquired immunity to it. That is not what most tests being undertaken are seeking to ascertain. 

South Korea has been very successful in constraining the spread of COVID19, and deaths from it. It has done so without any lock-down of its economy, of the kind that was implemented in Wuhan, in Italy, the UK, and elsewhere. It achieved that for one simple reason. Right from the beginning, South Korea tested anyone coming into the country to see if they had COVID19. If they did, it isolated them until they were no longer infectious, thereby stopping the spread of the disease. As soon as anyone, already inside the country, showed symptoms, they too were tested. If they were shown to have the virus, they too were isolated, and everyone they had been in contact with was traced, and tested similarly. They could do this, because, doing it early, the absolute number of infections was manageable. In these early periods, the number of cases of infection was say, 100. We know that for every person infected, during the period they are contagious, of up to two weeks, they, on average, infect three more people. So, starting with 100 cases, in a fortnight, they would infect 300 other people. That 300 people would, in the next fortnight, infect 900 people, and so on. 

But, its relatively easy to be able to test 100 people, especially if most of these are people who are routinely tested on entering the country. Quickly testing this 100 people, and preventing them coming into contact with others, prevents them spreading the virus. Identifying those they came in contact with, quickly, and testing them, reduces the time they can be infecting others, if they had, in fact, been infected themselves. If 300 people are infected over 2 weeks, that is approximately 20 people per day. So, taking into consideration the initial 100 people, if 120 tests per day are conducted, the further spread of the virus can be checked. That is what South Korea managed to do. Even if the original number is 1,000, rather than 100, it means that so long as you test 1200 people per day, and effectively trace the consequent contacts, you can isolate all those infected, and thereby prevent the spread of the virus from the start. 

China had failed to do that, so that the number infected already ran into the tens of thousands. The same is true with Italy, and with the UK, and the US, Spain, France and elsewhere. Unless you do this extensive testing and tracing right at the start, when the numbers are manageable, testing to see who currently has the virus is pretty meaningless, and useless, taking up valuable time and resources, firefighting, when that time and resources could be better utilised elsewhere. The total number of people infected in the UK, for example, based upon the current number of deaths, and a mortality rate of 1 in 1000, is over 1 million. In fact, because it takes around three weeks for people to die, after they have been infected, the current number of deaths, at over 1,000, probably means that more like 3 million plus people have already been infected with COVID19, in Britain. But, if we start with the 1 million figure, it becomes obvious why it is impossible to test on a sufficient scale, as to be able to isolate those infected, or to trace those they have already infected. In two weeks, 1 million people infect 3 million. But, 3 million over two weeks, means that, on average, 200,000 people are infected per day. So, first you need to be able to test 1 million of the initial group, and, on top of that, you need to be able to test a further 200,000 people a day, so as to isolate all of these people, and prevent them spreading it to other people. But, the 200,000 people infected on Day 1, in turn, infect 600,000 people in two weeks, if not isolated, and that amounts to an additional 15,000 people per day. It is clearly impractical to be able to test this number of people per day, so as to identify those infected, and then to be able to trace those they have been in contact with. And, that is really the only point of undertaking such testing. 

For every person you test and find positive, and from there trace 3 other people they have infected, you will have missed another 1,000, 10,000 and so on, because its impossible to test on that scale in the relevant time frame. Moreover, the testing itself is rather pointless. There have been over 100,000 people going into hospital who have been tested for COVID19, but only 10% of them tested positive. The other 90% were suffering from some other flu-like virus that had laid them low. However, having now gone into hospital with these other viruses, they are quite likely then to actually contract COVID19 itself, as the experience of Italy showed, because being in an immune compromised condition already, being put into hospitals where COVID19 is already running rampant, and with inadequate facilities for isolation, lack of protective equipment for staff, and so on, the chances of then being infected are significantly increased, as was the case with people who died in hospital from MRSA, having gone in even for very minor complaints to begin with. 

So, today, for example, it was reported that health workers are to be tested to see if they have COVID19. But, what is the actual purpose? If a health worker, or care worker, does have COVID19, but does not know it, because they are asymptomatic, or have only very mild symptoms, as 80% of the population do, what is achieved by finding out this information. The implication is that such workers would then be sent home for the duration. But, if it turns out that currently 30, 40, 50 or 60% of health workers have the virus, and you send them home, what implication do you think that has for the NHS, as a whole, not just for the care of people with COVID19, but for the care of each and every individual that requires hospital treatment? It would mean that the NHS would collapse, because it could not function with such a depletion of its staff. 

Moreover, as with the rest of the government strategy, it would be idiotic to respond in that way. If an NHS worker or care worker has COVID19, but is asymptomatic, or only has very mild symptoms, there is no need for them not to continue working and providing care. It is only necessary that they have proper PPE, so that they do not infect other members of staff, and, in particular, patients. But, the fact is that all NHS staff, and care workers, should have had adequate PPE from Day 1, so that they did not get infected with COVID19 themselves, and, more importantly, that they did not infect patients, and others in the at risk 20%. The only health and care workers who should have been off work, whether they were ill or not, infected or not, were those that were in the 20% themselves, so that their own health and lives were not put at risk. But, the NHS and care system did not do that from the beginning, because it is grossly understaffed already, as a result of ten years of Tory austerity, and it is short of 100,000 nurses, a situation getting worse because of the idiotic policy of Brexit, which is depriving the NHS of the EU workers it requires. 

As the Oxford Study this week suggests, the actual numbers already infected with COVID19 could be as much as half the population. If that is the case, then the mortality rate estimated by Sir Partick Vallance of 1 in 1000 could itself be a significant overestimation, although it is itself significantly less than the mortality rate that some of the more wild and hysterical suggestions of potential deaths have used. The Glasgow study cited by Wobarg, itself suggests that coronaviruses like COVID19, are part of the general number of flu-like deaths each year, and there is no indication that COVID19 is any more virulent nor deadly than the other coronaviruses that have circulated within the population every other year. Yes, there will be deaths, and the number of deaths, as with flu, will rise or fall from one year to another, but that is not an indication of anything out of the ordinary occurring here. It is no different from the fact that deaths from “flu-like” symptoms were 1600 last year, but 17,000 in 2018, as against an average of 8,000 such deaths per year. 

But, the only way to know the answer to this question, scientifically, is indeed by testing, but not testing to see who currently has the virus, but testing to see who has the antibodies against it, i.e. who has been infected already, whether they knew about it or not. Then we will know what the actual COVID19 mortality rate is, and be able to develop public policy rationally on the basis of it. If, indeed, as the Oxford study suggests half the population, or around 30 million people have already been infected, and have antibodies, then the current number of deaths means that the mortality rate for COVID 19, is perhaps only around 1 in 30,000, or if we assume that the full picture for deaths is not yet apparent, perhaps 1 in 10,000. 

It is necessary to put all of the time and resources for testing into testing for those with antibodies, not just in order to obtain this objective, scientific information about the degree of herd immunity already established, but also because such immunity means that those with these antibodies can go about their business safely, at no risk of again contracting the virus themselves, and, thereby at no risk of passing it on to others.

2 comments:

  1. Boffy

    I have drafted a long reply to this post, in the intervals between my other urgent tasks. Wordpress is rejecting it, rejecting it even being passed to you for moderation.

    It does at least give an error message instead of just losing the comment in the ether. It has more than three times the permitted number of characters. Some of the text (no idea which) is being misinterpreted as HTML.

    So I am about to send it to Jim D, asking him to publish it as a second guest post on Shiraz. How soon Jim is able to do it will depend on his circumstances.

    David

    ReplyDelete
  2. David,

    The character limit is a bit of a pain at 4096 characters. Still its better than the pointless Twitter! But, feel free to do what I do and split your response into several comments, and post them sequentially.

    ReplyDelete