The mystery of the western European 'surge' (which means more daily SARS-Cov-2 positive tests, in absolute terms) continues. France and Spain have both been removed from the 'air bridge' of countries from which travellers entering Britain may do so without quarantine. The recent daily case numbers for the two countries look like this:
However, the daily death rates attributed to Covid look like this:
Both 'surges' are apparently so severe that they are rivalling the original peak in the spring in terms of the number of new cases each day, but there is barely a blip in terms of the number of new deaths reported. Spain shows a pair of large single-day spikes, but this looks like data from delayed reporting due to re-examination of earlier deaths, rather than new deaths as a result of the ongoing case 'surge'. given the fact that they are not against a background of a rising death count in either case.
I know of no good sources for other useful data series relating to the two countries, like the number of tests performed each day, and the number of new hospitalizations of patients with Covid-19 (or, should I say, with positive SARS-CoV-2 tests).
The situation is similar in Britain, although the numbers of new cases are not as high, nor have they grown as quickly as in these two countries. I also know where to look for national and regional data on new hospital admissions for Covid patients and can see that as well as there being hardly anyone dying of Covid in this country at present, our hospitals are also dealing with an extremely small caseload, and have speculated whether this apparently small number may itself be an exaggeration. Now the
Mail has taken notice of it:
Cases are going up... but hospitals are EMPTY because spike in infections is down to younger people | Daily Mail Online
Some speculations and explanations are offered. One I have seen to explain away the lack of a clinical manifestation of the Covid-19 case 'surge' in other European countries: the disease is spreading in populations of young people, who have much lower hospitalization rates than the elderly, although I do not find this satisfactory, as it is not obvious why the virus should be sparing the elderly now. It is also suggested that the virus is now less deadly in Europe due to a genetic change, although this is not supported by genetic evidence. A behavioural reason is suggested, with social distancing and mask usage meaning that people are on average getting smaller infective doses, and so less severe disease, but there are also plenty of encounters happening without social distancing rules, with many people ignoring them, but only falling numbers of deaths.
It is also suggested that perhaps those who are most vulnerable have already died. However, if there are ongoing cases, then there is still susceptibility of the population. It is thought that there is a long-term immunity from Covid, so those among the susceptible population who are catching it could not have had it before now. It would seem statistically improbable that the susceptible population could have already been cleared of the most vulnerable, who are likely to die of the disease. Unless, you could fall susceptible to Covid again on a short time span, and those in the susceptible population have by-and-large already had Covid. However, this is not in accordance with what has been reported in scientific and medical circles about what is known of Covid immunity (i.e. that there broadly is a long-lasting immunity to Covid, and people are not catching the virus for a second time).
What I think should be done is that a cohort of volunteers should be recruited from those testing positive and have them undergo weekly testing to see how for how long they test positive. People are usually tested once and, if positive, are required to isolate for two weeks, and no follow up testing is performed. In settings where follow-up testing has been performed, people have tested positive for up to 55 days, and it could be even more, as there does not seem to be a wealth of research in this area:
Experts question use of repeated Covid-19 tests after a patient recovers
The patient in the above story may have tested positive for even longer than this, it is not known. The rules in her circumstance called for two negative consecutive tests. But what if she tested positive in one in every three tests, say, for a longer period if these tests had been performed? Or one in five tests over an even longer period?
At the population level, follow-up testing is not performed. In those limited circumstances where it is performed, it is usually abandoned after two consecutive negative tests. Someone should really perform a study where they keep testing, and keep testing for a period of months, and not give up after the first consecutive pair of negative tests. The volunteers could be paid for this inconvenience. Although it is difficult to know for sure when someone contracted the virus after testing positive, as the RT-PCR test does not tell you this information. So even if you were to recruit volunteers into this hypothetical study, you have no idea for how long they could have been able to test positive, you only know when their first positive test was (which will in most people be their first test).
Currently we have large numbers of people in Europe who were exposed to Covid in the spring at the peak of the epidemic and were told not to trouble the health systems to ask for a test unless their symptoms were so severe that they had to be admitted into hospital. Now there is all this testing capacity (which is still growing) with not many people left requiring hospitalization, and it is now turning increasingly to community testing, i.e. testing of those younger and less vulnerable people who were told to deal with the illness on their own at home. We know also that the virus can be detected by an RT-PCR test for months after the infection.
I saw a report that said that three quarters of people testing positive for SARS-CoV-2 in France currently are asymptomatic. This could be post-symptomatic in many cases. The possible symptoms for Covid-19 are so vague, being the same in many cases for a multitude of other endemic viral and bacterial infectious diseases, that the presence of symptoms and a corresponding positive SARS-Cov-2 test are not in themselves enough evidence to diagnose Covid-19 at this point in countries like France, Spain, or the United Kingdom. Someone could have caught SARS-CoV-2 months ago, got over it, still be shedding enough viral fragments to have a good chance of testing positive with an RT-PCR test, and have in the meantime caught another cold or flu virus, or similar, and have symptoms from that (or even from hay fever).