AD1184
Celestial
I think the state of the epidemic in England is better than some imagine. There are lots of concerns in the media about a second wave of Covid, and a reported recent uptick in cases. Looking at the data for London we see the following about the number of new cases and about the number of people who are going into hospital:
Coronavirus (COVID-19) in the UK
We see a recent rise in people testing positive. The increase in cases has not been accompanied by a similar increase in new hospitalizations. Earlier in the epidemic, the cases were known about primarily because people were turning up in hospitals with symptoms and testing positive for the virus in that setting. Nowadays, far more cases are being detected 'in the community' while the numbers of people being admitted into hospital keep trending downwards.
This suggests a few possibilities. I thought earlier on that maybe the lengthening of the day had something to do with it as people get more vitamin D, because of the falling numbers in new cases and the low antibody prevalence. However, the subsequent accelerating spread in the southern United States and other locations suggests that this is likely not the reason.
Another possibility is that London has attained, or is close to attaining, herd immunity. London was hit hard and early by the pandemic and did a poor job of managing the spread of the disease. It may be the case, according to some recent reports, that circulating common cold viruses may confer an immunity to a significant proportion of individuals such that the threshold for getting herd immunity to Covid may be significantly lower than the 60-80% of the population assumed initially.
https://medicalxpress.com/news/2020-08-exposure-common-cold-coronaviruses-immune.html
Furthermore, it is known that antibodies are not the whole story when it comes to viral immunity or for determining how many people have had the virus. Antibody presence may be undetectable in some people, or may have only a limited window of detectability. Mass antibody testing kits also have reliability issues.
The seroprevalence of Covid-specific antibodies peaked among blood donors in London at around 16% in mid-May:
https://assets.publishing.service.g...ID19_Surveillance_Report_week_31_FINAL_V2.pdf
If antibody prevalence were the be-all and end-all of Covid immunity, then you would expect a rising susceptibility of Londoners to Covid currently, more large outbreaks and more people going into hospital with the virus. As it is, these things are not happening. It is also known that some people have a primarily T-cell mediated immune response instead of an antibody one, which is much more difficult to detect. It is therefore the case that the true cumulative spread of Covid throughout the population in London is unknown, but certainly higher than the antibody seroprevalence studies would suggest.
What is also the case is that someone can test positive on a RT-PCR test for Covid (the most common testing method) long after they have got over the virus, perhaps months after the initial infection. More tests are being performed in new testing centres, and the criteria for getting a test are being made less strict. These facts could explain the noted rise in positive tests. i.e. The Trumpian explanation of more tests equalling more cases may apply to London (and England more broadly). It would likely also apply to certain places in the US like New York, but not everywhere. As I keep saying, every locality is in its own phase of the Covid epidemic.
There may not be second waves after all. What constitutes a second wave is fairly arbitrary, as the term is ill-defined. But I would take a second wave to be a resurgence of the disease in an area that has already had a severe London- or New York-scale epidemic. I would not consider an area which locked down early before there were many infections, relaxed its lockdown and then saw infections start to climb again to be going through a second wave. It is an interrupted first wave. If someone is bleeding out of an artery and a tourniquet is applied to stem the bleeding, when you relax the tourniquet and bleeding resumes that is not a second wound, it is still the first wound. I have not yet seen evidence of a second wave in any of the badly affected parts of the world. If people who had the virus before start to demonstrably become infected again in an area then that would be a clear sign of a second wave.
Coronavirus (COVID-19) in the UK
We see a recent rise in people testing positive. The increase in cases has not been accompanied by a similar increase in new hospitalizations. Earlier in the epidemic, the cases were known about primarily because people were turning up in hospitals with symptoms and testing positive for the virus in that setting. Nowadays, far more cases are being detected 'in the community' while the numbers of people being admitted into hospital keep trending downwards.
This suggests a few possibilities. I thought earlier on that maybe the lengthening of the day had something to do with it as people get more vitamin D, because of the falling numbers in new cases and the low antibody prevalence. However, the subsequent accelerating spread in the southern United States and other locations suggests that this is likely not the reason.
Another possibility is that London has attained, or is close to attaining, herd immunity. London was hit hard and early by the pandemic and did a poor job of managing the spread of the disease. It may be the case, according to some recent reports, that circulating common cold viruses may confer an immunity to a significant proportion of individuals such that the threshold for getting herd immunity to Covid may be significantly lower than the 60-80% of the population assumed initially.
https://medicalxpress.com/news/2020-08-exposure-common-cold-coronaviruses-immune.html
Furthermore, it is known that antibodies are not the whole story when it comes to viral immunity or for determining how many people have had the virus. Antibody presence may be undetectable in some people, or may have only a limited window of detectability. Mass antibody testing kits also have reliability issues.
The seroprevalence of Covid-specific antibodies peaked among blood donors in London at around 16% in mid-May:
https://assets.publishing.service.g...ID19_Surveillance_Report_week_31_FINAL_V2.pdf
If antibody prevalence were the be-all and end-all of Covid immunity, then you would expect a rising susceptibility of Londoners to Covid currently, more large outbreaks and more people going into hospital with the virus. As it is, these things are not happening. It is also known that some people have a primarily T-cell mediated immune response instead of an antibody one, which is much more difficult to detect. It is therefore the case that the true cumulative spread of Covid throughout the population in London is unknown, but certainly higher than the antibody seroprevalence studies would suggest.
What is also the case is that someone can test positive on a RT-PCR test for Covid (the most common testing method) long after they have got over the virus, perhaps months after the initial infection. More tests are being performed in new testing centres, and the criteria for getting a test are being made less strict. These facts could explain the noted rise in positive tests. i.e. The Trumpian explanation of more tests equalling more cases may apply to London (and England more broadly). It would likely also apply to certain places in the US like New York, but not everywhere. As I keep saying, every locality is in its own phase of the Covid epidemic.
There may not be second waves after all. What constitutes a second wave is fairly arbitrary, as the term is ill-defined. But I would take a second wave to be a resurgence of the disease in an area that has already had a severe London- or New York-scale epidemic. I would not consider an area which locked down early before there were many infections, relaxed its lockdown and then saw infections start to climb again to be going through a second wave. It is an interrupted first wave. If someone is bleeding out of an artery and a tourniquet is applied to stem the bleeding, when you relax the tourniquet and bleeding resumes that is not a second wound, it is still the first wound. I have not yet seen evidence of a second wave in any of the badly affected parts of the world. If people who had the virus before start to demonstrably become infected again in an area then that would be a clear sign of a second wave.