A Winter of Discontent? The Seasonality of the Coronavirus & the Threat Ahead
Drawing on the latest research, Robert C Palmer warns of a perfect storm this winter as complacency meets a resurgence of SARS-CoV-2
With Israel becoming the first country in the world to impose a second national lockdown, Spain setting a pandemic record for new cases in a day (12,183) and France recording around 10,000 new cases daily, a vastly unreported transmission issue needs our full attention: the seasonality of coronaviruses.
The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes Coronavirus Disease 2019 (COVID-19) continues to test global medical health systems. A combination of factors that are destined to collide during the autumn and winter periods are likely to intensify matters, to a point that the after-effects of the first wave of infections will be eclipsed.
Disjointed, politically stimulated strategies are this virus’s best friend. Give it an inch, it will take a mile
The situation is still deteriorating, and evidence is mounting that this strain of Coronavirus, like its genetic relatives, will have a winter seasonal resurgence in temperate regions, where over 60% of the global population resides. When the pandemic is finally over, it has been projected that SARS-CoV-2 will then become endemic and settle into annual seasonal circulation within the global community.
The short-term lower prevalence, incidence and reproduction number (R0) associated with the infection control efforts since lockdown were evidently aided by the seasonal variation of the virus. Combined they provided a window of opportunity for better preparation of health care systems that has been missed.
When SARS-CoV-2 first struck it was originally thought that the virus would mimic its closest genetic relative, SARS-CoV-1 (that caused the SARS pandemic in 2003) and could be eradicated by intensive non-pharmaceutical interventions (NPIs) – such as physical distancing, testing and tracing, and quarantine – after a short-term but, nevertheless, severe outbreak.
As the pandemic has unfolded, public health authorities increasingly believe this not to be the case. As SARS-CoV-2 is a beta coronavirus it is now understood to likely mirror the seasonality of its genetic relatives, particularly in temperate regions.
Models with plausible parameters have predicted that we have just passed a small peak (in temperate regions of the Northern Hemisphere) and are poised for a larger peak in winter 2020/2021
Global fleeting reductions in epidemiological measures over the summer suggest that both infection control measures (such as social distancing) and seasonal variations were successful in reducing infections, but this did not mean the pandemic was contained.
Seasonal variation appears to be missing from the conversation when assessing the summer reduction in R0, incidence and prevalence (a vital measure in healthcare planning). The same can be said about the possible impact of seasonal forcing on top of the recent rise in SARS-CoV-2 cases, despite an early study stating: “The onset of spring and summer could give the impression that SARS-CoV-2 has been successfully contained, only for infections to increase again in 2020-2021 winter season”.
Since then other studies suggest the transmission dynamics of SAR-CoV-2 are such that it is likely that there will be a winter seasonal ‘forcing’ of the virus.
October and November Peaks
Models with plausible parameters have predicted that we have just passed a small peak (in temperate regions of the Northern Hemisphere) and are poised for a larger peak in winter 2020/2021. This would mirror what happened during the 1918 Spanish Flu pandemic, where a second more devastating wave came in the winter after social distancing had been relaxed after the first wave.
With the available data, and if the prediction that SARS-CoV-2 will follow a similar seasonal pattern to its seasonal coronaviruses (sCoVs) cousins is correct, the Human coronaviruses (HCoVs) OK43 and HKU1 effective reproduction number (the basic reproductive number (R0) and the fraction of the host population that is susceptible) reaches its peak between October and November, which then slowly wanes between February and May.
Based on that evidence, this point in time (mid-September) would be too early for seasonal forcing to have already begun proper. A conclusion can therefore be drawn that the relaxation of lockdown measures; the lack of aggressive (app-based) testing and tracing; and, individual/collective behaviour are responsible for the current rise in infections.
If the seasonal variation of SARS-CoV-2 indeed follows that of its relatives, it means that when the pandemic struck Europe in March, the effective reproduction number (associated with winter forcing) had already entered its trough period and can be considered to have attributed to a reduction in cases and deaths after May, alongside the NPIs imposed during lockdown.
Fast-forward to September. There is now a marked rise in R0, COVID-19 cases, and more deaths are being reported. As behavioural changes and the relaxation of NPIs are creating a new wave of infections, come October, the seasonal forcing pattern will have the opposite effect to that in March. It will simply exacerbate matters.
Resurgences this autumn or winter (seasonal or behavioural) would come when the rate of public susceptibility of contracting COVID-19 – following months of lockdowns and strict social distancing measures – will be high. For the same reason, levels of immunity will be very low in the community, especially as NPIs are about to be upscaled once more.
The Strain on Health Services
The likelihood of a scenario where a seasonal resurgence of transmissions in temperate climates is becoming increasingly clear and both post- and pre-COVID-19 research indicates that winter resurgences in those regions will coincide with seasonal reoccurrences of human coronaviruses (HCoVs) already in long-term circulation, and when influenza and respiratory syncytial viruses (RSVs) return, and then, reach their subsequent mid-winter peak
The combination of existing sCoVs, influenza, RSVs, and SARS-CoV-2 would be devastating for morbidity and mortality and a serious strain on public health services. If we consider what we are currently witnessing i.e. what appears to be the start of another exponential rise in COVID-19 cases, as a study in July in the Journal of Infectious Diseases explained: “the implications of such a combination will inevitably cause a substantial increase in the demand to healthcare system resources during wintertime”.
“A key metric for the success of social distancing is whether critical care capacity is exceeded” a study in The Lancet has concluded: seasonal forcing of all these viruses at the time of high incidence and prevalence of SARS-CoV-2 would expose physical distancing measures to date as a failure. Most of the sacrifices made – until now – will have been for nothing if protecting public health and the economy were their goal.
There is much confused messaging about herd immunity, and it is unlikely to be achieved without a vaccine. Despite the evidence suggesting that COVID-19 is a good candidate for finding a vaccine, nothing is certain and the timescale unclear.
As things stand, it is not clear how long any immunity to SARS-CoV-2 could last and it is not yet known if the presence of antibodies provides long-term immunity to COVID-19. In contrast, a study found that the antibody-rich plasma found in people who have recovered from COVID-19 does not contain high enough levels of antibodies that can neutralize viral infectivity. Research also confirms that immunity to seasonal coronaviruses wanes within a year.
This is a global phenomenon and must be treated as such. Disjointed, politically stimulated strategies are this virus’s best friend. Give it an inch, it will take a mile. Governments in temperate regions must work together – driven by the available science – in their efforts to suppress the virus, and their citizens prepared to adapt to a new way of life, at least for the time being.
Social distancing is projected to be with us until 2022 and civil liberties are set to be curtailed to an extent and for a duration yet to be prescribed.
The complacency we are witnessing now at both a government and community level – when compounded with the transmission dynamics of these seasonal viruses – have created the conditions for a perfect storm to hit the UK over the next few months. If the Government and individuals continue to fail to take the situation seriously – from this moment – a winter of discontent will likely follow a summer of lost opportunities.
Dr. Robert C. Palmer is a lecturer in law at the Open University Faculty of Business and Law and has a science background in physics and nautical sciences
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