These Eventualities Present What a Second Wave of COVID-19 Might Look Like

As the brand new coronavirus was quickly spreading in February and March 2020, many governments launched stringent lockdown measures. By a large public effort, these nations have been profitable at slowing the pandemic.

Combining numerous public well being approaches, nations corresponding to Slovenia and New Zealand have eradicated the virus inside their borders. Different nations, together with the UK, achieved important progress in arresting the unfold of the illness.

But the lockdown has led to substantial financial and social loss in nations the place stringent social distancing measures have been utilized. Governments, in addition to the general public, at the moment are eager to begin eradicating the restrictions and return to regular life.

With the relief of the lockdown guidelines, warnings are being sounded a few doable resurgence of COVID-19 circumstances – a so-called second wave.

The second wave of the Spanish flu pandemic in 1918-20 was significantly devastating, as was the second wave of the H1N1 epidemic in 2009-10. So what will be carried out to keep away from a second wave of COVID-19?

(Public Area)

For the virus to unfold, it wants a provide of prone and contaminated hosts and a profitable transmission. These components are conveniently captured by the copy quantity, R, the common variety of new circumstances brought on by one contaminated particular person.

A price of R above one means the variety of circumstances is growing, whereas under one they’re declining. Earlier than the lockdown, the worth of R for the coronavirus was estimated to be between two and 4.

International locations corresponding to China, South Korea, New Zealand, the UK and most European nations, have now lowered this worth to under one. In different nations, corresponding to Sweden or Russia, the worth of R stays close to or above one, reflecting the rise within the variety of circumstances.

The connection between the inhabitants behaviour and the worth of R is difficult, however we are able to nonetheless use this idea as an example how the second wave may seem.

Simulation particulars can be found right here. (Adam Kleczkowski)

Above: Single wave epidemic. The highest graph reveals the time dependence of the mannequin copy quantity. The underside graph reveals the anticipated variety of circumstances. The preliminary worth of R is 2.7 and drops to zero.eight with the lockdown.

So long as there are prone and contaminated folks within the inhabitants, the virus can unfold. Proof is accumulating that the primary wave of the epidemic resulted in solely restricted immunity, effectively under herd immunity ranges.

There are additionally pockets of a inhabitants during which the virus not solely survives however continues to unfold. The transmission in care properties now accounts for a big proportion of circumstances in lots of nations.

Because the lockdown measures are relaxed, persons are beginning to work together extra. This may end in elevated values of R. However it’s essential that the worth of R is saved under or equal to at least one, as proven within the diagram under.

Extra particulars right here. (Adam Kleczkowski)

Above: Single wave epidemic with rebound attributable to lockdown leisure. The preliminary worth of R (high graph) is 2.7 and drops to zero.eight with the lockdown, however goes again to 1 as lockdown measures are relaxed.

However even a comparatively modest change of R to 1.2 would end in a big outbreak inflicting the second wave, demonstrating how vital it’s to get the management measures proper.

Extra particulars right here. (Adam Kleczkowski)

Above: Second wave. The preliminary worth of R (high graph) is 2.7 and drops to zero.eight with the lockdown, however goes again to 1.2 as lockdown measures are relaxed.

Response to the second wave requires recurrent lockdown measures, as proven under. However whereas society has to this point obeyed the restrictions remarkably effectively, lockdown fatigue may make it tougher to impose such strict insurance policies once more.

Extra particulars right here. (Adam Kleczkowski)

Above: A state of affairs involving a number of outbreaks and lockdown intervals. The worth of R (high graph) is periodically elevated to 1.2 as lockdown is relaxed after which falls again to zero.eight as it’s imposed once more.

The epidemic may proceed into autumn and winter when seasonal flu may be prevalent. Whereas it seems that the SARS-CoV-2 virus shouldn’t be strongly affected by climate, the healthcare system may grow to be overwhelmed if COVID-19 and the flu strike on the identical time.

On the plus facet, preventive measures aimed toward SARS-CoV-2 virus (corresponding to masks and handwashing) may scale back the unfold of the flu virus.

Lastly, the virus may mutate leading to a extra infectious pressure. Such a mutation might need brought about the second center wave of Spanish flu to be significantly extreme.

If one thing comparable occurred for SARS-CoV-2 virus, the ensuing epidemic would dwarf the present outbreak even when the brand new R worth was solely 4, in contrast with 10-12 for mumps or 12-18 for measles. Mumps and measles are solely saved from spreading broadly by vaccination.

Extra particulars right here. (Adam Kleczkowski)

Above: Massive autumn wave. The worth of R (high graph) is elevated to four for a brief interval in November. Notice the modified variety of circumstances in comparison with different graphs.

Within the close to future, governments might want to delicately stability the wants of the financial system and social life with suppressing the unfold of the virus. Take a look at, hint and comprise and native responses are key components of the technique.

Epidemiological fashions and ideas like R may also help in establishing the place, how, when and for the way lengthy, the federal government must intervene to stop the second wave.

Adam Kleczkowski, Professor of Arithmetic and Statistics, College of Strathclyde.

This text is republished from The Dialog underneath a Artistic Commons license. Learn the unique article.