As the brand new coronavirus was quickly spreading in February and March 2020, many governments launched stringent lockdown measures. By means of an enormous public effort, these international locations have been profitable at slowing the pandemic.
Combining varied public well being approaches, international locations reminiscent of Slovenia and New Zealand have eradicated the virus inside their borders. Different international locations, 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 international locations the place stringent social distancing measures have been utilized. Governments, in addition to the general public, at the moment are eager to start out eradicating the restrictions and return to regular life.
With the comfort of the lockdown guidelines, warnings are being sounded a couple of potential resurgence of COVID-19 circumstances – a so-called second wave. The second wave of the Spanish flu pandemic in 1918-20 was notably devastating, as was the second wave of the H1N1 epidemic in 2009-10. So what might be accomplished to keep away from a second wave of COVID-19?
For the virus to unfold, it wants a provide of prone and contaminated hosts and a profitable transmission. These elements are conveniently captured by the replica quantity, R, the common variety of new circumstances attributable to one contaminated particular person. A price of R above one means the variety of circumstances is growing, whereas beneath 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 reminiscent of China, South Korea, New Zealand, the UK and most European international locations, have now lowered this worth to beneath one. In different international locations, reminiscent of 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 instance how the second wave may seem.
So long as there are prone and contaminated individuals within the inhabitants, the virus can unfold. Proof is accumulating that the primary wave of the epidemic resulted in solely restricted immunity, nicely beneath herd immunity ranges. There are additionally pockets of a inhabitants by which the virus not solely survives however continues to unfold. The transmission in care houses now accounts for a big share of circumstances in lots of international locations.
Because the lockdown measures are relaxed, individuals are beginning to work together extra. This may lead to elevated values of R. However it’s important that the worth of R is saved beneath or equal to 1, as proven within the diagram beneath.
However even a comparatively modest change of R to 1.2 would lead to a big outbreak inflicting the second wave, demonstrating how vital it’s to get the management measures proper.
Response to the second wave requires recurrent lockdown measures, as proven beneath. However whereas society has to this point obeyed the restrictions remarkably nicely, lockdown fatigue may make it harder to impose such strict insurance policies once more.
The epidemic may proceed into autumn and winter when seasonal flu could be prevalent. Whereas it seems that the SARS-CoV-2 virus will not be strongly affected by climate, the healthcare system may change into overwhelmed if COVID-19 and the flu strike on the identical time.
On the plus facet, preventive measures aimed toward SARS-CoV-2 virus (reminiscent of masks and handwashing) may cut back the unfold of the flu virus.
Lastly, the virus may mutate leading to a extra infectious pressure. Such a mutation might need prompted the second center wave of Spanish flu to be notably 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 extensively by vaccination.
Within the close to future, governments might want to delicately steadiness 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 parts of the technique. Epidemiological fashions and ideas like R can assist in establishing the place, how, when and for a way lengthy, the federal government must intervene to stop the second wave.
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