Until very recently, I had a rather simplistic view of the progression of the current pandemic, blithely assuming that the first and second waves were caused by the original Wuhan strain, which was replaced by the 50% more infectious Alpha variant that dominated the third wave and which is now being replaced in turn by the 60% even- more- infectious Delta variant. The reality, as illustrated by this graph of how a succession of variants displaced each other in Switzerland, is far more complex, requiring a more nuanced understanding than has thus far been demonstrated by the provincial premiers whose consistently poor decisions have cost many thousands of Canadians their lives.
Viruses are a very different form of life than our species and those with which we are familiar. Whereas we have enzymes which ensure the accurate copying of our genes, viruses thrive by adapting not just to the differing environments within each species and individual which they infect, but to the changing responses of each host’s immune system during the course of an infection. With roughly two new generations every day during which a host is infected, viruses epitomize blindingly rapid natural selection. And whenever two or more variants infect the same cell at the same time, their respective genes are essentially reshuffled, spawning still newer variants.
Variants and selection pressures
Natural selection operates on the differing traits which manifest underlying genetic differences, some of which make the organism more “fit“ for the challenges of whatever environment it finds itself in, with fitness being defined as successfully passing on those genes to the next generation. Where their hosts happen to be modern humans who respond to a pandemic by both changing their and developing protective vaccines, those changes favour the variants whose genes allow them to best circumvent each new selection pressure. It’s those particular variants which can best infect new people, and which therefore displace their predecessors by dominating new cases.
Vaccines as a selection pressure
The major reason that Canada has fared so badly since the second wave is that the Premiers of our most-afflicted provinces are all former businessmen who, in sharp contrast to the Ernie Eves government which helped suppress the 1963 SARS outbreak, chose to base public health decisions on their own political predilections rather than relying on the experts. Never really understanding the degree to which pandemics are moving targets and with deeply-ingrained reluctance to impose restrictions on businesses, they consistently waited too long to impose shutdowns when rates of new cases were rising and then eased them as soon as the numbers started falling, thereby triggering the next wave. Characteristically, they have viewed a single dose of vaccine as a panacea which would allow life to return to normal. Given that partial immunity serves as a strong selection pressure, it was inevitable that first variant to come along with a degree of vaccine resistance would rapidly become the dominant strain. That of course is the Delta variant. In the UK, a third of new cases are people with single-dose vaccination. Thus far, the only fully-vaccinated people who have been infected appear to be those with compromised immune systems or have been under high chronic stress. We currently have some four million actively infected people on this planet, each of whom is a potential incubator of still newer variants. As full vaccination becomes the strongest selection pressure, it’s too much to hope that the next round of variants won’t evolve traits to circumvent that protection.
Where do we go from here?
Kingston’s highly effective Medical Officer of Health, Dr. Kieran Moore, who is now Ontario’s new Chief Medical Officer last week expressed the hope that full vaccination would by September allow COVID to be treated as an “endemic” rather than pandemic disease, with life for most Ontarians getting back to normal. That, of course, depends on the dangers of future variants to those fully vaccinated, which is frankly unknowable at this point. The track record to date of this coronavirus suggests that it will continue to change sufficiently rapidly that new vaccines will have to be developed, tested and deployed with equal rapidity to avoid returning to a pandemic state. An excellent article in the July Scientific American highlights several groundbreaking technologies which leave me cautiously optimistic that science will be up to the challenge. Now, if it were only that easy to upgrade our political system …