At the outset, the potential of Coronavirus to cause widespread rampage and then deceive scientists by mutating itself was not manifest to the scientific community. While the scientists were aware of viruses mutating but they did not anticipate that COVID19 would turn into a formidable foe so quickly. For much of 2020 most experts were not particularly worried about the virus’s ability to evolve but in the late fall it jumped and there emerged distinctive new versions of the virus sparked alarming surges in many places particularly Brazil, South Africa and the United Kingdom.
Within no time variants became a global preoccupation as they carry not one but a slew of mutations possessing the uncanny abilities to fatally attack many aspects of immunity. Their sudden emergence caught scientists off guard and set the stage for the next chapter of the pandemic. The mass vaccination campaign that could have felt like a wave of relief is instead an ominous, urgent race against a changing virus. The path to herd immunity, the powerful milestone when the virus would not be able to spark new outbreaks, is looking longer and more complex. Vaccines may not totally vanquish but simply chase a continually changing virus.
As scientists work to get a handle on the variants, the situation gives the public a rare front-row seat and real-time view of the unpredictability of viral evolution. The virus is changing and scientists are preparing for a wide range of possible futures. Already, researchers are increasing genomic surveillance to track changes to the virus and are building maps of the genetic escape routes the virus could take so that when mutations inevitably arise, scientists can quickly interpret whether they are likely to pose a threat. That does not necessarily mean a world where the pandemic never ends as the outlook is improving as vaccines are rolled out and if vaccines become outdated, they will be updated.
In laboratories, scientists are testing whether the current variants remain susceptible to antibodies conjured by natural infection and vaccines. Companies are preparing new versions of vaccines and testing extra booster shots, just in case. The stealthy, speedy arrival of variants has put scientists in the familiar position of being unable to predict where the virus is headed. The past few months have been a wake-up call warning that human race is not clever than evolution itself.
Interestingly, even before the variants emerged, there were hints that scientists had been underestimating the virus’s capacity to change. Instead of just one or two genetic tweaks, the virus accumulated 21 mutations and they were concentrated in the spike protein — the spot where the immune system trains much of its firepower to block infections. One of its genetic changes reduced the virus’s susceptibility to antibodies but also carried a potential Achilles’ heel, making it less efficient at infecting cells. A second change — a missing portion of the genome — seemed to compensate, increasing the virus’s ability to infect cells.
Many scientists had assumed that because the virus had a proofreading mechanism to correct errors when it multiplied, it would not mutate rapidly but the changes in the virus were not typos in the genetic code — they were missing swaths called deletions. The virus could not proofread what was not there. Scientists know that viruses make copies of themselves in people’s cells and they make occasional errors in the process. When infections resolve quickly and mutations accumulate slowly, that does not give the virus much chance to cultivate a huge reservoir of genetic diversity.
With the virus infecting more than 100 million people across the planet, it was given maximal opportunities to change disguise. It suggests that there is an evolutionary jump from some hidden source of viral evolution. One can detect a blind spot in the community where the evolution is happening and it cannot be seen until it spreads wider. Not every mutation turns a virus into a super-villain as most have little effect or might actually hobble the virus. And even mutations that seemingly work to the benefit of the virus can come with trade-offs. A genetic tweak that allows the spike protein to fly under the immune system’s radar a bit more stealthily might seem unequivocally helpful to a virus but a change like that could also backfire, making it less efficient at breaking into the body’s cells. A virus that is invisible to the immune system sounds fearsome but it could be inept in critical ways.
One of the open questions about the evolutionary capacity of the coronavirus is whether there is a limit to its ability to change. The spike latches onto cells, like a key fitting into a lock. Many scientists had assumed that if that key changed too much, it would not be able to open the door anymore. Yet there were warnings about the spike’s propensity for shape-shifting before the variants.
What scientists are debating now is where the virus could be headed next. It could be in a period of rapid evolution, in which the virus is adapting to get better at infecting people. After some amount of time that rate could slow down. Or the virus, like influenza, could simply be in a constant back-and-forth with the immune system. The immediate implications for ordinary people are not dire. It remains important to bring down transmission to give the virus fewer chances to change — and for people to get vaccinated but for scientists there is a long path ahead. Companies and scientists are already beginning tests of revamped vaccines, so that they will be ready if they are needed. TW