What Comes After Delta?

Posted on | August 25, 2021 | 2 Comments

Mike Magee

“Many still see Alpha and Delta as being as bad as things are ever going to get. It would be wise to consider them as steps on a possible trajectory that may challenge our public health response further.”
Aris Katzourakis, Evolutionary Biologist, University of Oxford.

In my Jesuit high school, we were offered only one science course – chemistry. I took it in my Senior year and did pretty well. In contrast, I took four years of Latin, and three years of Greek, as part of the school’s Greek Honors tract.

Little did I know that Covid would create a pathologic convergence of sorts six decades later. Let’s review the Covid mutants:

Alpha – A variant first detected in Kent, UK with 50% more transmissibility than the original and has spread widely.

Beta – Originating in South Africa and the first to show a mutation that partially provided evasion of the human immune system, but may have also made it less infectious.

Gamma – First detected in Brazil with rapid spread throughout South America.

Delta – First seen in India with 50% more transmissibility than the Alpha variant, and now the dominant variant in America and around the world.

Our ability to track and identify mutating viruses in real time is now extraordinary. Over 2 million Covid genomes have been cataloged and published. But describing the “anatomy” of the virus is miles away from understanding the functional significance of their codes, or the various biochemical instructions they may instruct.

These deeper questions are in the realm of evolutionary biologists who are currently experiencing sleepless nights. Their recurrent nightmare? “What comes after Delta?”

What they know already is that Delta’s genetic mutation, P681R, affected a spot on the virus spike that cuts through protein chains and sped up human cell entry 1000 times. The speed lit a fuse under colony growth, which in turn allowed the virus’s spread to other unsuspecting human contacts before any immune response generated symptoms appeared. Of course the state of being asymptomatic didn’t last for long. Speedy virus multiplication rates accelerated the microbes movement from upper airways to lower airways leading to hospitalization rates that are twice as common as they were in the original Covid.

What’s next in the Greek alphabet? First a few basics.

1. A virus’s survival, and threat to us, relies on three factors:

a)Infectiousness, b) Virulence, c) Immune Evasion.

But these factors can as easily play against each other as for each other. Natural or vaccine induced immunity slows down infectiousness and potential virulence. But (by narrowing a virus’s options for survival) it also creates a Darwinian reward for any mutant that figures out the Rubik’s Cube solution to becoming “invisible” to the human immune system. According to Rockefeller University virologists, such a change requires the coalescence of 20 independent random changes in the genome. Bottom line: Random escape is a tall order. But under the current system, with Delta transmissibility likely to eventually burn through most of its potential future victims, such a change would be richly rewarded.

2. Viruses depend on us. But we no longer look or act as we did in 2019. Two billion citizens worldwide have had at least one dose of the vaccine, and hundreds of millions of others have survived the infection. The virus each day is increasingly pressured to find its next human victim. One way out is to figure a way past our immune defenses provided by prior infection or vaccination.

So this is a cyclical game, likely to go on for some time. If we global citizens play our vaccination cards right, the virus has fewer turns in the game, and is less likely to draw the cards it needs to evade our human defenses.

So here are five take-away facts:

The longer we allow Covid to stick around, the worse this could get.
The majority of the messy replication mistakes are inconsequential, but there are occasional windfalls that rise to Greek alphabet mythical status.
Delta’s critical weakness – it leaves behind high antibody titers that limit its future.
Give the virus more time, or access to compromised hosts, and anything can happen. Viruses are constantly rolling the evolutionary dice.
Mutations hurt us by increasing transmissibility/virulence or immune evasion. The good news is there is some evidence that an immune escaping Covid might not be efficiently transmissible any more.

A guy like Ron DeSantis is not only ignorant of evolutionary biology, he’s playing with fire – and with our human lives. This cannot go unchallenged. Whatever it takes, we need to force this virus into a corner. Otherwise, we run the risk of becoming a Greek tragedy ourselves.

Comments

2 Responses to “What Comes After Delta?”

Lawrence Williams
September 10th, 2021 @ 10:47 pm

Politicians like Ron DeSantis who block medically endorsed methods of preventing the spread of Covid should be arrested and charged with criminal negligence in exposing millions of people of all ages to the much higher risk of sickness, hospitalization, and death. If law enforcement in their own states will not make the arrests then we need to find a way for the Justice Department through the FBI to take such action. Children are dying unnecessarily and that is criminal.
Mike Magee
September 11th, 2021 @ 1:53 pm

Larry-
Your lawyerly analysis always speaks with clarity and truth. Best, Mike