Viruses mutate as they get passed around. The original strain of the coronavirus existed in a bat and probably made its way into another animal host where it picked up new features that allowed it to become highly infectious to humans. Now a new study which was pre-published last week, meaning it hasn’t been peer-reviewed yet, claims the virus has mutated, making it even more infectious to humans than the original strain.
The new strain appeared in February in Europe, migrated quickly to the East Coast of the United States and has been the dominant strain across the world since mid-March, the scientists wrote…
The mutation identified in the new report affects the now infamous spikes on the exterior of the coronavirus, which allow it to enter human respiratory cells. The report’s authors said they felt an “urgent need for an early warning” so that vaccines and drugs under development around the world will be effective against the mutated strain.
Wherever the new strain appeared, it quickly infected far more people than the earlier strains that came out of Wuhan, China, and within weeks it was the only strain that was prevalent in some nations, according to the report. The new strain’s dominance over its predecessors demonstrates that it is more infectious, according to the report, though exactly why is not yet known.
If confirmed, this might help explain a number of things we’ve all witnesses. For instance, the northeastern United States has been much harder hit than the west coast even though the west coast had some of the first hot spots. That could be because the west coast was initially dealing with the Wuhan strain while the east coast was hit with the more infectious European strain.
These results could also help explain some of the international differences we’ve seen. For instance, China was able to stop the first wave of the virus in Wuhan while places like Spain and Italy, who were dealing with the new strain, struggled to achieve the same results. Maybe the difference in partly based on China dealing with a less infectious strain of the virus.
Or maybe not.
An associate professor from Harvard’s school of public health published a thread about this study last Friday suggesting that the opposite could be the case: Maybe it only appears the European strain is more infectious because it spread more successfully in a place where mitigation efforts were insufficient.
Major observation: a specific mutation in the spike protein of the virus has been in a higher fraction of cases as the pandemic has worn on in multiple places. Given the role of the spike protein in entry of the virus to cells this might be reasonable. Now for the cold water 2/n
— Bill Hanage (@BillHanage) May 2, 2020
by that, I mean this variant might have been lucky and got introduced to places outside Wuhan and different approaches to social distancing early on. It's not about the virus, it's the environment and the opportunities for transmission 4/n
— Bill Hanage (@BillHanage) May 2, 2020
The blue mutation is already found in close to 100% of the cases of the early outbreak in North Italy. This might be selection. It might well also be chance, the lucky strain that got out of China. Most outbreaks around the world descend from Europe now 6/n
— Bill Hanage (@BillHanage) May 2, 2020
WA was alerted early on through outbreaks in healthcare. It put in serious controls at local and state levels. The orange variant arises, and is followed by the blue (coming in from the east coast and Europe) yet both decline at roughly the same rate 13/n
— Bill Hanage (@BillHanage) May 2, 2020
So maybe what looks like a more infectious strain to us is really just a reflection of less intensive mitigation efforts in nations, like Italy, where this particular variation spread. That answer isn’t as satisfying in some ways but it could be true. The fact that this research hasn’t been peer-reviewed and could be explained in other ways just means we should probably take it with a grain of salt for now.
Update: A virologist from Colombia University is also dumping on the study.
This type of reporting on #SARSCoV2 #COVID19 #coronavirus makes my blood boil. There is no evidence that the dominant strain is such because it is "more contagious"https://t.co/IesYkQetSS
— Dr. Angela Rasmussen (@angie_rasmussen) May 5, 2020
The old adage that correlation does not equal causation applies here. If you are looking at sequence data alone, you can't show effect that this single mutation, spike D614G has on transmission. This means that a mutation at position 614 in spike changed aspartic acid to glycine.
— Dr. Angela Rasmussen (@angie_rasmussen) May 5, 2020
Importantly, these studies actually did experiments to show that A82V increased infectivity (the ability to infect cells) in surrogate systems (not actual Ebola virus). Claims about A82V's function in infection and pathogenesis were not made based solely on sequence data.
— Dr. Angela Rasmussen (@angie_rasmussen) May 5, 2020
In cell culture, the A82V mutation did appear to improve viral fitness (the overall ability of the virus to infect cells and replicate), which may explain why this emerged early in the epidemic and there was selection pressure to maintain the A82V change.https://t.co/wPWwMB1zoR
— Dr. Angela Rasmussen (@angie_rasmussen) May 5, 2020
And for Ebola GP A82V, these conclusions were based on a number of rigorous, well-controlled experiments conducted by teams of respected virologists. Spike D614G from #SARSCoV2 has not ever been tested in a single experiment. This is based solely on computational analysis.
— Dr. Angela Rasmussen (@angie_rasmussen) May 5, 2020
Spike D614G may well have functional importance. It may even increase transmissibility. But we won't know until this is tested experimentally. There's no basis for the breathless OMG #SARSCoV2 HAS MUTATED TO BE MORE TRANSMISSIBLE WE'RE ALL GONNA DIE tone in the LA Times piece.
— Dr. Angela Rasmussen (@angie_rasmussen) May 5, 2020
If you don't know what a single amino acid change even does, why is there an "urgent need for an early warning"? Warning about what? Are there any vaccines or drugs specifically targeting position 614 in spike? We don't even know if this has any kind of biological effect.
— Dr. Angela Rasmussen (@angie_rasmussen) May 5, 2020
These conclusions about increased transmissibility based on correlation analyses are an overreach. We don't know if the virus is "more transmissible." Experimental evidence or it didn't happen.
— Dr. Angela Rasmussen (@angie_rasmussen) May 5, 2020
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