Public health officials in the United Kingdom announced over the weekend that there is evidence that a mutation of the coronavirus in the country has made it as much as 70 percent more transmissible. As a result, Prime Minister Boris Johnson imposed the country’s most stringent restrictions since March in the London area. Canada, Israel, Iran, Colombia, Morocco, and countries in the European Union have put a hold on flights from the U.K. in an attempt to stem the spread of this new variant. In order to get a better sense for what this means for the U.S., I spoke to Angela Rasmussen, a virologist with the Center for Global Health Science and Security at Georgetown University.
Aaron Mak: What do we know, and what do we still need to figure out?
We don’t know most of the things that have come up about this new variant. We don’t actually know that it in fact is more transmissible. That has been based on epidemiological evidence: It has become much more prevalent in Southeastern England and parts of London much more quickly than we would expect. Also, there are some reports—although the more granular data isn’t out—saying that viral loads are higher in people who are diagnosed with COVID who have this variant. Based on those two pieces of data, that’s why people are speculating that this is more transmissible, but that’s not proven. My inclination is to think that it probably does have some kind of transmission advantage, but we need to make sure that that actually is true, and that it can’t be explained by other things such as people maybe changing their behavior, not wearing masks as much, getting together in larger groups.
What kind of experimental data would we need to determine whether it is actually more transmissible, and around when could we find that out?
People are definitely already starting to do those types of experiments and to show that the mutations that this variant has give some kind of fitness advantage, or make the virus better at replicating. People will do studies in cell culture; they will look at the ability of the spike protein specifically to enter cells. They’ll also look at growth curves to see how well this variant can grow relative to other variants. And then they will put it into animals and see if the animals are shedding more virus, if they are able to transmit it to other naive animals more efficiently, if the virus causes any difference in terms of the disease manifestations after infection. It takes several days to actually do the experiment itself, it can take some more days to look at exposure experiments, and it can take more time after that to actually titrate the virus and look at the tissue pathology and all of those things. I think we’re weeks away from getting some of that information that would really conclusively show that there’s a difference in the transmissibility of this virus.
Viruses mutate all the time, and thousands of coronavirus mutations have been documented already. Why is this one getting so much attention?
Because it became so prevalent so quickly. This has really occurred over a couple months, which is pretty fast. Earlier on in the pandemic, there was this other mutation [called] D614G in the spike protein, which was said to be more transmissible. After a lot of experimental work, it looks like it does have some fitness advantages and it may be transmitted more quickly, at least in an experimental hamster model. But it’s really hard to say that that’s making a difference in the real world, and it took months really for D614G to become the dominant circulating form of the virus in the U.S. This [new variant] has over a much shorter period of time. And D614G is one mutation; this variant has 17 mutations in it.
What does this mean for efforts to use vaccines to combat the pandemic?
They can take serum from people who have been vaccinated and see whether that serum and the antibodies within it can neutralize the variant. … If this variant is not effectively targeted by antibodies that are elicited by the vaccines that are being rolled out now, that means we’ll have to change the vaccine. The good news is the mRNA vaccines that have been given Emergency Use Authorization are very easy to change. It would delay rollout to the general population of these vaccines, but we’re getting ahead of ourselves starting to worry about that now. We definitely need to keep an eye on this, but we don’t even know that this variant is circulating in the U.S.
On Sunday, New York Gov. Andrew Cuomo called on the federal government to consider banning flights from the U.K. and also suggested that the new variant is likely already in the U.S. Does that seem premature?
That seems too late. It sounds “post-mature.” I think there’s a very good chance that this variant is already here. If it is, then what is shutting down flights from the U.K. going to do to fix that? The other issue is larger. It really irritates me when people with Gov. Cuomo’s platform call for huge policy decisions like that based on very little evidence. Right now, the larger problem is—whether we have this variant circulating in the U.S. or not—we have out-of-control transmission throughout the entire country. Blocking flights from anywhere is not going to do anything to address that.
In terms of this variant, of course we need to study it. I’m especially concerned with what would happen if a virus with increased transmissibility gets into the situation that we’re already in. Would that be enough to push our health care system, which has already strained, past its breaking point? That gets to the heart of the problem. We have out-of-control transmission. We need to address that here. There’s plenty of transmission occurring right now with the variants that we do know are circulating in the U.S.
What should the general public in the U.S. do with this new information? Is there anything we should be doing differently at this point?
No. I think the thing that we should be doing differently, though, is communicating to people that even if this is more transmissible, what we really need to worry about right now is transmission in general. It would be a disaster on top of a disaster if this is more transmissible and it starts circulating here, or if it already is, and people get together for, say, Christmas.
What people should understand is that mutation does not confer magical powers to viruses. This virus might be more transmissible, but that doesn’t mean that it’s more airborne. It doesn’t mean that it’s going to start causing entirely new forms of the disease. It doesn’t mean that it’s going to be transmitted via different routes or that it’s somehow evolved the ability to get around masks. The same precautions for this variance apply as to every other variant of SARS-CoV-2. People should wait to see definitely if it’s something to be concerned about, but it’s not something to panic over. We already know what to do to reduce our exposure risk. I just, again, implore people to do that.
from Slate Magazine https://ift.tt/2KtZKui
via IFTTT
沒有留言:
張貼留言