2020-05-04 nap bejegyzései

(3180) Mi lehet a pandémia vége

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How the COVID-19 Pandemic Could End

We know how the COVID-19 pandemic began: Bats near Wuhan, China, hold a mix of coronavirus strains, and sometime last fall one of the strains, opportunistic enough to cross species lines, left its host or hosts and ended up in a person. Then it was on the loose.

What no one knows yet is how the pandemic will end. This coronavirus is unprecedented in the combination of its easy transmissibility, a range of symptoms going from none at all to deadly, and the extent that it has disrupted the world. A highly susceptible population led to near exponential growth in cases. “This is a distinct and very new situation,” says epidemiologist and evolutionary biologist Sarah Cobey of the University of Chicago.

But past pandemics do offer hints of the future. While there is no one historical example to follow, humanity has gone through several large epidemics in the past 100 or so years that eventually stopped ravaging society. The ways they came to a halt offer guidance to a world looking for ways to restore health and some sense of normalcy. Three of those experiences, Cobey and other experts say, suggest that what happens next depends on both the evolution of the pathogen and of the human response to it, both biological and social.

 

The Current End Game

Projections about how COVID-19 will play out are speculative, but the end game will most likely involve a mix of everything that checked past pandemics: Continued social-control measures to buy time, new antiviral medications to ease symptoms, and a vaccine. The exact formula—how long control measures such as social distancing must stay in place, for instance—depends in large part on how strictly people obey restrictions and how effectively governments respond. For example, containment measures that worked for COVID-19 in places such as Hong Kong and South Korea came far too late in Europe and the U.S. “The question of how the pandemic plays out is at least 50 percent social and political,” Cobey says.

The other 50 percent will probably come from science. Researchers have banded together like never before and are working on multiple fronts to develop remedies. If any of the several antiviral medications currently in development prove effective, they will improve treatment options and lower the numbers who get seriously ill or die. A technique to screen for SARS-CoV-2 neutralizing antibodies, an indicator of immunity in recovered patients, could also prove very useful. Krammer and his colleagues have developed one such test, and there are others. Previously used only in local epidemics, these new serological assays won’t end the pandemic, but they could make it possible  to spot and use antibody-rich blood as a treatment for critically ill patients; more certainly, the tests will also get people back to work faster if those who fought off the virus and are immune can be identified.

It will take a vaccine to stop transmission. That will take time—probably a year from now. Still, there is reason to think a vaccine could work effectively. Compared with flu viruses, coronaviruses don’t have as many ways to interact with host cells. “If that interaction goes away, [the virus] can’t replicate anymore,” Krammer says. “That’s the advantage we have here.” It is not clear whether a vaccine will confer long-term immunity as with measles or short-term immunity as with flu shots. But “any vaccine at all would be helpful at this point,” says epidemiologist Aubree Gordon of the University of Michigan.

Unless a vaccine is administered to all of the world’s eight billion inhabitants who are not currently sick or recovered, COVID-19 is likely to become endemic. It will circulate and make people sick seasonally—sometimes very sick. But if the virus stays in the human population long enough, it will start to infect children when they are young. Those cases are typically, though not always, quite mild, and so far the children appear less likely to develop severe disease if they get reinfected as adults. The combination of vaccination and natural immunity will protect many of us. The coronavirus, like most viruses, will live on—but not as a planetary plague.

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