Coronavirus: How worried should we be?

ในห้อง 'ทวีป เอเซีย' ตั้งกระทู้โดย supatorn, 27 มกราคม 2020.

  1. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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    Omicron’s Explosive Growth Is a Warning Sign
    We don’t know how severe Omicron is, but we do know it’s spreading very fast.
    By Sarah Zhang
    December 8, 2021
    A lot is still unknown around Omicron, but a worrying trend has become clear: This variant sure is spreading fast. In South Africa, the U.K., and Denmark—countries with the best variant surveillance and high immunity against COVID—Omicron cases are growing exponentially. The variant has outcompeted the already highly transmissible Delta in South Africa and may soon do the same elsewhere. According to preliminary estimates, every person with Omicron is infecting 3–3.5 others, which is roughly on par with how fast the coronavirus spread when it first went global in early 2020.
    In other words, Omicron is spreading in highly immune populations as quickly as the original virus did in populations with no immunity at all. If this holds and is left uncontrolled, a big Omicron wave lies ahead—bigger than we would have expected with Delta. Cases were already surging ahead of winter. The U.S. already had a too-low vaccination rate. And now Omicron threatens to eat away at the immunity we thought we had.

    To be clear, this does not mean the pandemic clock has reset to early 2020. Vaccines and previous infections can blunt the virus’s worst effects. Even if protection against infection is eroded, which experts expect, given Omicron’s heavily mutated spike protein, protection against severe disease and death should be more durable. Hospitalizations, rather than cases, might be a better measure of the virus’s impact, as I and others have argued. But if cases balloon dramatically, even a tiny percentage of patients becoming seriously ill can turn into too many hospitalizations all at once. Therein lies the danger possible with Omicron. “That small proportion of severe disease, if it’s multiplied by millions of cases, that will be bad,” says Jeffrey Barrett, the director of the COVID-19 Genomics Initiative at the Wellcome Sanger Institute. “I’m pretty worried.”
    This is the simple math we have to keep in mind: A tiny percent of a huge number is still a big number. A largely mild but uncontrolled Omicron wave could cause a lot of pain, hospitalizations, and death across a country.

    The ultimate impact of Omicron will depend on how tiny that tiny percent is and how huge that huge number is. We can’t say for sure, but we have some hints. Given the early trends out of South Africa, the U.K., and Denmark, a large Omicron wave is very possible, though not guaranteed. If we wanted to reassure ourselves, we could note that the absolute numbers of Omicron cases detected so far are so small, they may be skewed by chance, and we could be overestimating the variant’s growth by specifically searching for it. But Omicron is consistently increasing in the three countries looking hardest for it and therefore likely increasing quietly everywhere else.

    At the same time, Omicron doesn’t appear terribly virulent so far—but this observation comes with even bigger caveats. Doctors in South Africa, where Omicron is already dominant, have not seen as many severe cases as in previous waves. Other countries with small numbers of Omicron haven’t found many very sick patients either. But there are several reasons to believe that the news on severity could turn out less rosy than it currently appears. First of all, it’s early. Infections take weeks to progress to severe infections and eventually to death. Back in 2020, the first COVID case in the U.S. was confirmed on January 20, 2020; the first official COVID death was not reported until February 29. The picture may change with time.
     
  2. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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    (cont.)
    The early severity data are also confounded by who is getting sick. People who catch the virus early in a wave may be disproportionately young and healthy. “They’re probably taking fewer precautions than an elderly person or someone who’s immunocompromised,” says Vineet Menachery, a virologist at the University of Texas Medical Branch. South Africa’s population is itself fairly young, with a median age of 28, compared with the U.S.’s 38.5. And although vaccination rates are low in South Africa, where less than a quarter are fully inoculated, immunity from previous infection is very high, with one estimate suggesting 62 percent. A good number of Omicron cases are likely to be reinfections. Cases in people who are young or have been previously infected or both should be largely mild. If Omicron cases in this population were mostly severe, that would be a catastrophic sign. The fact that they’re not right now is merely a not-bad one.

    Scientists are now working furiously to understand Omicron’s effect on vaccinated people. Even if most breakthrough cases continue to be mild in the vaccinated, a small uptick in how many are not mild can still impact hospitalizations by the “tiny percent of a huge number” rule.

    Protection against infection after two doses is not looking very good. “Omicron was a huge jump in evolution,” says Jesse Bloom, an evolutionary virologist at the Fred Hutchinson Cancer Research Center, in Seattle. In what seems to be just a few months, the virus has changed as much as Bloom says he and many researchers expected it to change “over the span of four or five years.” In a slew of recent lab studies, the potency of antibodies that can neutralize the virus dropped anywhere from five- to sevenfold againstpseudoviruses” that have been engineered to carry Omicron’s spike mutations to 41-fold in a study with live Omicron viruses, which is the gold standard. (In the Beta and Delta variants, we saw drops of about six- and threefold compared with the original virus, respectively.) A 41-fold drop in neutralizing antibody activity after two doses does not mean a 41-fold drop in vaccine effectiveness. The real-world impact is hard to predict, but the effect is big enough that protection against infection might be quite low, says Florian Krammer, a virologist at Mount Sinai’s Icahn School of Medicine. “I think you’re dealing with a variant that has no problem infecting vaccinated individuals,” he says.

    Not all is lost, because protection against severe disease is likely to hold up much better against Omicron. The first glimmers of real-world data will probably come from the U.K., which is closely tracking Omicron’s spread. Protection against severe disease generally tends to be more durable because of how the immune system works. The first-line defenses of neutralizing antibodies might wane, but other, slower parts of the immune system, such as T cells, can still hold against severe disease. A booster can also strengthen the immune response, says Ali Ellebedy, an immunologist at Washington University in St. Louis. The preliminary data so far bear that out: Two doses plus infection or three doses get people to a higher baseline of neutralizing antibodies, which can better withstand the erosion from Omicron.

    Currently, however, fewer than half of Americans over 65 have gotten a booster shot, even though they were prioritized because the elderly tend to mount weaker vaccine responses. And 13 percent are still not fully vaccinated. The early glimpses of Omicron severity data cannot tell us how the variant affects an older and unvaccinated group, but everything about our experience so far with COVID suggests that there’s an extreme age skew to risk. Hospitalization trends this winter will likely track with how many older people remain unvaccinated. And the size of this group is another “small percent of a big number” problem: 13 percent of the 54 million Americans over the age of 65 translates to 7 million people at risk for requiring hospitalization if they get COVID. The unvaccinated population remains vulnerable to Omicron, as do immunocompromised people who don’t mount a good response to the vaccine. “Once you have spread, then you start bringing in all those populations that are inherently more susceptible, and that’s a problem,” Ellebedy says.
    Omicron is also arriving on the cusp of the holiday season, when Americans are gearing up for holiday parties and travel. “It’s an especially bad time for a new variant,” says Matthew Ferrari, who studies infectious-disease dynamics at Penn State. “People are already going to be hanging out. They already have plans. It’s going to be hard to disrupt those plans.” He points out that other seasonal respiratory illnesses such as the flu, which can also burden hospitals, are rising too. Nearly two years of pandemic have left many hospitals understaffed and backlogged. Health-care workers are quitting in droves. The level of tolerable COVID hospitalizations in a potential Omicron wave depends on the capacity of our health-care system to absorb them, and hospitals are already running with little slack.

    This “tiny percent of a huge number” problem has been with us since the very beginning of the pandemic. The coronavirus is much less deadly than other emerging viruses that have rung alarm bells in the past—SARS, MERS, or Ebola—but it is a whole lot more transmissible. Across the population, this still added up to so many severe cases, it overwhelmed our health-care system. COVID patients got worse care, as did anyone unlucky enough to get sick or injured during these big surges. We don’t want to get close to this point again.
    But we aren’t in the same position as in early 2020 because we now have the tools to control Omicron. And thanks to the scientists in South Africa who saw the risk of this variant very early, we have time to put them in place. Vaccines will likely keep protecting against severe infections, and a third shot is likely to boost that protection. Manufacturers are working on an Omicron-specific booster. We better understand the virus’s airborne transmission and how to stop it with masks and ventilation. We have antivirals on the horizon. We have rapid tests, though they should be easier to get. We know social distancing has curbed the virus before. Omicron is spreading fast, but we know how to slow it down.

    The Atlantic’s COVID-19 coverage is supported by grants from the Chan Zuckerberg Initiative and the Robert Wood Johnson Foundation.

    Sarah Zhang is a staff writer at The Atlantic.
    :- https://www.theatlantic.com/health/archive/2021/12/omicron-spread-infection-severity/620948/
     
  3. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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    You Are Going to Get COVID Again … And Again … And Again
    Will the danger mount each time, or will it fade away?
    By Katherine J. Wu
    May 27, 2022

    Two and a half years and billions of estimated infections into this pandemic, SARS-CoV-2’s visit has clearly turned into a permanent stay. Experts knew from early on that, for almost everyone, infection with this coronavirus would be inevitable. As James Hamblin memorably put it back in February 2020, “You’re Likely to Get the Coronavirus.” By this point, in fact, most Americans have. But now, as wave after wave continues to pummel the globe, a grimmer reality is playing out. You’re not just likely to get the coronavirus. You’re likely to get it again and again and again.
    “I personally know several individuals who have had COVID in almost every wave,” says Salim Abdool Karim, a clinical infectious-diseases epidemiologist and the director of the Center for the AIDS Program of Research in South Africa, which has experienced five meticulously tracked surges, and where just one-third of the population is vaccinated. Experts doubt that clip of reinfection—several times a year—will continue over the long term, given the continued ratcheting up of immunity and potential slowdown of variant emergence. But a more sluggish rate would still lead to lots of comeback cases. Aubree Gordon, an epidemiologist at the University of Michigan, told me that her best guess for the future has the virus infiltrating each of us, on average, every three years or so. “Barring some intervention that really changes the landscape,” she said, “we will all get SARS-CoV-2 multiple times in our life.”

    If Gordon is right about this thrice(ish)-per-decade pace, that would be on par with what we experience with flu viruses, which scientists estimate hit us about every two to five years, less often in adulthood. It also matches up well with the documented cadence of the four other coronaviruses that seasonally trouble humans, and cause common colds. Should SARS-CoV-2 joins this mix of microbes that irk us on an intermittent schedule, we might not have to worry much. The fact that colds, flus, and stomach bugs routinely reinfect hasn’t shredded the social fabric. “For large portions of the population, this is an inconvenience,” Paul Thomas, an immunologist at St. Jude Children’s Research Hospital, in Tennessee, told me. Perhaps, as several experts have posited since the pandemic’s early days, SARS-CoV-2 will just become the fifth cold-causing coronavirus.

    Or maybe not. This virus seems capable of tangling into just about every tissue in the body, affecting organs such as the heart, brain, liver, kidneys, and gut; it has already claimed the lives of millions, while saddling countless others with symptoms that can linger for months or years. Experts think the typical SARS-CoV-2 infection is likely to get less dangerous, as population immunity builds and broadens. But considering our current baseline, “less dangerous” could still be terrible—and it’s not clear exactly where we’re headed. When it comes to reinfection, we “just don’t know enough,” says Emily Landon, an infectious-disease physician at the University of Chicago.
     
  4. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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    (cont.)
    For now, every infection, and every subsequent reinfection, remains a toss of the dice. “Really, it’s a gamble,” says Ziyad Al-Aly, a clinical epidemiologist and long-COVID researcher at Washington University in St. Louis. Vaccination and infection-induced immunity may load the dice against landing on severe disease, but that danger will never go away completely, and scientists don’t yet know what happens to people who contract “mild” COVID over and over again. Bouts of illness may well be tempered over time, but multiple exposures could still re-up some of the same risks as before—or even synergize to exact a cumulative toll.

    “Will reinfection be really bad, or not a big deal? I think you could fall down on either side,” says Vineet Menachery, a coronavirologist at the University of Texas Medical Branch. “There’s still a lot of gray.
     
  5. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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    (cont.)
    The majority of infections we witnessed in the pandemic’s early chapters were, of course, first ones. The virus was hitting a brand-new species, which had few defenses to block it. But people have been racking up vaccine doses and infections for years now; immunity is growing on a population scale. Most of us are “no longer starting from scratch,” says Talia Swartz, an infectious-disease physician, virologist, and immunologist at Mount Sinai’s Icahn School of Medicine. Bodies, wised up to the virus’s quirks, can now react more quickly, clobbering it with sharper and speedier strikes.
     
  6. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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    (cont.)
    Future versions of SARS-CoV-2 could continue to shape-shift out of existing antibodies’ reach, as coronaviruses often do. But the body is flush with other fighters that are much tougher to bamboozle—among them, B cells and T cells that can quash a growing infection before it spirals out of control. Those protections tend to build iteratively, as people see pathogens or vaccines more often. People vaccinated three times over, for instance, seem especially well equipped to duke it out with all sorts of SARS-CoV-2 variants, including Omicron and its offshoots.

    Gordon, who is tracking large groups of people to study the risk of reinfection, is already starting to document promising patterns: Second infections and post-vaccination infections “are significantly less severe,” she told me, sometimes to the point where people don’t notice them at all. A third or fourth bout might be more muted still; the burden of individual diseases may be headed toward an asymptote of mildness that holds for many years. Gordon and Swartz are both hopeful that the slow accumulation of immunity will also slash people’s chances of developing long COVID. An initial round of vaccine doses seems to at least modestly trim the likelihood of coming down with the condition, and the risk may dwindle further as defenses continue to amass. (“We do need more data on that,” Gordon said.)
     
  7. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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    (cont.)
    Immunity, though, is neither binary nor permanent. Even if SARS-CoV-2’s assaults are blunted over time, there are no guarantees about the degree to which that happens, or how long it lasts. Maybe most future tussles with COVID will feel like nothing more than a shrimpy common cold. Or maybe they’ll end up like brutal flus. Wherever the average COVID case of the future lands, no two people’s experience of reinfection will be the same. Some may end up never getting sick again, at least not noticeably; others might find themselves falling ill much more frequently. A slew of factors could end up weighting the dice toward severe disease—among them, a person’s genetics, age, underlying medical conditions, health-care access, and frequency or magnitude of exposure to the virus. COVID redux could pose an especially big threat to people who are immunocompromised. And for everyone else, no amount of viral dampening can totally eliminate the chance, however small it may be, of getting very sick.

    Long COVID, too, might remain a possibility with every discrete bout of illness. Or maybe the effects of a slow-but-steady trickle of minor, fast-resolving infections would sum together, and bring about the condition. Every time the body’s defenses are engaged, it “takes a lot of energy, and causes tissue damage,” Thomas told me. Should that become a near-constant barrage, “that’s probably not great for you.” But Swartz said she worries far more about that happening with viruses that chronically infect people, such as HIV. Bodies are resilient, especially when they’re offered time to rest, and she doubts that reinfection with a typically ephemeral virus such as SARS-CoV-2 would cause mounting damage. “The cumulative effect is more likely to be protective than detrimental,” she said, because of the immunity that’s laid down each time.
     
  8. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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    (cont.)
    Al-Aly sees cause for worry either way. He is now running studies to track the long-term consequences of repeat encounters with the virus, and although the data are still emerging, he thinks that people who have caught the virus twice or thrice may be more likely to become long-haulers than those who have had it just once.

    There’s still a lot about SARS-CoV-2, and the body’s response to it, that researchers don’t fully understand. Some other microbes, when they reinvade us, can fire up the immune system in unhelpful ways, driving bad bouts of inflammation that burn through the body, or duping certain defensive molecules into aiding, rather than blocking, the virus’s siege. Researchers don’t think SARS-CoV-2 will do the same. But this pathogen is “much more formidable than even someone working on coronaviruses would have expected,” Menachery told me. It could still reveal some new, insidious qualities down the line.

    Studying reinfection isn’t easy: To home in on the phenomenon and its consequences, scientists have to monitor large groups of people over long periods of time, trying to catch as many viral invasions as possible, including asymptomatic ones that might not be picked up without very frequent testing. Seasonal encounters with pathogens other than SARS-CoV-2 don’t often worry us—but perhaps that’s because we’re still working to understand their toll. “Have we been underestimating long-term consequences from other repeat infections?” Thomas said. “The answer is probably, almost certainly, yes.”
    More to read-> https://www.theatlantic.com/health/...rch-immunity/639436/?utm_source=pocket-newtab
     
  9. supatorn

    supatorn ผู้สนับสนุนเว็บพลังจิต ผู้สนับสนุนพิเศษ

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