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IIf the US Covid-19 epidemic were a marathon, the country might have hit Mile 20. It’s been through a lot, and already there are signs that things are improving. But there are leg cramps that could make this last push, which is actually not that short, really painful.
The two existing vaccines reach more people, and soon the country will probably have a third, from Johnson & Johnson, it’s just a dose and comes with easier transport and storage requirements. Cases and hospitalizations have dropped steeply from their highs last month, and now deaths – which is a lagging indicator – have also fallen. This will ease the burden on health systems and provide respite from what for months has worsened data on infections and deaths.
While the numbers come in the right waythey are still both incredibly high levels. Even on the best days, more than 1,300 people die from Covid-19 in the United States, and many more die on multiple days, according to the Covid monitoring project. The country has recorded less than 100,000 new confirmed infections in a single day for the first time since early November; on some days in January there were over 200,000 cases.
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Experts fear the decline is temporary. A more transmissible – and, as evidence increasingly suggests, a seemingly more deadly – form of coronavirus called B.1.1.7 is starting to develop in the United States, although the overall number of cases is declining. It’s not clear if the variant could lead to a further increase in cases – and therefore hospitalizations and deaths – but the specter is additional pressure to vaccinate as many people as quickly as possible and reduce overall cases as much as possible.
“We continue to roll the dice and let the virus and its variants stay in the population at fairly high levels,” said Jason Salemi, an epidemiologist at the University of South Florida in Tampa.
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Salemi, from Tampa, was speaking Monday morning, the day after the Buccaneers’ Super Bowl victory in their hometown. He knew that a lot of people were celebrating outside, and knew that people were going to town for the game and going home. Cases and hospitalizations in the state have declined in recent weeks, but Florida also has the most confirmed cases of B.1.1.7 of any state.
Salemi cautioned that the number of variants was greatly influenced by the degree of state-led genomic surveillance and that Florida is the third most populous state, so it would normally have more cases than most places. Still, “I was so excited that we won [the Super Bowl], but all the while, knowing what might happen, it’s bittersweet, ”he says.
Cases do not increase or decrease for just one reason; infection trends are dictated by policies, individual behavior, the virus itself and its environment. And experts point to a number of human factors behind the current decline in infections: We are probably past the transmission bump caused by the holidays. As cases escalated at the end of last year, more states and communities placed tighter restrictions on businesses and gatherings. People who have seen their local hospitals inundated with patients may have started to be more careful on their own.
“In California, I think people were getting the message that the state was not doing well,” said Karin Michels, president of epidemiology at UCLA, in a town where the the burden on hospitals was so intense there were struggles get enough oxygen for patients. “They were waking up and I think they were scared. We had our moment in New York, so I think people are more careful and more aware than they were before.
The number of daily Covid-19 tests has also started to drop a bit, in part because local health services are shifting their attention to vaccination campaigns. But experts say test numbers aren’t low enough to account for the total drop in confirmed cases; In addition, other parameters such as hospitalizations and deaths are also declining.
Other potential factors for the decline in cases include the seasonality of the virus and population-level immunity.
We tend to think of cold and flu season as about five months, a time when cold, dry weather allows respiratory viruses to spread more easily and when we are led indoors. But depending on the pathogen, this overall time period is made up of a series of more compact peaks of viral spread. “It is possible that for some viruses, they have a shorter period of time” when they reach a peak in prevalence, said Matthew Binnicker, director of clinical virology at the Mayo Clinic.
For the four coronaviruses that cause the common cold, for example, their cumulative period of peak activity may last the entire season, but “if you look at each individual strain, you see that they are each maybe two, three months old,” said the epidemiologist. Michael Mina of the TH Chan School of Public Health at Harvard. Although SARS-CoV-2, the coronavirus that causes Covid-19, has shown that it can spread at any time – think of the summer epidemics in the South – it is possible that the country is coming out of its peak period.
Many experts expect more people to get vaccinated, which will help limit transmission. But so far, about 10 million people in the United States have received both doses of their vaccines (the two vaccinations allowed so far both require two doses).
However, there have been over 26 million people who have confirmed Covid-19, a figure which suggests that the true figure could be, by some estimates, between 100 and 125 million, if not more. Most of these people probably have some immune protection, so even if herd immunity has not been achieved, the virus has an even harder time finding new people to infect.
“We are well on our way to the herd immunity thresholds,” Mina said. “And like everything, it’s a continuum, so we’re starting to feel the benefits as we get closer.”
The decline in cases is also evident at the local level. At the University of Alabama at Birmingham, there are around 175 patients hospitalized for Covid-19, down from peaks in December and January and pre-Thanksgiving figures, said Rachael Lee, a medical specialist. infectious. But when the hospital started seeing Covid-19 in the spring, it had around 30 patients. “We’re still incredibly high,” Lee said.
If the descending cases are like receding flood waters, the accelerated build-up of B.1.1.7 could be like a congregation of alligators amassing below the surface. The variant could become dominant in the United States as early as next month, and its snowballing comes as leaders relax restrictions due to improving conditions right now. California survey its stay-at-home orders located, New York City is opening an indoor restaurant this week and Iowa has completed his mask mandate and restrictions on gatherings.
But ask the experts how B.1.1.7 could reshape the US epidemic and you’ll hear “it depends” or “it’s the wild card,” although there is a sense of calm before the storm. Having so much population immunity and getting vaccines to reach more people could mitigate its impact – perhaps the variant only slows the decline in cases – but data from other countries indicates action severe should be taken to control it and stop epidemics. Most places in the United States did not seem inclined to impose these types of restrictions.
There are also other worrisome variants called P.1 and B.1.351. They were first seen in Brazil and South Africa, respectively, but have since been identified in small numbers in the United States Studies have shown that mutations in the variants threaten the potency of some vaccines, and in clinical trials, some vaccines performed less well against B.1.351 than against other forms of coronavirus.
Scientists are still trying to figure out what helps P.1 and B.1.351 outperform other variants. They might be more transmissible like B.1.1.7, but while B.1.1.7 has taken off in several countries, so far huge peaks in P.1 and B.1.351 have only been seen in the countries where they each emerged. .
What could also happen, said infectious disease expert Kristian Andersen of the Scripps Research Institute, is that the variants, which share certain mutations, are simply better at re-infecting people who already had a case of Covid- 19.
Brazil and South Africa both experienced major outbreaks at the start of the pandemic, so the level of population immunity is expected to be decently high in those countries. Laboratory experiments have shown that the variants can partially evade the immune response generated after infection, so it is possible that both strains can circulate to some extent among people who are already infected. Other types of viruses might not be able to do this – they are blocked by existing immunity – and the result is that the prevalence of P.1 and B.1.351 increases while other variants are reduced.
Even if P.1. and B.1.351 are only 20% to 30% more effective at re-infecting people than the other variants, Andersen said, because the spread “is an exponential process, it will overtake others very quickly.”
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