MeIf the Covid-19 epidemic in the United States had been a marathon, the country could have reached Mile 20. It has gone through a lot and there are already signs that things are improving. But leg cramps are increasing which can make that last push, which is not so short, really painful.
The two existing vaccines are reaching more people and, soon, the country probably have a third, from Johnson & Johnson, is just one dose and comes with easier transport and storage requirements. Cases and hospitalizations have plummeted since the peak last month, and now deaths – which are a slow indicator – have also declined. This will ease the burden on health systems and offer relief from what had been worsening infection and mortality data for months.
As the numbers go on the right direction, they are still at unimaginably high levels. Even in the best of days, more than 1,300 people die from Covid-19 in the United States, and much more than that die in many days, according to the Covid tracking project. The country has just registered less than 100,000 new infections confirmed in a single day, for the first time since the beginning of November; some days in January had more than 200,000 cases.
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Experts fear the decline is only temporary. One more transmissible – and, as the evidence increasingly suggests, one apparently more deadly – coronavirus shape called B.1.1.7 is starting to grow in the United States, even as the overall number of cases declines. It is unclear if the variant it may cause cases – and therefore hospitalizations and deaths – to increase again, but the specter of this is increasing the pressure to vaccinate as many people as quickly as possible and to decrease the number of cases in general.
“We continue to roll the dice and let the virus and its variants remain in the population at very high levels,” said Jason Salemi, an epidemiologist at the University of South Florida in Tampa.
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Salemi, a native of Tampa, was speaking on Monday morning, the day after the Buccaneers won the Super Bowl in their hometown. He knew that many people were celebrating, and he knew that people would travel to the city for the game and return 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 warned that variant counts were heavily influenced by how much genomic surveillance a state conducted, 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 time, knowing what may be coming, it is bittersweet, ”he said.
The cases do not increase or decrease for any reason; infection trends are driven by policies, individual behavior, the virus itself and its environment. And experts point out a number of human factors for the current decline in infections: We are probably past any increase in transmission that the vacation has caused. As cases increased at the end of last year, more states and communities imposed stricter restrictions on business and meetings. People who have seen their local hospitals flooded by patients may have started to be more cautious on their own.
“In California, I think people were getting the message that the state was not doing well,” said Karin Michels, UCLA’s head of epidemiology, in a city where the load placed in hospitals was so intense there were fights getting enough oxygen for patients. “They were waking up and I think they were scared. We had our time in New York, so I think people are more careful and more aware than before. “
The number of daily Covid-19 tests has also started to drop somewhat, in part because local health departments are shifting attention away from vaccine campaigns. But experts say the test numbers have not dropped enough to justify the total drop in confirmed cases; in addition, other metrics like hospitalizations and deaths are also falling.
Other potential factors for the decline in cases include the seasonality of the virus and immunity at the population level.
We tend to think of the cold and flu season as a period of about five months, a period when the cold, dry climate allows respiratory viruses to spread more easily and when we are taken home. But, depending on the pathogen, that comprehensive period of time is made up of a series of more compact spikes in viral spread. “It is possible that, for certain viruses, they have a shorter period of time,” when they are at the peak of prevalence, said Matthew Binnicker, director of clinical virology at the Mayo Clinic.
For the four coronaviruses that cause common colds, for example, their cumulative period of maximum activity can last for the entire season, but “if you look at each individual strain, you’ll see that each of them is maybe two, three months old,” said the epidemiologist Michael Mina, from the Harvard School of Public Health TH Chan. Although SARS-CoV-2, the coronavirus that causes Covid-19, has shown that it can spread at any time – remember the summer outbreaks in the South – it is possible that the country is coming out of its peak period.
Many experts hope that the more people are vaccinated, this will help limit transmission. But so far, about 10 million people in the United States have received both doses of their vaccines (the two immunizations authorized so far require two doses).
However, there were more than 26 million people who confirmed Covid-19, a number that suggests that the true number may, by some estimates, be in the range of 100 million to 125 million, if not more. Most of these people probably have some immune protection, so even though collective immunity has not been achieved, the virus still has a harder time finding new people to infect.
“We are well on our way towards the herd’s immunity limits,” said Mina. “And, like anything, it’s a continuum, so we begin to feel the benefits of it the closer we get.”
The drop in cases is also evident at the local level. At the University of Alabama at Birmingham, there are about 175 patients hospitalized with Covid-19, since the peaks in December and January and back to numbers before Thanksgiving, said Rachael Lee, an infectious doctor. But when the hospital started serving Covid-19 in the spring, it had about 30 patients. “We are still incredibly tall,” said Lee.
If the falling cases are like the floodwaters receding, the accelerated build-up of B.1.1.7 could be like a congregation of crocodiles accumulating below the surface. The variant could become dominant in the US as early as next month, and its snowball comes like a snowball while leaders are easing restrictions due to conditions for improvement at the moment. California lifted up their home stay requests located, New York is opening indoor restaurants this week, and Iowa has finished his mask mandate and restrictions on meetings.
But ask experts how B.1.1.7 can reshape the U.S. epidemic and you will hear “it depends” or “it is the wildcard”, although there is a sense of calm before the storm. Having so much population immunity and making vaccines reach more people could lessen its impact – perhaps the variant just slows down cases – but data from other countries indicate that severe measures must be taken to control it and contain outbreaks. Most places in the United States do not seem inclined to impose such restrictions.
There are other worrying variants too, called P.1 and B.1.351. They were first seen in Brazil and South Africa, respectively, but already since it was identified in small numbers in the United States. Studies have shown that mutations in the variants threaten the power of some vaccines, and in clinical trials, some vaccines performed worse against B.1.351 than against other forms of the coronavirus.
Scientists are still trying to find out what helps P.1 and B.1.351 to overcome other variants. They could be more transmissible like B.1.1.7, but while B.1.1.7 took off in several countries, so far, great peaks in P.1 and B.1.351 have only been seen in the countries where each of them emerged.
What may also be happening, said infectious disease expert Kristian Andersen of the Scripps Research Institute, is that the variants, which share some mutations, are only better for reinfecting people who have already had a Covid-19 case.
Brazil and South Africa had major outbreaks at the beginning of the pandemic, so there must be some decently high level of population immunity in these countries. Laboratory experiments have shown that the variants can partially evade the immune response generated after an infection, so it is possible that the two strains are able to circulate among people who have already been infected. Other types of viruses may not be able to do this – they are blocked by existing immunity – and the result is that P.1 and B.1.351 increase in prevalence while other variants are reduced.
Even if P.1. and B.1.351 are only 20% to 30% better at re-infecting people than other variants, Andersen said, because dissemination “is an exponential process, which will surpass others very quickly”.