Hospitalizations for Covid-19 in the United States are dropping after reaching record levels this month – a welcome sign that the winter wave may finally be stabilizing. But as potentially more contagious variants of the virus circulate, coronavirus modelers warn that the United States is not yet out of danger.
The emergence of new variants is not at all surprising, but experts say that without a better understanding of how these strains affect things like the transmissibility and effectiveness of existing vaccines, it is difficult to know how the pandemic can develop.
“There is so much in the air, and the new variants have played a big wrench in our ability to model things,” said Dr. Jeanne Marrazzo, professor of medicine and director of the infectious diseases division at the University of Alabama at Birmingham. “All of these things make the crystal ball very cloudy.”
Although hospitalizations and the number of new infections in the U.S. have decreased compared to the previous seven days, deaths from Covid-19 are still increasing. The country surpassed 400,000 deaths this week and on Wednesday set a daily record, with 4,131 reported deaths, according to an NBC News count.
The coronavirus is estimated to have undergone thousands of mutations since it was detected in humans. Many turned out to be inconsequential, but scientists are concerned about any changes that could make the virus more contagious or make available vaccines less effective.
Evidence from the UK has shown that one of these variants, known as B.1.1.7, spreads more easily from person to person, although it does not appear to make people sicker and appears to be susceptible to vaccines. A report released last week by the Centers for Disease Control and Prevention said the UK variant could become the dominant strain in the United States in March.
New variants have also been reported in South Africa, Brazil and the United States, with a flurry of research underway to characterize the changes. Early laboratory experiments suggest that vaccines made by Pfizer and BioNTech and Moderna may be less effective against the variant identified in South Africa, but the research has not been done on humans and the findings have yet to be reviewed by peers.
As variants emerge, it will be crucial to adhere to measures to slow the spread of the virus and accelerate the rate of vaccinations to prevent all of these numbers from increasing, said coronavirus modeler Alessandro Vespignani, director of the Network Science Institute at Northeastern University.
This is because a more contagious variant is likely to result in more cases overall, which further increases the pressure on health systems that are already overburdened.
“It is a kind of race against the emergence of new strains that are more transmissible,” said Vespignani. “If we launch the vaccine fast enough and keep the epidemic levels low, it will also decrease the variants and give us more time.”
The distribution of vaccines has been problematic, with some states running out of supplies, while others have difficulty administering all the doses they were receiving.
And there are concerns that the United States is not doing enough to track genetic changes in the virus by sequencing genetic codes. Not knowing specifically which variants are present in the country makes it more difficult to protect those at risk, said former CDC official Ali Mokdad, professor of global health at the University of Washington. It also makes it more challenging for modelers to design how the pandemic can unfold.
“If we don’t keep up with what’s going on, we may have a homemade variant that is more transmissible than what we saw in the UK, and we wouldn’t know,” he said.
Mokdad is part of the University of Washington Institute of Health Metrics and Assessment, which developed one of the most cited coronavirus models. Its current projection shows that, although the number of new infections is decreasing in the United States, deaths from Covid-19 are not expected to peak until early March.
Still, Mokdad said, there are ways for the United States to avoid additional spikes in hospitalizations and deaths, even as new variants appear.
“We have to do what we know to be effective – distance yourself socially and wear a mask,” he said. “We cannot celebrate prematurely, because if everyone assumes that the worst is over, we will see the peaks again.”
And while the models predict that deaths will continue to rise for a few more weeks, it is possible to level the curve if people remain vigilant, said Vespignani.
“Each prediction is not a deterministic outcome,” he said. “We can do something to change the trajectory.”
