Why Are the New COVID-19 Strains Spreading More Quickly?
Research suggests the new COVID variants that were first detected in the UK and South Africa are more contagious than previous strains of the virus. Here are some theories as to why.
Among record numbers of new COVID-19 cases and deaths across the U.S., there's been some hopeful news: Nearly 9 million people (and counting) in the country have received the first dose of the COVID-19 vaccine. (ICYMI: How Effective Is the COVID-19 Vaccine?)
But, there's a bit of a curveball. A new, more infectious strain of SARS-CoV-2 (the virus that causes COVID-19), called B.1.1.7, is spreading rapidly. Commonly referred to as the UK variant of the virus (given that it was first detected in that area), B.1.1.7 has now been spotted in several countries around the world and multiple states in the U.S., including California, Colorado, Connecticut, Florida, Georgia, New York, Pennsylvania, and Texas, according to data from the Centers for Disease Control and Prevention (CDC).
Anthony Fauci, M.D., the director of the National Institute of Allergy and Infectious Diseases, recently told Newsweek that he suspects that B.1.1.7 is in even more areas of the U.S. — and that it will continue to spread. Dr. Fauci also said that the UK variant "clearly is impacting the function of the virus" by allowing it to spread more easily between people, a factor U.S. public health officials are watching very closely.
"We take that very seriously because if you have greater transmissibility, you will get more cases," Dr. Fauci told Newsweek. "When you get more cases, you get more hospitalizations. And when you get more hospitalizations, you ultimately wind up getting more deaths." (More here: What's the Deal with the New Strain of COVID-19 from the UK?)
Meanwhile, experts are also tracking two separate COVID-19 variants detected in South Africa (501Y.V2) and Brazil (P.1), respectively. So far, health officials in Zambia, Finland, the UK, Australia, Switzerland, Japan, and South Korea have found the South African variant in their lab testing, according to the World Health Organization (WHO). As for the strain associated with Brazil, Japan's National Institute of Infectious Diseases (NIID) said it detected the variant in four travelers from the South American country in early January and is continuing to investigate how contagious the strain might be.
Echoing his thoughts on the UK variant, Dr. Fauci told Newsweek that he'd be "surprised" if the South African variant wasn't already in the U.S. (though no case has officially been reported), considering how quickly it's spread thus far. In fact, some experts are warning that 501Y.V2 may be even more contagious than the UK strain.
It's a lot to digest, but, deep breaths. Here's what you need to know about these new COVID variants, plus why they're thought to be more infectious than "regular" COVID-19.
First, why do viruses mutate in general?
All viruses mutate. It happens as a virus replicates — something the virus needs to do to survive. "Viruses multiply billions of times, so many small mutations occur," explains William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine. "The vast majority of these mutations are harmless, useless, and sometimes even detrimental to the virus so they don't go anywhere."
But sometimes mutations can make a virus stronger — and that seems to be the case with these new COVID variations. "In the instance of the UK and South African variants, a series of mutations took place that has made these viruses more contagious," says Dr. Schaffner.
Why are the new COVID-19 strains more contagious?
B.1.1.7 (the UK strain) has several mutations in its genome (aka genetic makeup), some of which are in the virus's spike protein, an area that the virus uses to bind to receptors in your cells to infect you with COVID-19, explains infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. "One series of mutations, in particular, seems to make the virus able to bind to your cells in a more efficient manner," he says.
The CDC explains it this way: The B.1.1.7 variant has a mutation in the receptor-binding domain of the spike protein. That mutation causes an amino acid called asparagine — which is normally present in the "regular" SARS-CoV-2 virus — to be replaced with a different amino acid called tyrosine.
That's a little technical but, essentially, this amino-acid swap makes the virus's spike protein stronger and, as a result, appears to improve the virus's ability to infiltrate someone's cells and infect them with COVID-19.
Both 501Y.V2 (the COVID-19 variant that was first spotted in South Africa) and P.1 (the strain first detected in Brazil) similarly have multiple mutations in the spike protein that seem to allow the virus to spread more readily and infect human cells, according to the CDC. "The more viruses can get into cells more quickly, the more the virus replicates and the more it sheds, potentially infecting others," explains Dr. Schaffner.
As of now, experts estimate that a person infected with the COVID variant from the UK may spread the virus to, on average, 1.5 people, while someone with the "standard" COVID strain may pass the virus to about 1.1 people, said Maria Van Kerkhove, a technical lead at the WHO, according to U.S. News & World Report. Researchers are still studying just how quickly the COVID strains from South Africa and Brazil can spread compared to previous variants.
But Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo in New York, says it's important to note that, at this point, the data does not definitively say that B.1.1.7 (or 501Y.V2, for that matter) is more contagious.
"B.1.1.7 is believed to be more infectious because it was first recognized in the UK at the end of September and, by December, the proportion of cases of COVID-19 due to this strain had significantly increased," explains Dr. Russo. "That suggests the new strain was outcompeting the current strain and was, therefore, more infectious."
While Dr. Russo says it's "likely the case" that the genetic makeup of these new COVID variants does make them more contagious, he also points out the possibility that a phenomenon called the "founder effect" could be playing a role in the spread. In other words, it may be the case that someone who was infected with B.1.1.7 became a superspreader in the UK (i.e. perhaps they weren't social distancing or wearing a mask in public), and the strain became more widespread from there, he explains. The same theory might explain the spread of the 501Y.V2 and P.1 variants that were first found in South Africa and Brazil, respectively, but more data is needed to be certain.
So, while Dr. Russo says these new strains are "likely more infectious," it's not a "slam dunk" of a conclusion just yet.
Are the new COVID-19 strains more deadly?
On the bright side, there are currently no data to suggest that these variants could be more deadly or dangerous than the existing dominant strain of SARS-CoV-2, says Dr. Schaffner. "It's just more spreadable, more contagious," he adds. (Related: Everything You Need to Know About Coronavirus Transmission)
But there could be an indirect effect here. "The more contagious it is, the more widely it will spread, the more people will become infected, the more people with underlying health conditions will get it, and the more people will die," explains Dr. Schaffner. "But not because the virus is more virulent."
What does this mean for COVID-19 vaccines?
Right now, it appears that both the Pfizer-BioNTech and Moderna vaccines — the first vaccines to receive emergency use authorization (EUA) from the FDA — are still effective in protecting the body from a COVID-19 infection involving either of these new mutations.
Still, considering how quickly these variants have developed (and spread), you might be wondering if the COVID-19 vaccine will eventually become an annual injection that needs to be updated each year to account for these new mutations, similar to the flu vaccine. Dr. Adalja says that's unlikely at this point. (Related: Everything You Need to Know About COVID-19 Vaccine Side Effects)
At some point in the future, there could be a "need for an update" to one or more of the COVID-19 vaccines, says Dr. Adalja. But he doesn't anticipate it being at the level of annual flu vaccination. (Related: Can the Flu Shot Protect You from Coronavirus?)
Overall, Dr. Schaffner recommends taking a slow, socially-distanced breath, and following the COVID-19 precautions you've memorized by this point. "Wearing masks and social distancing becomes even more important now that these strains are around," he says. "They will help protect against these new strains as well as the standard strains."
The information in this story is accurate as of press time. As updates about coronavirus COVID-19 continue to evolve, it’s possible that some information and recommendations in this story have changed since initial publication. We encourage you to check in regularly with resources such as the CDC, the WHO, and your local public health department for the most up-to-date data and recommendations.