Why Are the New Strains of COVID-19 More Contagious? Here's What We Know So Far
One of the new strains is already infecting people in the US. Here's what we know so far.
Just when things were starting to look up on the pandemic front, with a rollout of vaccines underway across the US and in several other countries, the latest news about COVID-19 has reminded us that we've still got a long way to go. A more infectious strain of the virus, identified first in the UK and known as B.1.1.7, has been confirmed in at least 33 countries and five states (California, Colorado, Florida, New York, and Georgia).
Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, said it's likely that the B.1.1.7 strain has already spread to other states. "I think it's pretty clear that if it's in places like California, and New York and Colorado… that pretty soon it's going to be in several more states," Dr. Fauci told Newsweek in a January 6 article.
Meanwhile, another newly identified strain, linked to a surge in COVID-19 cases in South Africa, is believed to also be more infectious than previous strains. This new second strain, named 501.V2, hasn't been confirmed yet in the US, but Dr. Fauci told Newsweek on January 5 that he believes it's already here. The 501.V2 strain has also been found in the UK, France, Finland, Zambia, Switzerland, Japan, and South Korea, per Newsweek.
Right now, experts do not believe the UK and South African COVID-19 strains are making people sicker or are more deadly, and it's not clear if they will impact the effectiveness of the new vaccines. Here's what experts are saying about the UK-evolved variant that's currently infecting Americans, why potentially dangerous viral strains evolve in the first place, and what this means when it comes to staying safe.
Why are the new strains more contagious?
First, keep in mind that any microorganism (like a virus or bacteria) can mutate, and there can be no replication without the chance occurrence of such errors, Charles Bailey, MD, medical director for infection prevention at Providence St. Joseph Hospital and Providence Mission Hospital in Orange County, California, tells Health. The more a virus replicates, the more it mutates.
"A mutation is a change in the viral RNA, which may cause a change in the structural proteins of the virus," Supriya Narasimhan, MD, chief of infectious diseases at Santa Clara Valley Medical Center in San Jose, California, tells Health. Viruses mutate because they're carried by different host cells, she says. Being exposed to vaccines also puts pressure on the virus to adapt in order to survive. (Basically, they're trying to stay one step ahead of our efforts to kill them.) But not all mutations are meaningful—some may have no effect on the fitness of infectivity of the virus, while others may actually be detrimental to the virus.
The B.1.1.7 strain may enter host cells more easily, causing infection
Occasionally, however, a mutation emerges that gives the new virus an advantage over the original version—such as the ability to escape detection, greater infectivity, or less susceptibility to vaccine, Dr. Narasimhan explains. B.1.1.7 falls into that category. This variant has 17 mutations in its genome, some of which are in the Spike protein, which is what the virus uses to bind to receptors in human cells.
A mutation to the spike protein may theoretically allow the new strain to more easily enter host cells, thereby triggering infection. "Some estimates have calculated an approximately 50% increase in infection," Dr. Bailey explains. "in other words, 15 new infections from the mutated strain versus 10 from the current COVID-19 strain."
One such mutation is N501Y, which is in the receptor binding domain (RBD) of the Spike protein of the virus. Scientists believe that this mutation may cause it to bind more tightly to the human angiotensin-converting enzyme 2 (ACE2) receptor. Other changes in the Spike protein may allow this mutation to evade detection by certain PCR (polymerase chain reaction) methods, Dr. Narashimhan adds. "It is postulated that the combination of the tighter binding and, perhaps, the failure of some test methods, make it more contagious," she says.
The more contagious strains aren't making people sicker
Dr. Narasimhan confirms that more severe illness hasn't been seen with the new variant. But she points out that if more people get infected, it follows that more will get sick and need hospital care—and a subset of those will not survive. Even if the new variant is not more lethal, the fact that it can spread faster and more effectively may translate to a higher death and disability toll. "To put it another way, a small percentage of a very big number can easily be much, much bigger than a big percentage of a small number," she says. "This is one of the main reasons we are concerned."
The B.1.1.7 strain also seems to have spread farther than experts initially thought—even before it had been identified as a new variant. "This also happened in early 2020 when the virus was well inside the US and beyond China even before we knew it," Dr. Narasimhan says.
Speed of spread doesn't just increase infection numbers; it can also decrease the effectiveness of contact tracing. "The faster any virus spreads, the more people may have been infected by the time an infected individual is first identified, and attempts to contain its spread through separation of susceptible family members or contact tracing can even begin," Dr. Bailey explains.
Here's what to do to lower your risk
Basically, take all the preventive steps we've been told to do for months—wash our hands, stay six feet away from others, and wear face coverings when it's not possible to physically distance. And when a vaccine is available to you, get it. Still, Dr. Narasimhan warns that we don't know yet if those measures are as effective against B.1.1.7 as they were in an identical scenario with the regular strain of COVID-19. "We may need to amp up these measures at a time when society is already fatigued of them."
She adds that we simply won't know all the answers about B.1.1.7 for some time, and that goes for any other emerging new strain. "As health care workers and scientists, we were just seeing a light at the end of the pandemic tunnel with the vaccine rollout and this uncertainty is unsettling," she admits.
The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.
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