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Medical experts say SARS-CoV-2, like all viruses, constantly changing

A nurse prepares syringes at an Italian Red

A nurse prepares syringes at an Italian Red Cross anti-COVID-19 vaccination hub in Rome on Monday. Italy was reinforcing checks at borders and going through lists of airline passengers who arrived in Italy in the last two weeks after a business traveler returning from Mozambique tested positive for the new omicron variant. Credit: AP/Gregorio Borgia

The emergence of another troubling variant of the virus that causes COVID-19 is no surprise, infectious disease experts said Monday.

Epidemiologists are watching for the omicron variant, first detected in South Africa last week, though the highly contagious delta variant is still to blame for the majority of COVID-19 infections in the United States. Scientists are trying to determine how quickly the variant spreads, if it causes more serious illness and how effectively the current COVID-19 vaccines and boosters protect against it.

SARS-CoV-2, like all viruses, is constantly changing, said Dr. Betty Diamond, director of the Institute of Molecular Medicine at the Feinstein Institutes for Medical Research in Manhasset.

"Viruses mutate all the time randomly, and those that are best at infecting a host or evading a host’s immune system propagate best and take off in the population," she said. "Some viruses mutate more than others. SARS-CoV-2 mutates a lot."

When SARS CoV-2 replicates, it creates mutations, explained Dr. Stanley H. Weiss, infectious and chronic disease epidemiologist and professor at the Rutgers New Jersey Medical School and the Rutgers School of Public Health.

"Most of the mutations are fatal to the virus, and so it doesn't survive, but some mutations can give it advantages over other viruses," he said. "When one of those occurs, then we see what we call a variant of the virus."

Scientists monitor the impact of variants on the human population by looking at samples and examining genetic sequencing, Weiss said. In laboratories, they try to determine the impact of the variants on medications and also how a person’s immune systems will react to the variants.

"It appears that there are some people who are able to be infected with the virus for a prolonged period of time in their body, giving the virus a chance to evolve … particularly in some people who are immune-suppressed," Weiss said. "In addition, we have a virus spreading quite rapidly in many parts of the world where small fractions of the population have been vaccinated. So the chance for yet further variants to occur is extremely likely."

According to the Centers for Disease Control and Prevention, 10 variants of the virus are being monitored, along with the delta variant.

"Clearly the earlier variants had relatively few number of documented mutations," said Dr. Bruce Farber, chief of infectious diseases at Long Island Jewish Medical Center and North Shore University Hospital. "And this variant has an enormous number. I think it is many more than 25.

"The more mutations, the more likely you are going to evade whatever you had from previous vaccinations," he added. "And that’s why it is alarming."

Medical experts are recommending booster shots to guard against omicron, or to get initial shots.

The original "variant that was circulating a year ago, on average, infected 2.5 people," said Dr. Bettina Fries, chief of the Division of Infectious Diseases at Stony Brook Medicine. "The delta virus infects seven people … the virus spreads much faster and much more efficiently."

Weiss credited clinicians and scientists in South Africa for quickly identifying the omicron variant, compared with how surveillance was conducted in the past.

"Similar degrees of surveillance are not being done in most other countries, and the risk that there could be other variants out there [that] we don't yet know about is quite possible," he said. "This emphasizes why we've been talking about this as a global pandemic and the essential nature of getting vaccinations around the world."

With Bart Jones

What to know

Viruses, including the SARS CoV-2 virus that causes COVID-19 mutate, causing variants to occur. This is common, experts say, and will continue.

The CDC is monitoring 10 variants of the SARS CoV-2 virus, along with the highly contagious delta variant, which is responsible for most of the infections in the U.S.

The best way to prevent serious illness from the variants of COVID-19 is to get vaccinated and for fully vaccinated people to get booster shots.