The fight against the virus that causes COVID-19 has taken a new turn: Reports of mutations are appearing quickly.

Many scientists fear that a variant of the new coronavirus may appear that cannot be prevented by a known treatment or vaccine.

The genes of the coronavirus are changing, and health officials say the high number of new cases is the main reason. Each new infection gives the virus a chance to mutate as it makes copies of itself. Each mutation threatens to undo the progress made in the last year of fighting the pandemic.

On Friday, the World Health Organization urged more efforts to find new variants. The U.S. Centers for Disease Control and Prevention said a new variant first identified in Britain a few months ago might become the number one virus in the U.S. by March. It does not cause more severe illness, but it could cause more hospitalizations and deaths. The CDC warned of coming "exponential growth."

"We're taking it really very seriously," Dr. Anthony Fauci said on American television Sunday. He is the U.S. government's top infectious disease expert.

"We need to do everything we can now...to get transmission as low as we possibly can," said Harvard University's Dr. Michael Mina. He said that the best way to stop mutations is to slow the spread of the virus.

So far, vaccines remain effective. There are, however, signs that some tests and drug treatments may not work with the new variants.

The virus may create a mutation that makes it more dangerous, said Dr. Pardis Sabeti. She is an evolutionary biologist at the Broad Institute of MIT and Harvard.

For example, younger people may not be afraid of the virus because it does not make them very sick. That could change quickly, she warned.

More reports of mutations

It is normal for viruses to mutate. A mutation that strengthens the virus helps it to survive by pushing out the weaker variants.

Just a few months after the coronavirus was discovered, a mutation called D614G began to spread. It quickly became a major form of the virus.

Trevor Bedford is a biologist with the Fred Hutchinson Cancer Research Center in Seattle. Last week, he wrote on Twitter, now, "we've started to see some striking evolution" of the virus.

New variants have also been found in South Africa and Brazil. A main mutation in the variant identified in Britain appears to be in another variant that was found in Ohio, said Dan Jones. He is a molecular pathologist at Ohio State University who announced that finding last week.

This is important because it does not appear the mutation was created as the result of travel. Rather, the virus may mutate in the same way in different places, Jones said.

That also means that travel restrictions might be ineffective, Mina said. Because the United States has so many cases, "we can breed our own variants that are just as bad or worse" as those in other countries, he said.

Treatment, vaccine, reinfection risks

Government scientists are "actively looking" into the possibility that variants found in South Africa and Brazil may be able to fight off antibody drugs and other treatments that can help people survive COVID-19, Dr. Janet Woodcock of the U.S. Food and Drug Administration told reporters Thursday.

Other scientists are not as worried. Dr. Andrew Pavia of the University of Utah said vaccines in use now should remain effective. They may need a small change to fight mutations.

Even then, he said, "it's probably going to be on the order of years if we use the vaccine well rather than months." He was speaking Thursday on a webcast run by the Infectious Diseases Society of America.

I'm Susan Shand.

The Associated Press reported this story. Susan Shand adapted it for Learning English. Mario Ritter, Jr. was the editor.

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mutate – v. to cause a change that creates a different quality in a living thing

variant – n. different in some way from others of the same kind

exponential – adj. very fast, to a very great degree

transmission – n. the process of something spreading, going from one place to another

evolution – n. the process by which living things change over time

pathologist – n. a part of medicine that seeks to find out causes