City health officials have outlined its plan for looking into the New York City variant that began spreading as early as November. They’re urging New Yorkers to keep wearing masks and get vaccinated as soon as possible to curb the outbreak.

Last week, researchers at Columbia University and CalTech announced findings of the new mutant called B.1.526. Though its threat level is unclear, the NYC variant has a genetic change that may dampen the effectiveness of the currently authorized vaccines based on a similar mutation seen in the variant from South Africa. Dr. Anthony Fauci, the nation’s top infectious disease official, said Monday the strain is being taken “very seriously” and told reporters it likely originated in Washington Heights.

The city’s public health advisor, Dr. Jay Varma, has been insisting for days that the B.1.526 variant is still one that scientists are looking into but is not of particular concern at this point. It is normal for viruses to mutate and change. On Wednesday, he said the city was going through lab records to learn more about the variant and added the new strain was found in various parts of the city and state.

“We are concerned not just about this variant but all of the ones that are circulating because it’s just a reminder that we continue to need to be persistent about all of the things we know prevent infection,” Varma told reporters during a press briefing. “This doesn’t change any of the things we are doing right now because again, we need to understand how these viruses evolve because there may be a time when we need to do something different, but that time is not right now.”

On Tuesday, the city Health Department gave an update on ongoing surveillance for the variants, citing that 7.9% of sequenced cases (65 of 824) were the United Kingdom variant, or B.1.1.7, during the week of February 15th. That was a 1.6% increase from the week prior. As of February 24th, there were 116 cases of the U.K. variant in city residents. Two cases of a strain first seen in South Africa—called the B.1.351—have also been detected.

“Our best defense for us is to knock it out early,” Varma said. “We can do this by stopping transmission with precautions like masks, distancing, washing hands, staying home if you’re ill, getting tested, and getting vaccinated when it’s your turn.”

Viral mutations are nothing new and happen regularly. During a technical briefing on Tuesday, Varma explained how any single variant rises to the level of causing concern for public health officials.

“What makes it a variant of concern? One is that it could change so much that it evades our usual tests,” he said, “Or it's changed so much that it evades our antibodies or our immune defenses, or it's changed so much that it causes more severe disease and death, or it has changed so much that it becomes more contagious.”

“The three variants of concern that you hear about in the news … are the ones that were first detected in the U.K., South Africa, and Brazil,” Varma said. “They all show some of these worrisome features.”