Researchers said the variants are believed to be contributing to a recent spike of positive COVID-19 cases.
"You could think of it as America's most costly war. We've lost half a million people and it's not clear that we're winning the final battle here," said Dr. Frederic Bushman, Chair of Microbiology at Penn Medicine.
Bushman said viruses are always changing and that the coronavirus is no different. But what's alarming to him is that they have discovered a greater proportion of several fast-spreading, more contagious variants of the virus in the southeastern Pennsylvania.
"We saw some examples of the U.K. variant. There's a new variant out of California, another out of New York, which was quite prominent. There's pretty good evidence that these will change in ways to permit them to grow more efficiently on people," Bushman said.
The study also revealed that some variants are showing similarities and features seen in the variants out of South Africa and Brazil.
The threat of further spread is why Dr. Rochelle Walensky, Director of Centers for Disease Control and Prevention is making an emotional plea not to let up.
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"We have so much to look forward to, so much promise and potential for where we are, and so much reason for hope, but right now I'm scared," Walensky said. "I'm speaking today not only as your CDC Director, but as a wife, as a mother, as a daughter to ask you to just please hold on a little while longer."
Bushman agrees that the country is still in a dire situation and said enough people aren't vaccinated to beat the virus just yet.
"We're engaged in a really tough struggle, so everyone listening, you're soldiers in this war and there's much you can do. Wear a mask, get vaccinated when you can," Bushman said.
Penn researchers are continuing to track the spread of the variants as the virus evolves.