Washington: The United States has registered over 10,000 infection cases of Covid-19 variants as experts caution of another Covid-19 surge.

Among the total of 10,985 variant cases reported by the US Centers for Disease Control and Prevention (CDC) as of Sunday, 10,579 cases were caused by the variant known as B.1.1.7, which was originally detected in Britain, reports by Xinhua news.

The B.1.427 and B.1.429 variants, two coronavirus strains first detected in California, are also being closely monitored by the CDC. There were 288 cases of a new strain initially discovered in South Africa, called B.1.351, and 118 cases of the P.1 strain first discovered in Brazil.

The five coronavirus strains are currently classified by the CDC as "variants of concern," as evidence shows an increase in their transmissibility, increased hospitalizations or deaths, a significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures.

 Virus variants may contribute to "increased spread" of infections, Stanley Perlman, professor of microbiology and immunology at the University of Iowa, told Xinhua in an interview. "Cases may be increasing again. We need to still wear masks and practice social distancing," he noted.

Experts have repeatedly expressed concern that the country would face another surge in Covid-19 cases if Americans did not keep protective measures such as wearing masks, avoiding travel, and continuing social distancing until more people are vaccinated.

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