The delta variant of COVID-19 is currently raging throughout communities across the United States—particularly in the South—but it’s not the only strain of the disease that is wreaking havoc worldwide. The World Health Organization has identified four “variants of concern,” which it defines as variants that have shown to be either more transmissible, more harmful, or more capable of evading public health measures such as vaccines and therapies.

According to the WHO, four variants currently meet the standard: alpha, beta, gamma, and delta. Of course, most of us in the United States are very familiar with delta, which has been the dominant strain here since our summer wave began. But exactly how and when did delta and the other variants spread from their first known places of origin to become global menaces?

The folks at The BMJ medical journal are providing new insight this week with a breakdown of each of the variants along with a detailed description of when and where they did—and are still doing—the most damage. In an article published Thursday, The BMJ includes a color-coded animated map that tracks the spread of each variant from August 2020 through the first half of July 2021.

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