COVID-19 variant cases are on the rise in Texas. Here’s what you need to know.

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Last winter, health experts worried about COVID-19 variants spreading quickly across the state, further overwhelming already crammed intensive care units. While health officials remain concerned about the potential for a wider outbreak fueled by more contagious variants, new case averages, hospitalizations and deaths are still trending down in Texas as the number of people fully vaccinated statewide has passed 25%.

Nationwide, the average weekly number of new COVID-19 cases has dropped in more than half of states as 29% of Americans are now fully vaccinated.

While COVID-19 started out as one strain, it has since spawned dozens of recorded mutations, said Benjamin Neuman, a virologist and professor at Texas A&M University.

Variants are a concern because some spread more easily, may cause severe illness in more people and could be resistant to current treatments for COVID-19. Some experts worry that as more mutations pop up, hospitalizations and deaths may rise as well. The U.S. Centers for Disease Control and Prevention says vaccines and other preventive measures like social distancing and mask-wearing should protect people from variants.

Here’s what you need to know about COVID-19 variants in Texas:

Which variants are being tracked by the state?

The most dominant strain in Texas and the country is currently the B.1.1.7 variant from the United Kingdom, first detected in the United States in December. The CDC has also listed mutations first discovered in California, South Africa and Brazil as variants of concern. So far in Texas, cases of the five CDC variants of concern have slowly increased since the winter: more than 2,000 variant cases have been reported to the Department of State Health Services as of April 29, though the actual number may be higher, said Jennifer Shuford, the chief state epidemiologist. In early March, Houston became the first city in the state to report at least one case of each variant of concern.

The first variant to be publicly identified and reported out of Texas, the Brazos Valley variant, was discovered by Texas A&M scientists in mid-April. Neuman said they identified three Brazos Valley mutations — BV-1, BV-2 and BV-3 — of which only five cases have been reported.