THE Delta variant strain of Covid-19 is causing a severe uptick in infection cases throughout the United States. The highly-contagious variant is accounting for over 80 percent of the nation's Covid-19 cases, according to Centers for Disease Control and Prevention data. How do they test for the Covid-19 Delta variant? Although there is no specific test for the Delta variant, it’s likely a positive Covid-19 result indicates you could be infected with the variant, according to Human and Health Services of Texas. The reason is because the majority of Covid cases in the United States are the Delta variant.