Washington, Jul 20, 2021, SPA -- The Delta variant now is estimated to comprise 83 percent of all sequenced Covid-19 cases in the United States, the director of the Centers for Disease Control and Prevention (CDC) said Tuesday. "This is a dramatic increase, up from 50 percent the week of July 3," Doctor Rochelle Walensky said during a Senate hearing. The surge in Delta cases - almost exclusively among unvaccinated Americans - is leading to more deaths. COVID fatalities have risen by nearly 48 percent over the past week to an average of 239 per day, Walensky said. "Each death is tragic and even more heartbreaking when we know that the majority of these deaths could be prevented with a simple, safe, available vaccine," the CDC chief said. Walensky said nearly two-thirds of the counties in the United States - mostly in rural areas - have vaccinated less than 40 percent of their residents, "allowing for the emergence and rapid spread of the highly transmissible Delta variant." --SPA 21:16 LOCAL TIME 18:16 GMT 0036 www.spa.gov.sa/w1588999