Coronavirus live updates: U.S. coronavirus cases approach 50 million

But public health experts nationwide are stressing that the overwhelming majority of the nation’s coronavirus cases are still caused by the highly transmissible delta variant, which has led to some of the worst spikes of the pandemic. By early Tuesday, the United States had tallied nearly 49.3 million coronavirus cases since the first infection surfaced in January 2020, according to Washington Post tracking, and more than 786,000 deaths.