Since first appearing in India in late 2020, the Delta variant of SARS-CoV-2 has become the predominant strain in much of the world. According to current estimates, the Delta variant could be more than twice as transmissible as the original strain of SARS-CoV-2. Researchers then compared participants’ infection patterns with those of 63 people who contracted the original SARS-CoV-2 strain in 2020. Individuals infected with Delta also had viral loads up to 1,260 times higher than those in people infected with the original strain. A number of other questions about the Delta variant remain unanswered.