It’s also important to note the variant is adapting. In addition to changes in COVID-19 symptoms, it’s also much quicker. To give an example, the Alpha variant, the first mutation, spread 50% quicker than the original virus. Delta, meanwhile, spreads 40 to 60% quicker than Alpha. “It binds to the human receptor with higher affinity than does the alpha variant,” UVA infectious disease expert William Petri said.