"Goldilocks virus": Delta vanquishes all variant rivals as scientists race to understand its tricks

With so many people unvaccinated, in the United States and around the world, the virus has abundant opportunity not only to spread and sicken large numbers of people, but to mutate further. Some scientists have expressed hope that the virus has reached peak “fitness,” but there is no evidence this is so.

“To see delta just running laps around these other strains is very concerning,” said Benjamin Neuman, a virologist with Texas A&M University. “It’s like ‘Jurassic Park,’ the moment you realize the dinosaurs have all got loose again.”

Delta’s meteoric takeover of the pandemic in the United States brought a jarring, premature end to a summer of relative freedom from the global viral emergency. Just as schools and workplaces were ready to hit reset and embrace a level of normalcy, indoor mask-wearing is back in much of the country, regardless of vaccination status.