Delta variant fundamentals: The Delta variant now accounts for more than more than 90% of new infections, according to the CDC. Delta is also believed to be the most transmissible strain of COVID-19 yet. CDC mapping shows the Delta variant was preceded by Alpha (B.1.1.7) that was first detected in the U.S. in December 2020. Beta followed (B.1.351) in January. Gamma (P.1) also was found in the U.S. in January. Delta (B.1.617.2) was identified in the U.S. in March 2021. 'The Delta variant isn't just one kind of COVID, it's actually a group of strains that have some common features,' said Mary Rodgers, principal scientist and member of the Abbott Pandemic Defense Coalition. 'Some mutations of the Delta variant are found in other strains as well, but it's the combination that is unique.' A recent study backs Rodgers' assessment. It found that, 'After months of data collection, scientists agree: The delta variant is the most contagious version of the coronavirus worldwide. It spreads about two to three times faster than the original version of the virus, and it's currently dominating the outbreak in the United States.' While doctors treating the recent resurgence of COVID infections have noted those impacted by the Delta variant tend to be 'younger, sicker, quicker,' infection rates also are impacted by choices such as not wearing masks nor social distancing, as well as lower vaccination rates in hardest-hit areas. 'Delta is clearly linked to having the ability to escape from immune responses, having increased transmissibility, and can infect vaccinated people and spread more easily,' Rodgers said. 'Individual changes to the virus are coming faster than expected due to increased numbers of infection, giving the virus more chances to mutate.' Still more research is needed. 'Some variations allow the virus to spread more easily or make it resistant to treatments or vaccines,' the CDC reported. 'Those variants must be monitored more carefully.'