Another delta mutation — also found in kappa and epsilon — is called L452R. Experiments suggest this mutation, which also affects the receptor-binding domain, acts to prevent antibodies from neutralizing the virus, Cooper said. These mutations appear to be more formidable as a team than alone.
The genetic changes “are certainly doing something, but why that combination makes the delta variant more fit is not entirely obvious,” Bedford said. “Putting them together seems to matter.” Delta also has developed genetic changes not seen in other variants. One such spike mutation is called D950N. “This might be unique,” Cooper said. “We don’t see that anywhere else.”
The D950N mutation is different than other mutations because it’s located outside the receptor-binding domain in an area of the coronavirus genome that helps the virus fuse with human cells, Cooper said. Fusing with human cells allows the coronavirus to dump its genetic material into those cells.
This mutation could affect which types of cells the virus infects, potentially allowing it to harm different organs and tissues. Mutations in this region are also associated with higher viral loads, Cooper said.
Delta also contains mutations in a part of the spike protein called the N-terminal domain, which provides a “supersite” for antibodies to latch onto the virus and prevent it from entering cells, said Dr. Hana Akselrod, an infectious diseases specialist at the George Washington University School of Medicine & Health Sciences.
Mutations in this region make monoclonal antibodies less effective in treating covid and increases the delta variant’s ability to escape vaccine-generated antibodies, Akselrod said. That may explain why vaccinated people are slightly more likely to become infected with delta, causing mostly mild illness but allowing them to transmit the virus.
Scientists say it’s impossible to predict exactly how delta will behave in the future, although Topol said, “It’s going to get worse.”
Topol noted that delta outbreaks tend to last 10 to 12 weeks, as the virus “burns through” susceptible populations.