Why delta is the most transmissible variant yet: 9 things to know

The COVID-19 delta variant contains genetic changes that allow it to spread twice as fast as the original strain, Kaiser Health News reported.

Nine things to know, per KHN: 

1. Delta has an incubation period of four days versus six, which means infected individuals are contagious sooner. 

2. People infected with delta infect six people on average, compared to an average of two to three people in the early days of the pandemic.

3. The delta variant isn't necessarily more lethal than other variants, but it has the potential to kill more people because it infects so many more, said Eric Topol, MD, cardiologist and founder and director of the Scripps Research Translational Institute.

4. Like all known circulating variants, delta contains the spike mutation D614G, which scientists think makes it easier for the virus to enter cells.

5. Delta also has the spike mutation P681R, which resembles a mutation in the alpha variant that seems to produce higher viral loads in patients, said Vaughn Cooper, PhD, professor of microbiology and molecular genetics at the University of Pittsburgh. Individuals infected with delta have 1,000 times higher viral load, making them more likely to spread the virus when they sneeze, cough or talk.

6. The delta mutation L452R — also found in kappa and epsilon — is thought to prevent antibodies from neutralizing the virus, Dr. Cooper said.

7. Delta also has genetic changes not seen in other variants.

8. Outbreaks tied to delta tend to last 10-12 weeks, as the virus "burns through" susceptible populations, Dr. Topol said. 

9. COVID-19 vaccines remain mostly effective against the delta variant.

By failing to contain COVID-19, people are allowing the virus to continue mutating into increasingly dangerous forms, said William Haseltine, PhD, a former Harvard professor who helped design HIV/AIDS treatments.

"It's getting better, and we're making it better," Dr. Haseltine said. "Having half the population vaccinated and half unvaccinated and unprotected — that is the exact experiment I would design if I were a devil and trying to design a vaccine-busting virus."


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