These are Insider's biggest healthcare stories for September 9.
Like Delta, the variants show signs of being highly transmissible, resistant to the body's immune defenses, or both.
The Mu variant could have the ability to evade the immunity people get from vaccines and past infections, according to the World Health Organization.
These are Insider's biggest healthcare stories for August 30.
Sequencing tests, which pick up on variants, have be federally approved before their results can be disclosed to doctors or patients.
In an interview with Insider's EIC, Rochelle Walensky said she feared the unlikely possibility that the coronavirus could mutate to evade vaccines.
These are Insider's biggest healthcare stories for August 9.
One of the Republicans he suggested was Florida Gov. Ron DeSantis, whose state is facing record COVID-19 hospitalizations for the third day in a row.
As cases of the Delta variant surge, vaccinated people who don't mask up may increase the risk that vaccine-resistant variants develop, a study says.
People who are fully vaccinated can spread the Delta variant just as easily as those who are unvaccinated, according to an internal CDC document.
Two young people who were vaccinated and got mild COVID-19 breakthrough cases described to Insider how their symptoms progressed.
Experts worry about breakthrough cases in older people or those who are immunocompromised, or the virus mutating into a more dangerous strain.
This table shows the important differences between COVID-19 vaccines from Pfizer-BioNTech, Moderna, Johnson & Johnson, and AstraZeneca.
"The more unvaccinated people there are, the more opportunities for the virus to multiply," infectious disease expert Dr. William Schaffner said.
The CDC stopped monitoring non-severe breakthrough cases among vaccinated people in May. That data could have helped experts assess Delta's risk.
Coronavirus transmission will likely increase in these areas as the Delta variant spreads, CDC Director Rochelle Walensky said.
The Alpha variant took over as the US's dominant coronavirus strain in April. Delta could replace it soon.