New CDC study details cluster of breakthrough infections tied to July Fourth celebrations

ATLANTA - Kaiser Permanente Georgia epidemiologist Dr. Felipe Lobelo says masking up indoors in public may be more important than ever, now that the US is contending with a COVID-19 variant that appears more contagious, and may be more severe, than earlier strains.

Friday, the Georgia Department of Public Health appealed to residents to get vaccinated, saying daily case numbers are up 204% from where they were two weeks ago.

Thursday, new cases totaled 4,612, the highest daily number since mid-February, and hospitalizations are up by 50% in the last 14 days.
Deaths have also risen 18% in the last two weeks.

Only 40% of Georgians are fully vaccinated.

A confidential CDC memo warns the delta variant may spread as easily as chickenpox and could be causing as many as 35,000 breakthrough infections a week among162 million Americans who are fully immunized. 

"With the delta variant, it's pretty clear there is a higher viral load, meaning that there are more viral particles, particularly in the nose and the mouth that are transmitting if we are going to be in close contact, or (they) are even lingering in the air," Dr. Lobelo says. 

That higher viral load,  Dr. Lobelo says, means the virus needs less time and close contact to move from one person to another.

"The likelihood of that virus catching into my nose, my mouth, my mucous, is going to be much higher than what we knew with the previous versions of the virus," he says.

While the CDC stresses unvaccinated Americans are driving the surge in infections across the US, a new case study shows fully immunized Americans can be infected and spread the virus, too.

The report, published in the CDC's Morbidity and Mortality Weekly Report (MMWR), details an investigation of 469 COVID-19 cases tied to a series of large Fourth of July gatherings along the Massachusetts coast.

Among the infections in Massachusetts residents, 346 (74%) occurred in people who were fully vaccinated.

Of those breakthrough infections, 274 (79%) reported signs or symptoms, such as cough, headache, sore throat, muscle aches and fever.

When samples taken from those infected were tested, the unvaccinated and vaccinated individuals had similar levels of virus in their bodies, the report found.

In a statement released Friday, CDC Director Dr. Rochelle Walensky wrote,  "High viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with Delta can transmit the virus. This finding is concerning and was a pivotal discovery leading to CDC’s updated mask recommendation. The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones."

Dr. Lobelo, who says he has continued to wear a mask in indoor public settings throughout the pandemic, says the findings drive home the importance of masking up in high-transmission areas.

"I think it's even more clear now that everyone who is vaccinated is going to benefit personally from using indoor masks, because you're going to still be at risk of catching this virus, transmitting this virus, and potentially having some mild symptoms," he says. 

Dr. Lobelo masking use is especially important for parents with children too young to be vaccinated or anyone who is around someone with a weakened immune system.

If you are not vaccinated, he says, now is the time.

"We've seen an increase in cases 10-fold, in just a couple of weeks, and that is going to increase," he says . "It's clear that, for the foreseeable future, we are going to expect more hospitalizations, more cases."

If you have not been been vaccinated, he says, you risk of infection has never been higher.

"There is so much transmissibility in this virus, that you're either going to be protected and mount an immune response, because you got vaccinated, or you'll probably be exposed to this virus." Dr. Lobelo says.  "Like I said before, sometimes it's a Russian roulette.  We don't know who is going to develop severe cases of COVID."

WATCH: FOX 5 Atlanta live news coverage

_____

Sign up for FOX 5 email alerts

Download the FOX 5 Atlanta app for breaking news and weather alerts.